Blame for chemistry.jsonl

{"answer": "One mole contains exactly 6.022 x 10^23 particles, linking atomic-scale mass to grams chemists can weigh.", "choices": null, "id": "che_0001", "kind": "concept", "lang": "en", "question": "What is a mole in chemistry?", "steps": ["Define the mole as the SI amount unit.", "Give Avogadro's number: 6.022 x 10^23 per mole.", "Note molar mass converts moles to grams."], "subject": "chemistry", "text": "Answer: 6.022 x 10^23 particles.\nSteps:\n1. Define the mole as the SI amount unit.\n2. Give Avogadro's number: 6.022 x 10^23 per mole.\n3. Note molar mass converts moles to grams.", "topic": "stoichiometry"}
{"answer": "There are 2.00 mol of water, from 36.0 g divided by 18.015 g/mol.", "choices": null, "id": "che_0002", "kind": "worked_example", "lang": "en", "question": "How many moles are in 36.0 g of water (M = 18.015 g/mol)?", "steps": ["Write: n = mass / molar mass.", "Substitute: 36.0 / 18.015.", "n = 2.00 mol."], "subject": "chemistry", "text": "Answer: 2.00 mol.\nSteps:\n1. Write: n = mass / molar mass.\n2. Substitute: 36.0 / 18.015.\n3. n = 2.00 mol.", "topic": "stoichiometry"}
{"answer": "The molar mass of CO2 is 44.01 g/mol, from 12.01 plus twice 16.00.", "choices": {"A": "28.01 g/mol", "B": "32.00 g/mol", "C": "44.01 g/mol", "D": "18.02 g/mol"}, "id": "che_0003", "kind": "multiple_choice", "lang": "en", "question": "What is the molar mass of carbon dioxide?", "steps": ["Add C: 12.01.", "Add two O: 2 x 16.00 = 32.00.", "Total 44.01; select C."], "subject": "chemistry", "text": "Answer: 44.01 g/mol.\nSteps:\n1. Add C: 12.01.\n2. Add two O: 2 x 16.00 = 32.00.\n3. Total 44.01; select C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "Mol je jednotka látkového množství obsahující 6,022 x 10^23 částic, což spojuje atomové hmotnosti s gramy.", "choices": null, "id": "che_0004", "kind": "concept", "lang": "cs", "question": "Co je mol (látkové množství)?", "steps": ["Definuj mol jako jednotku SI.", "Uveď Avogadrovu konstantu 6,022 x 10^23.", "Vysvětli převod přes molární hmotnost."], "subject": "chemistry", "text": "Answer: 6,022 x 10^23 částic.\nSteps:\n1. Definuj mol jako jednotku SI.\n2. Uveď Avogadrovu konstantu 6,022 x 10^23.\n3. Vysvětli převod přes molární hmotnost.", "topic": "stoichiometry"}
{"answer": "The mass is 146.1 g, from 2.50 mol times 58.44 g/mol.", "choices": null, "id": "che_0005", "kind": "worked_example", "lang": "en", "question": "What mass is 2.50 mol of NaCl (M = 58.44 g/mol)?", "steps": ["Write: mass = n x M.", "Substitute: 2.50 x 58.44.", "Mass = 146.1 g."], "subject": "chemistry", "text": "Answer: 146.1 g.\nSteps:\n1. Write: mass = n x M.\n2. Substitute: 2.50 x 58.44.\n3. Mass = 146.1 g.", "topic": "stoichiometry"}
{"answer": "Oxygen is limiting because 1 mol O2 needs 2 mol H2 but 4 mol H2 are present, so at most 2 mol H2O form.", "choices": {"A": "H2 is limiting", "B": "O2 is limiting", "C": "Both limit equally", "D": "Neither limits"}, "id": "che_0006", "kind": "multiple_choice", "lang": "en", "question": "For 2H2 + O2 -> 2H2O with 4 mol H2 and 1 mol O2, which reactant limits?", "steps": ["Need ratio H2:O2 = 2:1.", "Have ratio 4:1, excess H2.", "Select option B."], "subject": "chemistry", "text": "Answer: O2 is limiting.\nSteps:\n1. Need ratio H2:O2 = 2:1.\n2. Have ratio 4:1, excess H2.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Balancing enforces conservation of mass so each element has equal atom counts on both sides of the equation.", "choices": null, "id": "che_0007", "kind": "concept", "lang": "en", "question": "Why must chemical equations be balanced?", "steps": ["State conservation of mass.", "Require equal atoms per element both sides.", "Adjust coefficients, never subscripts."], "subject": "chemistry", "text": "Answer: To conserve atoms of each element.\nSteps:\n1. State conservation of mass.\n2. Require equal atoms per element both sides.\n3. Adjust coefficients, never subscripts.", "topic": "stoichiometry"}
{"answer": "Ve 44 g CO2 je 1,00 mol, protože 44 děleno 44,01 se rovná 1,00.", "choices": null, "id": "che_0008", "kind": "worked_example", "lang": "cs", "question": "Kolik molů je ve 44 g CO2 (M = 44,01 g/mol)?", "steps": ["Napiš vzorec: n = m / M.", "Dosaď: 44 / 44,01.", "n = 1,00 mol."], "subject": "chemistry", "text": "Answer: 1,00 mol.\nSteps:\n1. Napiš vzorec: n = m / M.\n2. Dosaď: 44 / 44,01.\n3. n = 1,00 mol.", "topic": "stoichiometry"}
{"answer": "Percent yield is 80%, from 40 g actual divided by 50 g theoretical times 100.", "choices": {"A": "60%", "B": "70%", "C": "80%", "D": "90%"}, "id": "che_0009", "kind": "multiple_choice", "lang": "en", "question": "Theoretical yield is 50 g and actual yield is 40 g. What is the percent yield?", "steps": ["Write: actual / theoretical x 100.", "Substitute: 40 / 50 x 100 = 80.", "Select option C."], "subject": "chemistry", "text": "Answer: 80%.\nSteps:\n1. Write: actual / theoretical x 100.\n2. Substitute: 40 / 50 x 100 = 80.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "The empirical formula gives the simplest whole-number atom ratio while the molecular formula gives the true atom counts.", "choices": null, "id": "che_0010", "kind": "concept", "lang": "en", "question": "How do empirical and molecular formulas differ?", "steps": ["Define empirical as simplest ratio.", "Define molecular as actual counts.", "Give glucose: CH2O versus C6H12O6."], "subject": "chemistry", "text": "Answer: Simplest ratio versus true counts.\nSteps:\n1. Define empirical as simplest ratio.\n2. Define molecular as actual counts.\n3. Give glucose: CH2O versus C6H12O6.", "topic": "stoichiometry"}
{"answer": "There are 3.011 x 10^23 atoms, from 0.500 mol times 6.022 x 10^23 per mole.", "choices": null, "id": "che_0011", "kind": "worked_example", "lang": "en", "question": "How many atoms are in 0.500 mol of iron?", "steps": ["Write: N = n x Avogadro.", "Substitute: 0.500 x 6.022 x 10^23.", "N = 3.011 x 10^23 atoms."], "subject": "chemistry", "text": "Answer: 3.011 x 10^23 atoms.\nSteps:\n1. Write: N = n x Avogadro.\n2. Substitute: 0.500 x 6.022 x 10^23.\n3. N = 3.011 x 10^23 atoms.", "topic": "stoichiometry"}
{"answer": "Molární hmotnost je hmotnost jednoho molu látky v g/mol, číselně rovná relativní molekulové hmotnosti.", "choices": null, "id": "che_0012", "kind": "concept", "lang": "cs", "question": "Co je molární hmotnost?", "steps": ["Definuj hmotnost 1 molu.", "Jednotka g/mol.", "Příklad: voda 18,015 g/mol."], "subject": "chemistry", "text": "Answer: Hmotnost 1 molu v g/mol.\nSteps:\n1. Definuj hmotnost 1 molu.\n2. Jednotka g/mol.\n3. Příklad: voda 18,015 g/mol.", "topic": "stoichiometry"}
{"answer": "The balanced equation is CH4 + 2O2 -> CO2 + 2H2O, with coefficients 1, 2, 1, 2.", "choices": {"A": "1, 1, 1, 1", "B": "1, 2, 2, 1", "C": "2, 2, 1, 2", "D": "1, 2, 1, 2"}, "id": "che_0013", "kind": "multiple_choice", "lang": "en", "question": "What coefficients balance CH4 + O2 -> CO2 + H2O?", "steps": ["Balance C: 1 each side.", "Balance H with 2 H2O.", "Balance O with 2 O2; select D."], "subject": "chemistry", "text": "Answer: 1, 2, 1, 2.\nSteps:\n1. Balance C: 1 each side.\n2. Balance H with 2 H2O.\n3. Balance O with 2 O2; select D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "The volume is 44.8 L, from 2.00 mol times 22.414 L/mol at STP.", "choices": null, "id": "che_0014", "kind": "worked_example", "lang": "en", "question": "What volume does 2.00 mol of ideal gas occupy at STP (22.414 L/mol)?", "steps": ["Write: V = n x molar volume.", "Substitute: 2.00 x 22.414.", "V = 44.8 L."], "subject": "chemistry", "text": "Answer: 44.8 L.\nSteps:\n1. Write: V = n x molar volume.\n2. Substitute: 2.00 x 22.414.\n3. V = 44.8 L.", "topic": "stoichiometry"}
{"answer": "Limitující reaktant se spotřebuje jako první a určuje maximální množství produktu.", "choices": null, "id": "che_0015", "kind": "concept", "lang": "cs", "question": "Co je limitující reaktant?", "steps": ["Definuj reaktant spotřebovaný první.", "Určuje maximální výtěžek.", "Ostatní jsou v nadbytku."], "subject": "chemistry", "text": "Answer: Reaktant určující maximální výtěžek.\nSteps:\n1. Definuj reaktant spotřebovaný první.\n2. Určuje maximální výtěžek.\n3. Ostatní jsou v nadbytku.", "topic": "stoichiometry"}
{"answer": "The concentration is 0.25 M, from 0.500 mol divided by 2.00 L.", "choices": {"A": "0.25 M", "B": "0.50 M", "C": "1.00 M", "D": "4.00 M"}, "id": "che_0016", "kind": "multiple_choice", "lang": "en", "question": "What is the molarity of 0.500 mol dissolved in 2.00 L?", "steps": ["Write: M = n / V.", "Substitute: 0.500 / 2.00 = 0.25.", "Select option A."], "subject": "chemistry", "text": "Answer: 0.25 M.\nSteps:\n1. Write: M = n / V.\n2. Substitute: 0.500 / 2.00 = 0.25.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "Dilute to 300 mL total by adding 200 mL water, since 100 mL x 6 M / 2 M = 300 mL.", "choices": null, "id": "che_0017", "kind": "worked_example", "lang": "en", "question": "How to dilute 100 mL of 6.0 M stock to 2.0 M?", "steps": ["Use M1V1 = M2V2.", "V2 = 100 x 6.0 / 2.0 = 300 mL.", "Add 300 - 100 = 200 mL water."], "subject": "chemistry", "text": "Answer: Add 200 mL water to reach 300 mL.\nSteps:\n1. Use M1V1 = M2V2.\n2. V2 = 100 x 6.0 / 2.0 = 300 mL.\n3. Add 300 - 100 = 200 mL water.", "topic": "stoichiometry"}
{"answer": "Avogadro's law states equal gas volumes at equal temperature and pressure contain equal numbers of molecules.", "choices": null, "id": "che_0018", "kind": "concept", "lang": "en", "question": "What is Avogadro's law?", "steps": ["Fix temperature and pressure.", "Volume scales with moles.", "All ideal gases share molar volume."], "subject": "chemistry", "text": "Answer: Equal volumes hold equal molecule counts.\nSteps:\n1. Fix temperature and pressure.\n2. Volume scales with moles.\n3. All ideal gases share molar volume.", "topic": "stoichiometry"}
{"answer": "Dva moly vody váží 36 g, protože 2 krát 18,015 se rovná 36,03.", "choices": {"A": "9 g", "B": "18 g", "C": "36 g", "D": "44 g"}, "id": "che_0019", "kind": "multiple_choice", "lang": "cs", "question": "Kolik gramů váží 2 moly vody?", "steps": ["Vynásob: 2 x 18,015 = 36,03.", "Zaokrouhli na 36 g.", "Vyber možnost C."], "subject": "chemistry", "text": "Answer: 36 g.\nSteps:\n1. Vynásob: 2 x 18,015 = 36,03.\n2. Zaokrouhli na 36 g.\n3. Vyber možnost C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "A Bronsted-Lowry acid donates a proton while a base accepts one, forming conjugate pairs.", "choices": null, "id": "che_0020", "kind": "concept", "lang": "en", "question": "What is the Bronsted-Lowry definition of acids and bases?", "steps": ["Define acid as proton donor.", "Define base as proton acceptor.", "Link pairs like HCl/Cl-."], "subject": "chemistry", "text": "Answer: Acids donate, bases accept protons.\nSteps:\n1. Define acid as proton donor.\n2. Define base as proton acceptor.\n3. Link pairs like HCl/Cl-.", "topic": "acids_bases"}
{"answer": "The conjugate base of H2SO4 is HSO4-, formed by losing one proton.", "choices": {"A": "SO4(2-)", "B": "HSO4(-)", "C": "H3SO4(+)", "D": "OH(-)"}, "id": "che_0021", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate base of sulfuric acid (H2SO4)?", "steps": ["Remove one H+ from H2SO4.", "Result is HSO4-.", "Select option B."], "subject": "chemistry", "text": "Answer: HSO4-.\nSteps:\n1. Remove one H+ from H2SO4.\n2. Result is HSO4-.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "The pH is 2.00, from -log(0.010) for the strong acid HCl.", "choices": null, "id": "che_0022", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.010 M HCl.", "steps": ["HCl dissociates fully: [H+] = 0.010 M.", "Write: pH = -log[H+].", "pH = -log(0.010) = 2.00."], "subject": "chemistry", "text": "Answer: 2.00.\nSteps:\n1. HCl dissociates fully: [H+] = 0.010 M.\n2. Write: pH = -log[H+].\n3. pH = -log(0.010) = 2.00.", "topic": "acids_bases"}
{"answer": "pH je záporný dekadický logaritmus koncentrace iontů H+, takže pH 7 je neutrální.", "choices": null, "id": "che_0023", "kind": "concept", "lang": "cs", "question": "Co je pH a jak se počítá?", "steps": ["Definuj pH = -log[H+].", "Pod 7 kyselé, nad 7 zásadité.", "Příklad: 0,01 M HCl má pH 2."], "subject": "chemistry", "text": "Answer: Záporný logaritmus [H+].\nSteps:\n1. Definuj pH = -log[H+].\n2. Pod 7 kyselé, nad 7 zásadité.\n3. Příklad: 0,01 M HCl má pH 2.", "topic": "acids_bases"}
{"answer": "HCl is the strong acid because it dissociates fully, unlike the weak acids listed.", "choices": {"A": "HCl", "B": "CH3COOH", "C": "H2CO3", "D": "NH4(+)"}, "id": "che_0024", "kind": "multiple_choice", "lang": "en", "question": "Which of these is a strong acid?", "steps": ["Recall strong acids dissociate fully.", "Eliminate acetic, carbonic, ammonium.", "Select option A."], "subject": "chemistry", "text": "Answer: HCl.\nSteps:\n1. Recall strong acids dissociate fully.\n2. Eliminate acetic, carbonic, ammonium.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "Neutralization combines H+ and OH- into water while the counterions form a salt.", "choices": null, "id": "che_0025", "kind": "concept", "lang": "en", "question": "What happens in a neutralization reaction?", "steps": ["Combine H+ with OH- to make water.", "Pair remaining ions as salt.", "Example: HCl + NaOH -> NaCl + H2O."], "subject": "chemistry", "text": "Answer: Acid plus base give salt and water.\nSteps:\n1. Combine H+ with OH- to make water.\n2. Pair remaining ions as salt.\n3. Example: HCl + NaOH -> NaCl + H2O.", "topic": "acids_bases"}
{"answer": "At 25 C the sum pH + pOH equals 14, so each can be found from the other.", "choices": null, "id": "che_0026", "kind": "concept", "lang": "en", "question": "How are pH and pOH related?", "steps": ["Define pOH = -log[OH-].", "Use Kw: pH + pOH = 14 at 25 C.", "Convert: pH = 14 - pOH."], "subject": "chemistry", "text": "Answer: pH + pOH = 14 at 25 C.\nSteps:\n1. Define pOH = -log[OH-].\n2. Use Kw: pH + pOH = 14 at 25 C.\n3. Convert: pH = 14 - pOH.", "topic": "acids_bases"}
{"answer": "The hydrogen ion concentration is 3.16 x 10^-4 M, from 10 raised to -3.50.", "choices": null, "id": "che_0027", "kind": "worked_example", "lang": "en", "question": "A solution has pH 3.50. Compute [H+].", "steps": ["Write: [H+] = 10^(-pH).", "Substitute: 10^(-3.50).", "[H+] = 3.16 x 10^-4 M."], "subject": "chemistry", "text": "Answer: 3.16 x 10^-4 M.\nSteps:\n1. Write: [H+] = 10^(-pH).\n2. Substitute: 10^(-3.50).\n3. [H+] = 3.16 x 10^-4 M.", "topic": "acids_bases"}
{"answer": "A buffer pairs a weak acid with its conjugate base to resist pH change.", "choices": {"A": "Strong acid plus strong base", "B": "Weak acid only", "C": "Salt only", "D": "Weak acid plus conjugate base"}, "id": "che_0028", "kind": "multiple_choice", "lang": "en", "question": "Which mixture forms a buffer?", "steps": ["Recall buffers need conjugate pairs.", "Eliminate strong-strong, single, salt-only.", "Select option D."], "subject": "chemistry", "text": "Answer: Weak acid plus conjugate base.\nSteps:\n1. Recall buffers need conjugate pairs.\n2. Eliminate strong-strong, single, salt-only.\n3. Select option D.\nAnswer: (D)", "topic": "acids_bases"}
{"answer": "pH je 11, protože pOH = -log(0,001) = 3 a pH = 14 - 3.", "choices": null, "id": "che_0029", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,001 M NaOH.", "steps": ["NaOH disociuje plně: [OH-] = 0,001 M.", "pOH = -log(0,001) = 3.", "pH = 14 - 3 = 11."], "subject": "chemistry", "text": "Answer: 11.\nSteps:\n1. NaOH disociuje plně: [OH-] = 0,001 M.\n2. pOH = -log(0,001) = 3.\n3. pH = 14 - 3 = 11.", "topic": "acids_bases"}
{"answer": "Exactly 25.0 mL of 0.100 M NaOH is needed, matching moles of HCl one to one.", "choices": null, "id": "che_0030", "kind": "worked_example", "lang": "en", "question": "What volume of 0.100 M NaOH neutralizes 25.0 mL of 0.100 M HCl?", "steps": ["Moles HCl = 0.0250 x 0.100 = 0.00250 mol.", "Same moles NaOH needed (1:1).", "V = 0.00250 / 0.100 = 0.0250 L = 25.0 mL."], "subject": "chemistry", "text": "Answer: 25.0 mL.\nSteps:\n1. Moles HCl = 0.0250 x 0.100 = 0.00250 mol.\n2. Same moles NaOH needed (1:1).\n3. V = 0.00250 / 0.100 = 0.0250 L = 25.0 mL.", "topic": "acids_bases"}
{"answer": "A Lewis acid accepts an electron pair while a Lewis base donates one, generalizing beyond protons.", "choices": null, "id": "che_0031", "kind": "concept", "lang": "en", "question": "What is the Lewis definition of acids and bases?", "steps": ["Define Lewis acid as pair acceptor.", "Define Lewis base as pair donor.", "Example: BF3 with NH3."], "subject": "chemistry", "text": "Answer: Acids accept, bases donate electron pairs.\nSteps:\n1. Define Lewis acid as pair acceptor.\n2. Define Lewis base as pair donor.\n3. Example: BF3 with NH3.", "topic": "acids_bases"}
{"answer": "For a conjugate pair Ka times Kb equals Kw, which is 1.0 x 10^-14 at 25 C.", "choices": {"A": "Ka x Kb = Kw", "B": "Ka + Kb = Kw", "C": "Ka / Kb = Kw", "D": "Ka - Kb = Kw"}, "id": "che_0032", "kind": "multiple_choice", "lang": "en", "question": "How are Ka and Kb of a conjugate pair related?", "steps": ["Recall product equals water constant.", "Kw = 1.0 x 10^-14 at 25 C.", "Select option A."], "subject": "chemistry", "text": "Answer: Ka x Kb = Kw.\nSteps:\n1. Recall product equals water constant.\n2. Kw = 1.0 x 10^-14 at 25 C.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "Neutralizace je reakce kyseliny se zásadou za vzniku soli a vody.", "choices": null, "id": "che_0033", "kind": "concept", "lang": "cs", "question": "Co je neutralizace?", "steps": ["Kyselina dodá H+, zásada OH-.", "Vznikne voda a sůl.", "Příklad: HCl + NaOH -> NaCl + H2O."], "subject": "chemistry", "text": "Answer: Kyselina + zásada -> sůl + voda.\nSteps:\n1. Kyselina dodá H+, zásada OH-.\n2. Vznikne voda a sůl.\n3. Příklad: HCl + NaOH -> NaCl + H2O.", "topic": "acids_bases"}
{"answer": "The equivalence point is reached when added titrant stoichiometrically matches the analyte.", "choices": null, "id": "che_0034", "kind": "concept", "lang": "en", "question": "What is the equivalence point of a titration?", "steps": ["Define stoichiometric match.", "Contrast with indicator endpoint.", "Moles titrant = moles analyte x ratio."], "subject": "chemistry", "text": "Answer: Stoichiometric match of titrant and analyte.\nSteps:\n1. Define stoichiometric match.\n2. Contrast with indicator endpoint.\n3. Moles titrant = moles analyte x ratio.", "topic": "acids_bases"}
{"answer": "Phosphoric acid is triprotic with three dissociable protons and three Ka values.", "choices": {"A": "Monoprotic", "B": "Diprotic", "C": "Triprotic", "D": "Aprotic"}, "id": "che_0035", "kind": "multiple_choice", "lang": "en", "question": "How is phosphoric acid (H3PO4) classified?", "steps": ["Count dissociable protons: three.", "Match to triprotic.", "Select option C."], "subject": "chemistry", "text": "Answer: Triprotic.\nSteps:\n1. Count dissociable protons: three.\n2. Match to triprotic.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "Koncentrace H+ je 1 x 10^-5 M, protože 10 na -5 odpovídá pH 5.", "choices": null, "id": "che_0036", "kind": "worked_example", "lang": "cs", "question": "Roztok má pH 5. Vypočítej [H+].", "steps": ["Napiš vzorec: [H+] = 10^(-pH).", "Dosaď: 10^(-5).", "[H+] = 1 x 10^-5 M."], "subject": "chemistry", "text": "Answer: 1 x 10^-5 M.\nSteps:\n1. Napiš vzorec: [H+] = 10^(-pH).\n2. Dosaď: 10^(-5).\n3. [H+] = 1 x 10^-5 M.", "topic": "acids_bases"}
{"answer": "Phenolphthalein stays colorless in acid and turns pink in base around pH 8-10.", "choices": {"A": "Pink in acid, colorless in base", "B": "Blue in acid, yellow in base", "C": "Colorless in acid, pink in base", "D": "Red in acid, blue in base"}, "id": "che_0037", "kind": "multiple_choice", "lang": "en", "question": "How does phenolphthalein change color?", "steps": ["Recall acid form is colorless.", "Base form is pink above pH 8.", "Select option C."], "subject": "chemistry", "text": "Answer: Colorless in acid, pink in base.\nSteps:\n1. Recall acid form is colorless.\n2. Base form is pink above pH 8.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "The pH is 2.87, from [H+] = sqrt(1.8 x 10^-5 x 0.10) = 1.34 x 10^-3 M.", "choices": null, "id": "che_0038", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.10 M acetic acid (Ka = 1.8 x 10^-5).", "steps": ["Approximate: [H+] = sqrt(Ka x C).", "Substitute: sqrt(1.8 x 10^-6) = 1.34 x 10^-3.", "pH = -log(1.34 x 10^-3) = 2.87."], "subject": "chemistry", "text": "Answer: 2.87.\nSteps:\n1. Approximate: [H+] = sqrt(Ka x C).\n2. Substitute: sqrt(1.8 x 10^-6) = 1.34 x 10^-3.\n3. pH = -log(1.34 x 10^-3) = 2.87.", "topic": "acids_bases"}
{"answer": "Oxidation is loss of electrons and reduction is gain, remembered as OILRIG.", "choices": null, "id": "che_0039", "kind": "concept", "lang": "en", "question": "What are oxidation and reduction?", "steps": ["Oxidation: lose electrons.", "Reduction: gain electrons.", "They always occur together."], "subject": "chemistry", "text": "Answer: Loss versus gain of electrons.\nSteps:\n1. Oxidation: lose electrons.\n2. Reduction: gain electrons.\n3. They always occur together.", "topic": "redox"}
{"answer": "Oxidace je ztráta elektronů a redukce jejich zisk; probíhají vždy současně.", "choices": null, "id": "che_0040", "kind": "concept", "lang": "cs", "question": "Co je oxidace a redukce?", "steps": ["Oxidace: odevzdání elektronů.", "Redukce: přijetí elektronů.", "Příklad: Zn + Cu2+ -> Zn2+ + Cu."], "subject": "chemistry", "text": "Answer: Ztráta versus zisk elektronů.\nSteps:\n1. Oxidace: odevzdání elektronů.\n2. Redukce: přijetí elektronů.\n3. Příklad: Zn + Cu2+ -> Zn2+ + Cu.", "topic": "redox"}
{"answer": "Sulfur has oxidation state +6, since 2(+1) + S + 4(-2) = 0 gives S = +6.", "choices": {"A": "-2", "B": "0", "C": "+4", "D": "+6"}, "id": "che_0041", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of sulfur in H2SO4?", "steps": ["Assign H +1 and O -2.", "Solve: 2 + S - 8 = 0.", "S = +6; select D."], "subject": "chemistry", "text": "Answer: +6.\nSteps:\n1. Assign H +1 and O -2.\n2. Solve: 2 + S - 8 = 0.\n3. S = +6; select D.\nAnswer: (D)", "topic": "redox"}
{"answer": "Manganese is +7, since +1 + Mn + 4(-2) = 0 gives Mn = +7.", "choices": null, "id": "che_0042", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of Mn in KMnO4.", "steps": ["Assign K +1 and O -2.", "Equation: 1 + Mn - 8 = 0.", "Mn = +7."], "subject": "chemistry", "text": "Answer: +7.\nSteps:\n1. Assign K +1 and O -2.\n2. Equation: 1 + Mn - 8 = 0.\n3. Mn = +7.", "topic": "redox"}
{"answer": "The oxidizing agent is reduced while the reducing agent is oxidized in the reaction.", "choices": null, "id": "che_0043", "kind": "concept", "lang": "en", "question": "How do oxidizing and reducing agents change?", "steps": ["Oxidizing agent gains electrons.", "Reducing agent loses electrons.", "Example: Cu2+ oxidizes Zn."], "subject": "chemistry", "text": "Answer: Oxidizer is reduced; reducer is oxidized.\nSteps:\n1. Oxidizing agent gains electrons.\n2. Reducing agent loses electrons.\n3. Example: Cu2+ oxidizes Zn.", "topic": "redox"}
{"answer": "The reduced species gains electrons, so its oxidation number decreases.", "choices": {"A": "Loses electrons", "B": "Gains electrons", "C": "Loses protons", "D": "Gains protons"}, "id": "che_0044", "kind": "multiple_choice", "lang": "en", "question": "What happens to the species being reduced?", "steps": ["Recall reduction means gain.", "Electrons are gained.", "Select option B."], "subject": "chemistry", "text": "Answer: Gains electrons.\nSteps:\n1. Recall reduction means gain.\n2. Electrons are gained.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "The balanced equation is 4Fe + 3O2 -> 2Fe2O3.", "choices": null, "id": "che_0045", "kind": "worked_example", "lang": "en", "question": "Balance: Fe + O2 -> Fe2O3.", "steps": ["Balance Fe with 2 Fe2O3 and 4 Fe.", "Count O: 6 atoms each side.", "Use 3 O2: 4Fe + 3O2 -> 2Fe2O3."], "subject": "chemistry", "text": "Answer: 4Fe + 3O2 -> 2Fe2O3.\nSteps:\n1. Balance Fe with 2 Fe2O3 and 4 Fe.\n2. Count O: 6 atoms each side.\n3. Use 3 O2: 4Fe + 3O2 -> 2Fe2O3.", "topic": "redox"}
{"answer": "Chrom má oxidační číslo +6, protože 2 + 2Cr - 14 = 0 dává Cr = +6.", "choices": null, "id": "che_0046", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo chromu v K2Cr2O7.", "steps": ["Přiřaď K +1 a O -2.", "Rovnice: 2 + 2Cr - 14 = 0.", "Cr = +6."], "subject": "chemistry", "text": "Answer: +6.\nSteps:\n1. Přiřaď K +1 a O -2.\n2. Rovnice: 2 + 2Cr - 14 = 0.\n3. Cr = +6.", "topic": "redox"}
{"answer": "Zinc dissolves in acid because it sits above hydrogen in the activity series, unlike copper or silver.", "choices": {"A": "Cu", "B": "Ag", "C": "Zn", "D": "Au"}, "id": "che_0047", "kind": "multiple_choice", "lang": "en", "question": "Which metal is oxidized by H+ from dilute acid?", "steps": ["Recall only metals above H react.", "Eliminate Cu, Ag, Au.", "Select option C."], "subject": "chemistry", "text": "Answer: Zn.\nSteps:\n1. Recall only metals above H react.\n2. Eliminate Cu, Ag, Au.\n3. Select option C.\nAnswer: (C)", "topic": "redox"}
{"answer": "The activity series ranks metals by ease of oxidation, predicting single-replacement outcomes.", "choices": null, "id": "che_0048", "kind": "concept", "lang": "en", "question": "What is the metal activity series?", "steps": ["Rank by tendency to oxidize.", "Higher metals displace lower ions.", "Example: Zn displaces Cu2+."], "subject": "chemistry", "text": "Answer: Ranking of metals by reactivity.\nSteps:\n1. Rank by tendency to oxidize.\n2. Higher metals displace lower ions.\n3. Example: Zn displaces Cu2+.", "topic": "redox"}
{"answer": "Four electrons transfer: each Mg loses 2 and the O2 molecule gains 4 total.", "choices": null, "id": "che_0049", "kind": "worked_example", "lang": "en", "question": "How many electrons transfer in 2Mg + O2 -> 2MgO?", "steps": ["Each Mg: 0 -> +2, loses 2.", "Two Mg lose 4 total.", "O2 gains 4; transfer = 4 e-."], "subject": "chemistry", "text": "Answer: 4 electrons.\nSteps:\n1. Each Mg: 0 -> +2, loses 2.\n2. Two Mg lose 4 total.\n3. O2 gains 4; transfer = 4 e-.", "topic": "redox"}
{"answer": "Chlorine is both oxidized and reduced in Cl2 + H2O -> Cl- + ClO- + 2H+, a disproportionation.", "choices": {"A": "Cl2 -> Cl- plus ClO-", "B": "Zn + Cu2+ -> Zn2+ + Cu", "C": "HCl + NaOH -> NaCl + H2O", "D": "Ag+ + Cl- -> AgCl"}, "id": "che_0050", "kind": "multiple_choice", "lang": "en", "question": "Which reaction is a disproportionation?", "steps": ["Need one element both oxidized and reduced.", "Only chlorine qualifies.", "Select option A."], "subject": "chemistry", "text": "Answer: Cl2 -> Cl- plus ClO-.\nSteps:\n1. Need one element both oxidized and reduced.\n2. Only chlorine qualifies.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Balance atoms first, then add H+, H2O, and electrons to balance charge in acidic solution.", "choices": null, "id": "che_0051", "kind": "concept", "lang": "en", "question": "How is redox balanced in acidic solution?", "steps": ["Split into half-reactions.", "Balance atoms with H2O and H+.", "Balance charge with electrons."], "subject": "chemistry", "text": "Answer: Half-reactions with H+, H2O, electrons.\nSteps:\n1. Split into half-reactions.\n2. Balance atoms with H2O and H+.\n3. Balance charge with electrons.", "topic": "redox"}
{"answer": "Redoxní reakce je přenos elektronů mezi oxidovadlem a redukovadlem.", "choices": null, "id": "che_0052", "kind": "concept", "lang": "cs", "question": "Co je redoxní reakce?", "steps": ["Definuj přenos elektronů.", "Oxidovadlo se redukuje.", "Redukovadlo se oxiduje."], "subject": "chemistry", "text": "Answer: Přenos elektronů.\nSteps:\n1. Definuj přenos elektronů.\n2. Oxidovadlo se redukuje.\n3. Redukovadlo se oxiduje.", "topic": "redox"}
{"answer": "Carbon is -4 in methane, since C + 4(+1) = 0 gives C = -4.", "choices": {"A": "-4", "B": "0", "C": "+2", "D": "+4"}, "id": "che_0053", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of carbon in CH4?", "steps": ["Assign H +1.", "Solve: C + 4 = 0.", "C = -4; select A."], "subject": "chemistry", "text": "Answer: -4.\nSteps:\n1. Assign H +1.\n2. Solve: C + 4 = 0.\n3. C = -4; select A.\nAnswer: (A)", "topic": "redox"}
{"answer": "The balanced half-reaction is MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O.", "choices": null, "id": "che_0054", "kind": "worked_example", "lang": "en", "question": "Balance the half-reaction MnO4- -> Mn2+ in acid.", "steps": ["Balance O with 4 H2O.", "Balance H with 8 H+.", "Balance charge: left +7, add 5 e-."], "subject": "chemistry", "text": "Answer: MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O.\nSteps:\n1. Balance O with 4 H2O.\n2. Balance H with 8 H+.\n3. Balance charge: left +7, add 5 e-.", "topic": "redox"}
{"answer": "Spectator ions appear unchanged on both sides and are omitted from the net ionic equation.", "choices": null, "id": "che_0055", "kind": "concept", "lang": "en", "question": "What are spectator ions?", "steps": ["Identify ions unchanged by reaction.", "Example: Na+ in precipitation.", "Cancel them for net equation."], "subject": "chemistry", "text": "Answer: Ions unchanged, omitted from net equation.\nSteps:\n1. Identify ions unchanged by reaction.\n2. Example: Na+ in precipitation.\n3. Cancel them for net equation.", "topic": "redox"}
{"answer": "Aluminum is the reducing agent because it loses electrons going from 0 to +3.", "choices": {"A": "Fe2O3", "B": "Al", "C": "Fe", "D": "Al2O3"}, "id": "che_0056", "kind": "multiple_choice", "lang": "en", "question": "In 2Al + Fe2O3 -> Al2O3 + 2Fe, what is the reducing agent?", "steps": ["Find species oxidized: Al 0 -> +3.", "Reducer is the oxidized species.", "Select option B."], "subject": "chemistry", "text": "Answer: Al.\nSteps:\n1. Find species oxidized: Al 0 -> +3.\n2. Reducer is the oxidized species.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "Vyčíslená rovnice je 2H2 + O2 -> 2H2O.", "choices": null, "id": "che_0057", "kind": "worked_example", "lang": "cs", "question": "Vyčísli: H2 + O2 -> H2O.", "steps": ["Vodík: 2 H2O a 2 H2.", "Kyslík: 1 O2 na 2 O.", "Výsledek: 2H2 + O2 -> 2H2O."], "subject": "chemistry", "text": "Answer: 2H2 + O2 -> 2H2O.\nSteps:\n1. Vodík: 2 H2O a 2 H2.\n2. Kyslík: 1 O2 na 2 O.\n3. Výsledek: 2H2 + O2 -> 2H2O.", "topic": "redox"}
{"answer": "Exothermic reactions release heat with negative ΔH, while endothermic reactions absorb heat with positive ΔH.", "choices": null, "id": "che_0058", "kind": "concept", "lang": "en", "question": "How do exothermic and endothermic reactions differ?", "steps": ["Exothermic: heat out, ΔH negative.", "Endothermic: heat in, ΔH positive.", "Example: combustion versus ice melting."], "subject": "chemistry", "text": "Answer: Heat released versus absorbed.\nSteps:\n1. Exothermic: heat out, ΔH negative.\n2. Endothermic: heat in, ΔH positive.\n3. Example: combustion versus ice melting.", "topic": "thermochemistry"}
{"answer": "An exothermic reaction has negative ΔH because the system loses heat to the surroundings.", "choices": {"A": "Positive ΔH", "B": "Negative ΔH", "C": "Zero ΔH", "D": "Infinite ΔH"}, "id": "che_0059", "kind": "multiple_choice", "lang": "en", "question": "What is the sign of ΔH for an exothermic reaction?", "steps": ["Recall exo means heat exits.", "Enthalpy of system drops.", "Select option B."], "subject": "chemistry", "text": "Answer: Negative ΔH.\nSteps:\n1. Recall exo means heat exits.\n2. Enthalpy of system drops.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "Entalpie je tepelný obsah soustavy; její změna ΔH udává teplo reakce při stálém tlaku.", "choices": null, "id": "che_0060", "kind": "concept", "lang": "cs", "question": "Co je entalpie?", "steps": ["Definuj tepelný obsah soustavy.", "ΔH je teplo při stálém tlaku.", "Záporná = exotermická."], "subject": "chemistry", "text": "Answer: Tepelný obsah soustavy.\nSteps:\n1. Definuj tepelný obsah soustavy.\n2. ΔH je teplo při stálém tlaku.\n3. Záporná = exotermická.", "topic": "thermochemistry"}
{"answer": "The heat required is 50.2 kJ, from 200 g x 4.184 J/gC x 60 C.", "choices": null, "id": "che_0061", "kind": "worked_example", "lang": "en", "question": "How much heat warms 200 g of water from 20 C to 80 C (c = 4.184 J/gC)?", "steps": ["Write: q = m x c x ΔT.", "Substitute: 200 x 4.184 x 60.", "q = 50,208 J = 50.2 kJ."], "subject": "chemistry", "text": "Answer: 50.2 kJ.\nSteps:\n1. Write: q = m x c x ΔT.\n2. Substitute: 200 x 4.184 x 60.\n3. q = 50,208 J = 50.2 kJ.", "topic": "thermochemistry"}
{"answer": "Liquid water has a specific heat of 4.184 J/gC, unusually high due to hydrogen bonding.", "choices": {"A": "1.00 J/gC", "B": "2.05 J/gC", "C": "4.184 J/gC", "D": "8.314 J/gC"}, "id": "che_0062", "kind": "multiple_choice", "lang": "en", "question": "What is the specific heat capacity of liquid water?", "steps": ["Recall 4.184 J/gC.", "Eliminate other values.", "Select option C."], "subject": "chemistry", "text": "Answer: 4.184 J/gC.\nSteps:\n1. Recall 4.184 J/gC.\n2. Eliminate other values.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "Hess's law states the total enthalpy change is the sum of step changes, independent of path.", "choices": null, "id": "che_0063", "kind": "concept", "lang": "en", "question": "What is Hess's law?", "steps": ["Enthalpy is a state function.", "Sum ΔH of steps.", "Path independence holds."], "subject": "chemistry", "text": "Answer: Total ΔH equals sum of steps.\nSteps:\n1. Enthalpy is a state function.\n2. Sum ΔH of steps.\n3. Path independence holds.", "topic": "thermochemistry"}
{"answer": "The overall ΔH is -15 kJ, from +10 plus -25 kJ.", "choices": null, "id": "che_0064", "kind": "worked_example", "lang": "en", "question": "A->B has ΔH = +10 kJ and B->C has ΔH = -25 kJ. Find ΔH for A->C.", "steps": ["Apply Hess's law: sum steps.", "Add: 10 + (-25).", "ΔH = -15 kJ."], "subject": "chemistry", "text": "Answer: -15 kJ.\nSteps:\n1. Apply Hess's law: sum steps.\n2. Add: 10 + (-25).\n3. ΔH = -15 kJ.", "topic": "thermochemistry"}
{"answer": "Standard enthalpy of formation uses 1 bar pressure and 298 K with elements in reference states.", "choices": {"A": "1 bar and 298 K", "B": "0 bar and 0 K", "C": "10 bar and 500 K", "D": "STP only"}, "id": "che_0065", "kind": "multiple_choice", "lang": "en", "question": "What are standard conditions for ΔHf?", "steps": ["Recall 1 bar pressure.", "Recall 298 K temperature.", "Select option A."], "subject": "chemistry", "text": "Answer: 1 bar and 298 K.\nSteps:\n1. Recall 1 bar pressure.\n2. Recall 298 K temperature.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "Potřebné teplo je 4184 J, protože 100 x 4,184 x 10 se rovná 4184.", "choices": null, "id": "che_0066", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla ohřeje 100 g vody o 10 °C (c = 4,184 J/g°C)?", "steps": ["Napiš vzorec: q = m x c x ΔT.", "Dosaď: 100 x 4,184 x 10.", "q = 4184 J."], "subject": "chemistry", "text": "Answer: 4184 J.\nSteps:\n1. Napiš vzorec: q = m x c x ΔT.\n2. Dosaď: 100 x 4,184 x 10.\n3. q = 4184 J.", "topic": "thermochemistry"}
{"answer": "Reaction ΔH is estimated as bonds broken minus bonds formed, since breaking costs and forming releases energy.", "choices": null, "id": "che_0067", "kind": "concept", "lang": "en", "question": "How do bond energies estimate reaction enthalpy?", "steps": ["Sum energy of bonds broken.", "Subtract energy of bonds formed.", "Positive means endothermic."], "subject": "chemistry", "text": "Answer: Broken minus formed.\nSteps:\n1. Sum energy of bonds broken.\n2. Subtract energy of bonds formed.\n3. Positive means endothermic.", "topic": "thermochemistry"}
{"answer": "The ΔH is -184 kJ, from 678 kJ broken minus 862 kJ formed.", "choices": null, "id": "che_0068", "kind": "worked_example", "lang": "en", "question": "Estimate ΔH for H2 + Cl2 -> 2HCl using H-H 436, Cl-Cl 242, H-Cl 431 kJ/mol.", "steps": ["Broken: 436 + 242 = 678 kJ.", "Formed: 2 x 431 = 862 kJ.", "ΔH = 678 - 862 = -184 kJ."], "subject": "chemistry", "text": "Answer: -184 kJ.\nSteps:\n1. Broken: 436 + 242 = 678 kJ.\n2. Formed: 2 x 431 = 862 kJ.\n3. ΔH = 678 - 862 = -184 kJ.", "topic": "thermochemistry"}
{"answer": "Entropy rises when a solid vaporizes because gas particles have far more disorder.", "choices": {"A": "Gas condenses", "B": "Liquid freezes", "C": "Gas dissolves", "D": "Solid vaporizes"}, "id": "che_0069", "kind": "multiple_choice", "lang": "en", "question": "In which change does entropy increase most?", "steps": ["Recall gas has highest entropy.", "Only vaporization creates gas.", "Select option D."], "subject": "chemistry", "text": "Answer: Solid vaporizes.\nSteps:\n1. Recall gas has highest entropy.\n2. Only vaporization creates gas.\n3. Select option D.\nAnswer: (D)", "topic": "thermochemistry"}
{"answer": "Exotermická reakce uvolňuje teplo do okolí a má zápornou změnu entalpie.", "choices": null, "id": "che_0070", "kind": "concept", "lang": "cs", "question": "Co je exotermická reakce?", "steps": ["Definuj uvolnění tepla.", "ΔH je záporné.", "Příklad: hoření metanu."], "subject": "chemistry", "text": "Answer: Reakce uvolňující teplo.\nSteps:\n1. Definuj uvolnění tepla.\n2. ΔH je záporné.\n3. Příklad: hoření metanu.", "topic": "thermochemistry"}
{"answer": "ΔG is -40.4 kJ, so the reaction is spontaneous at 298 K.", "choices": null, "id": "che_0071", "kind": "worked_example", "lang": "en", "question": "Given ΔH = -100 kJ and ΔS = -0.200 kJ/K at 298 K, compute ΔG.", "steps": ["Write: ΔG = ΔH - TΔS.", "Substitute: -100 - 298 x (-0.200) = -100 + 59.6.", "ΔG = -40.4 kJ, spontaneous."], "subject": "chemistry", "text": "Answer: -40.4 kJ.\nSteps:\n1. Write: ΔG = ΔH - TΔS.\n2. Substitute: -100 - 298 x (-0.200) = -100 + 59.6.\n3. ΔG = -40.4 kJ, spontaneous.", "topic": "thermochemistry"}
{"answer": "A negative Gibbs free energy change means the process is spontaneous under the given conditions.", "choices": {"A": "Positive ΔG", "B": "Negative ΔG", "C": "Zero ΔG always", "D": "ΔG is irrelevant"}, "id": "che_0072", "kind": "multiple_choice", "lang": "en", "question": "What ΔG sign indicates a spontaneous process?", "steps": ["Recall spontaneity needs ΔG < 0.", "Eliminate positive, zero, irrelevant.", "Select option B."], "subject": "chemistry", "text": "Answer: Negative ΔG.\nSteps:\n1. Recall spontaneity needs ΔG < 0.\n2. Eliminate positive, zero, irrelevant.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "Calorimetry measures heat flow from temperature change in an insulated vessel of known heat capacity.", "choices": null, "id": "che_0073", "kind": "concept", "lang": "en", "question": "What is calorimetry?", "steps": ["Run reaction in insulated vessel.", "Measure temperature change.", "Compute q from mass and heat capacity."], "subject": "chemistry", "text": "Answer: Measuring heat via temperature change.\nSteps:\n1. Run reaction in insulated vessel.\n2. Measure temperature change.\n3. Compute q from mass and heat capacity.", "topic": "thermochemistry"}
{"answer": "Hessův zákon říká, že celková změna entalpie je součtem změn dílčích kroků.", "choices": null, "id": "che_0074", "kind": "concept", "lang": "cs", "question": "Co je Hessův zákon?", "steps": ["Entalpie je stavová funkce.", "Sečti ΔH kroků.", "Cesta nehraje roli."], "subject": "chemistry", "text": "Answer: Celkové ΔH je součet kroků.\nSteps:\n1. Entalpie je stavová funkce.\n2. Sečti ΔH kroků.\n3. Cesta nehraje roli.", "topic": "thermochemistry"}
{"answer": "A spontaneous process increases the entropy of the universe, per the second law.", "choices": {"A": "ΔS universe < 0", "B": "ΔS universe = 0", "C": "ΔS universe > 0", "D": "ΔS universe is undefined"}, "id": "che_0075", "kind": "multiple_choice", "lang": "en", "question": "What is ΔS of the universe for a spontaneous process?", "steps": ["Recall second law of thermodynamics.", "Spontaneous means universe entropy rises.", "Select option C."], "subject": "chemistry", "text": "Answer: ΔS universe > 0.\nSteps:\n1. Recall second law of thermodynamics.\n2. Spontaneous means universe entropy rises.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "Burning 32.0 g of methane releases 1780 kJ, from 2.00 mol times 890 kJ/mol.", "choices": null, "id": "che_0076", "kind": "worked_example", "lang": "en", "question": "Methane's heat of combustion is 890 kJ/mol. How much heat from 32.0 g (M = 16.04 g/mol)?", "steps": ["Moles = 32.0 / 16.04 = 2.00 mol.", "Multiply: 2.00 x 890.", "Heat = 1780 kJ released."], "subject": "chemistry", "text": "Answer: 1780 kJ.\nSteps:\n1. Moles = 32.0 / 16.04 = 2.00 mol.\n2. Multiply: 2.00 x 890.\n3. Heat = 1780 kJ released.", "topic": "thermochemistry"}
{"answer": "Alkanes are named by longest carbon chain with the -ane suffix: methane, ethane, propane, butane.", "choices": null, "id": "che_0077", "kind": "concept", "lang": "en", "question": "How are simple alkanes named?", "steps": ["Find the longest carbon chain.", "Use the -ane suffix.", "Count: 1 methane, 2 ethane, 3 propane."], "subject": "chemistry", "text": "Answer: Longest chain plus -ane.\nSteps:\n1. Find the longest carbon chain.\n2. Use the -ane suffix.\n3. Count: 1 methane, 2 ethane, 3 propane.", "topic": "organic_naming"}
{"answer": "A four-carbon straight chain is butane.", "choices": {"A": "Propane", "B": "Butane", "C": "Pentane", "D": "Ethene"}, "id": "che_0078", "kind": "multiple_choice", "lang": "en", "question": "What is the name of CH3CH2CH2CH3?", "steps": ["Count carbons: four.", "Single bonds mean alkane.", "Select option B."], "subject": "chemistry", "text": "Answer: Butane.\nSteps:\n1. Count carbons: four.\n2. Single bonds mean alkane.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "Alkany se pojmenují podle nejdelšího řetězce koncovkou -an: methan, ethan, propan, butan.", "choices": null, "id": "che_0079", "kind": "concept", "lang": "cs", "question": "Jak se pojmenovávají alkany?", "steps": ["Najdi nejdelší řetězec.", "Přidej koncovku -an.", "Počítej: 1 methan, 2 ethan."], "subject": "chemistry", "text": "Answer: Řetězec plus -an.\nSteps:\n1. Najdi nejdelší řetězec.\n2. Přidej koncovku -an.\n3. Počítej: 1 methan, 2 ethan.", "topic": "organic_naming"}
{"answer": "The name is 2-methylpropane: a three-carbon chain with a methyl branch on carbon 2.", "choices": null, "id": "che_0080", "kind": "worked_example", "lang": "en", "question": "Name CH3CH(CH3)CH3.", "steps": ["Longest chain: 3 carbons = propane.", "Methyl branch on carbon 2.", "Name: 2-methylpropane."], "subject": "chemistry", "text": "Answer: 2-methylpropane.\nSteps:\n1. Longest chain: 3 carbons = propane.\n2. Methyl branch on carbon 2.\n3. Name: 2-methylpropane.", "topic": "organic_naming"}
{"answer": "The -OH group marks an alcohol, named with the -ol suffix.", "choices": {"A": "Alcohol", "B": "Ketone", "C": "Ether", "D": "Ester"}, "id": "che_0081", "kind": "multiple_choice", "lang": "en", "question": "Which functional group contains -OH on carbon?", "steps": ["Recall -OH means alcohol.", "Eliminate ketone, ether, ester.", "Select option A."], "subject": "chemistry", "text": "Answer: Alcohol.\nSteps:\n1. Recall -OH means alcohol.\n2. Eliminate ketone, ether, ester.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "Alkenes use the -ene suffix for double bonds and alkynes use -yne for triple bonds.", "choices": null, "id": "che_0082", "kind": "concept", "lang": "en", "question": "How do alkene and alkyne names differ?", "steps": ["Double bond gives -ene.", "Triple bond gives -yne.", "Example: ethene versus ethyne."], "subject": "chemistry", "text": "Answer: -ene for double, -yne for triple.\nSteps:\n1. Double bond gives -ene.\n2. Triple bond gives -yne.\n3. Example: ethene versus ethyne.", "topic": "organic_naming"}
{"answer": "The name is propene: three carbons with a double bond starting at carbon 1.", "choices": null, "id": "che_0083", "kind": "worked_example", "lang": "en", "question": "Name CH2=CHCH3.", "steps": ["Count 3 carbons.", "Double bond gives -ene.", "Name: propene."], "subject": "chemistry", "text": "Answer: Propene.\nSteps:\n1. Count 3 carbons.\n2. Double bond gives -ene.\n3. Name: propene.", "topic": "organic_naming"}
{"answer": "CH3COOH je kyselina ethanová, běžně zvaná kyselina octová.", "choices": null, "id": "che_0084", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH3COOH.", "steps": ["Skupina -COOH je karboxylová kyselina.", "Dva uhlíky = ethanová.", "Triviálně kyselina octová."], "subject": "chemistry", "text": "Answer: Kyselina ethanová (octová).\nSteps:\n1. Skupina -COOH je karboxylová kyselina.\n2. Dva uhlíky = ethanová.\n3. Triviálně kyselina octová.", "topic": "organic_naming"}
{"answer": "Benzene is aromatic with a delocalized six-electron ring, unlike the non-aromatic choices.", "choices": {"A": "Cyclohexane", "B": "Hexene", "C": "Ethanol", "D": "Benzene"}, "id": "che_0085", "kind": "multiple_choice", "lang": "en", "question": "Which compound is aromatic?", "steps": ["Recall aromatic means benzene-like ring.", "Eliminate cyclohexane, hexene, ethanol.", "Select option D."], "subject": "chemistry", "text": "Answer: Benzene.\nSteps:\n1. Recall aromatic means benzene-like ring.\n2. Eliminate cyclohexane, hexene, ethanol.\n3. Select option D.\nAnswer: (D)", "topic": "organic_naming"}
{"answer": "Methyl is -CH3 and ethyl is -CH2CH3, named as substituents with position numbers.", "choices": null, "id": "che_0086", "kind": "concept", "lang": "en", "question": "What are methyl and ethyl substituents?", "steps": ["Methyl = one-carbon branch.", "Ethyl = two-carbon branch.", "Number their positions on the chain."], "subject": "chemistry", "text": "Answer: One- and two-carbon branches.\nSteps:\n1. Methyl = one-carbon branch.\n2. Ethyl = two-carbon branch.\n3. Number their positions on the chain.", "topic": "organic_naming"}
{"answer": "The name is ethanol: two carbons with an -OH group.", "choices": null, "id": "che_0087", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2OH.", "steps": ["Count 2 carbons.", "-OH gives -ol suffix.", "Name: ethanol."], "subject": "chemistry", "text": "Answer: Ethanol.\nSteps:\n1. Count 2 carbons.\n2. -OH gives -ol suffix.\n3. Name: ethanol.", "topic": "organic_naming"}
{"answer": "The -COOH group defines a carboxylic acid.", "choices": {"A": "Alcohol", "B": "Aldehyde", "C": "Carboxylic acid", "D": "Amine"}, "id": "che_0088", "kind": "multiple_choice", "lang": "en", "question": "Which functional group is -COOH?", "steps": ["Recall C(=O)OH is carboxyl.", "Eliminate alcohol, aldehyde, amine.", "Select option C."], "subject": "chemistry", "text": "Answer: Carboxylic acid.\nSteps:\n1. Recall C(=O)OH is carboxyl.\n2. Eliminate alcohol, aldehyde, amine.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "Structural isomers share a molecular formula but differ in atom connectivity.", "choices": null, "id": "che_0089", "kind": "concept", "lang": "en", "question": "What are structural isomers?", "steps": ["Same formula, different connections.", "Example: butane vs methylpropane.", "Properties differ."], "subject": "chemistry", "text": "Answer: Same formula, different connectivity.\nSteps:\n1. Same formula, different connections.\n2. Example: butane vs methylpropane.\n3. Properties differ.", "topic": "organic_naming"}
{"answer": "Izomery mají stejný vzorec, ale různé uspořádání atomů.", "choices": null, "id": "che_0090", "kind": "concept", "lang": "cs", "question": "Co jsou izomery?", "steps": ["Stejný molekulový vzorec.", "Různé uspořádání.", "Příklad: butan a methylpropan."], "subject": "chemistry", "text": "Answer: Stejný vzorec, jiné uspořádání.\nSteps:\n1. Stejný molekulový vzorec.\n2. Různé uspořádání.\n3. Příklad: butan a methylpropan.", "topic": "organic_naming"}
{"answer": "The name is butan-2-ol: four carbons with -OH on carbon 2.", "choices": null, "id": "che_0091", "kind": "worked_example", "lang": "en", "question": "Name CH3CH(OH)CH2CH3.", "steps": ["Longest chain: 4 = butane.", "-OH on carbon 2.", "Name: butan-2-ol."], "subject": "chemistry", "text": "Answer: Butan-2-ol.\nSteps:\n1. Longest chain: 4 = butane.\n2. -OH on carbon 2.\n3. Name: butan-2-ol.", "topic": "organic_naming"}
{"answer": "A mid-chain C=O is a ketone, while a terminal C=O with H is an aldehyde.", "choices": {"A": "Aldehyde", "B": "Ketone", "C": "Acid", "D": "Ester"}, "id": "che_0092", "kind": "multiple_choice", "lang": "en", "question": "A carbonyl in the middle of a chain is what?", "steps": ["Mid-chain C=O means ketone.", "Eliminate aldehyde, acid, ester.", "Select option B."], "subject": "chemistry", "text": "Answer: Ketone.\nSteps:\n1. Mid-chain C=O means ketone.\n2. Eliminate aldehyde, acid, ester.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "Esters combine an acid part and an alcohol part, named as alkyl alkanoate.", "choices": null, "id": "che_0093", "kind": "concept", "lang": "en", "question": "How are esters named?", "steps": ["Alcohol part gives alkyl prefix.", "Acid part gives alkanoate.", "Example: methyl ethanoate."], "subject": "chemistry", "text": "Answer: Alkyl alkanoate.\nSteps:\n1. Alcohol part gives alkyl prefix.\n2. Acid part gives alkanoate.\n3. Example: methyl ethanoate.", "topic": "organic_naming"}
{"answer": "CH3COCH3 je propanon, triviálně aceton.", "choices": null, "id": "che_0094", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH3COCH3.", "steps": ["Karbonyl uprostřed = keton.", "Tři uhlíky = propanon.", "Triviálně aceton."], "subject": "chemistry", "text": "Answer: Propanon (aceton).\nSteps:\n1. Karbonyl uprostřed = keton.\n2. Tři uhlíky = propanon.\n3. Triviálně aceton.", "topic": "organic_naming"}
{"answer": "Carboxylic acids outrank aldehydes, ketones, alcohols, and amines for the suffix.", "choices": null, "id": "che_0095", "kind": "concept", "lang": "en", "question": "Which functional group has naming priority?", "steps": ["Carboxylic acid is highest.", "Then aldehyde, ketone, alcohol.", "Highest group sets the suffix."], "subject": "chemistry", "text": "Answer: Carboxylic acid.\nSteps:\n1. Carboxylic acid is highest.\n2. Then aldehyde, ketone, alcohol.\n3. Highest group sets the suffix.", "topic": "organic_naming"}
{"answer": "Nucleophiles donate electron pairs to electron-poor electrophiles.", "choices": null, "id": "che_0096", "kind": "concept", "lang": "en", "question": "What are nucleophiles and electrophiles?", "steps": ["Nucleophile: electron-rich donor.", "Electrophile: electron-poor acceptor.", "They attract each other."], "subject": "chemistry", "text": "Answer: Pair donors versus acceptors.\nSteps:\n1. Nucleophile: electron-rich donor.\n2. Electrophile: electron-poor acceptor.\n3. They attract each other.", "topic": "organic_mechanisms"}
{"answer": "Hydroxide is a nucleophile with lone pairs ready to donate.", "choices": {"A": "OH(-)", "B": "H(+)", "C": "BF3", "D": "Carbocation"}, "id": "che_0097", "kind": "multiple_choice", "lang": "en", "question": "Which species is a nucleophile?", "steps": ["Need electron-rich donor.", "Eliminate H+, BF3, carbocation.", "Select option A."], "subject": "chemistry", "text": "Answer: OH-.\nSteps:\n1. Need electron-rich donor.\n2. Eliminate H+, BF3, carbocation.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "SN1 is two-step via a carbocation with rate depending on substrate only, while SN2 is one-step with both reactants in the rate.", "choices": null, "id": "che_0098", "kind": "concept", "lang": "en", "question": "How do SN1 and SN2 reactions differ?", "steps": ["SN1: carbocation, rate = k[RX].", "SN2: concerted, rate = k[RX][Nu].", "SN1 favors tertiary, SN2 methyl."], "subject": "chemistry", "text": "Answer: Two-step versus one-step substitution.\nSteps:\n1. SN1: carbocation, rate = k[RX].\n2. SN2: concerted, rate = k[RX][Nu].\n3. SN1 favors tertiary, SN2 methyl.", "topic": "organic_mechanisms"}
{"answer": "Nukleofil je částice bohatá na elektrony, která je donuje elektrofilu.", "choices": null, "id": "che_0099", "kind": "concept", "lang": "cs", "question": "Co je nukleofil?", "steps": ["Bohatý na elektrony.", "Napadá elektrofil.", "Příklad: OH-, CN-."], "subject": "chemistry", "text": "Answer: Donor elektronového páru.\nSteps:\n1. Bohatý na elektrony.\n2. Napadá elektrofil.\n3. Příklad: OH-, CN-.", "topic": "organic_mechanisms"}
{"answer": "The SN1 rate doubles to 2x because rate depends only on substrate concentration.", "choices": null, "id": "che_0100", "kind": "worked_example", "lang": "en", "question": "In an SN1 reaction with rate = k[RX], what happens to the rate if [RX] doubles?", "steps": ["Write: rate = k[RX].", "Double [RX]: rate = k x 2[RX].", "Rate doubles to 2x."], "subject": "chemistry", "text": "Answer: Rate doubles.\nSteps:\n1. Write: rate = k[RX].\n2. Double [RX]: rate = k x 2[RX].\n3. Rate doubles to 2x.", "topic": "organic_mechanisms"}
{"answer": "Tertiary halides form the most stable carbocations, so they react fastest by SN1.", "choices": {"A": "Methyl", "B": "Primary", "C": "Tertiary", "D": "Aryl"}, "id": "che_0101", "kind": "multiple_choice", "lang": "en", "question": "Which substrate reacts fastest by SN1?", "steps": ["SN1 needs stable carbocation.", "Tertiary is most stable.", "Select option C."], "subject": "chemistry", "text": "Answer: Tertiary.\nSteps:\n1. SN1 needs stable carbocation.\n2. Tertiary is most stable.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "Carbocation stability rises with substitution: tertiary beats secondary beats primary beats methyl.", "choices": null, "id": "che_0102", "kind": "concept", "lang": "en", "question": "What is the order of carbocation stability?", "steps": ["Alkyl groups donate electron density.", "More substitution means more stable.", "Order: 3 > 2 > 1 > methyl."], "subject": "chemistry", "text": "Answer: Tertiary > secondary > primary > methyl.\nSteps:\n1. Alkyl groups donate electron density.\n2. More substitution means more stable.\n3. Order: 3 > 2 > 1 > methyl.", "topic": "organic_mechanisms"}
{"answer": "The major product is 2-bromopropane, as H adds to carbon 1 and Br to carbon 2.", "choices": null, "id": "che_0103", "kind": "worked_example", "lang": "en", "question": "Predict the major product of HBr addition to propene.", "steps": ["Apply Markovnikov: H to less substituted C.", "H adds to C1, Br to C2.", "Product: 2-bromopropane."], "subject": "chemistry", "text": "Answer: 2-bromopropane.\nSteps:\n1. Apply Markovnikov: H to less substituted C.\n2. H adds to C1, Br to C2.\n3. Product: 2-bromopropane.", "topic": "organic_mechanisms"}
{"answer": "Karbokation je kladně nabitý uhlík se šesti elektrony, stabilizovaný alkyly.", "choices": null, "id": "che_0104", "kind": "concept", "lang": "cs", "question": "Co je karbokation?", "steps": ["Kladný uhlík, sextet elektronů.", "Planární geometrie.", "Stabilita: terciární nejvyšší."], "subject": "chemistry", "text": "Answer: Kladně nabitý uhlík.\nSteps:\n1. Kladný uhlík, sextet elektronů.\n2. Planární geometrie.\n3. Stabilita: terciární nejvyšší.", "topic": "organic_mechanisms"}
{"answer": "E2 elimination needs a strong base to remove a proton as the leaving group departs.", "choices": {"A": "Weak base, polar protic", "B": "Strong base, concerted step", "C": "No base at all", "D": "Acid catalyst only"}, "id": "che_0105", "kind": "multiple_choice", "lang": "en", "question": "Which conditions favor E2 elimination?", "steps": ["E2 is concerted with base.", "Strong base removes proton.", "Select option B."], "subject": "chemistry", "text": "Answer: Strong base, concerted step.\nSteps:\n1. E2 is concerted with base.\n2. Strong base removes proton.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "Electrophilic addition breaks the pi bond of an alkene as two groups add across it.", "choices": null, "id": "che_0106", "kind": "concept", "lang": "en", "question": "What is electrophilic addition to alkenes?", "steps": ["Pi bond attacks electrophile.", "Carbocation forms.", "Nucleophile captures it."], "subject": "chemistry", "text": "Answer: Addition across the double bond.\nSteps:\n1. Pi bond attacks electrophile.\n2. Carbocation forms.\n3. Nucleophile captures it.", "topic": "organic_mechanisms"}
{"answer": "Ethene plus H2 over nickel gives ethane, saturating the double bond.", "choices": null, "id": "che_0107", "kind": "worked_example", "lang": "en", "question": "What is the product of ethene hydrogenation (H2, Ni)?", "steps": ["H2 adds across C=C.", "Each carbon gains one H.", "Product: ethane."], "subject": "chemistry", "text": "Answer: Ethane.\nSteps:\n1. H2 adds across C=C.\n2. Each carbon gains one H.\n3. Product: ethane.", "topic": "organic_mechanisms"}
{"answer": "Radical chains run through initiation forming radicals, propagation cycling them, and termination combining them.", "choices": null, "id": "che_0108", "kind": "concept", "lang": "en", "question": "What are the steps of a radical chain reaction?", "steps": ["Initiation creates radicals.", "Propagation sustains the cycle.", "Termination ends it by pairing."], "subject": "chemistry", "text": "Answer: Initiation, propagation, termination.\nSteps:\n1. Initiation creates radicals.\n2. Propagation sustains the cycle.\n3. Termination ends it by pairing.", "topic": "organic_mechanisms"}
{"answer": "Initiation splits a bond homolytically to create the first radicals.", "choices": {"A": "Joins two radicals", "B": "Transfers a radical", "C": "Quenches all radicals", "D": "Creates the first radicals"}, "id": "che_0109", "kind": "multiple_choice", "lang": "en", "question": "What happens in chain initiation?", "steps": ["Recall initiation starts the chain.", "Homolysis creates radicals.", "Select option D."], "subject": "chemistry", "text": "Answer: Creates the first radicals.\nSteps:\n1. Recall initiation starts the chain.\n2. Homolysis creates radicals.\n3. Select option D.\nAnswer: (D)", "topic": "organic_mechanisms"}
{"answer": "Adicí bromu na ethen vzniká 1,2-dibromethan.", "choices": null, "id": "che_0110", "kind": "worked_example", "lang": "cs", "question": "Jaký produkt vznikne adicí Br2 na ethen?", "steps": ["Dvojná vazba se rozštěpí.", "Každý uhlík přijme jeden brom.", "Produkt: 1,2-dibromethan."], "subject": "chemistry", "text": "Answer: 1,2-dibromethan.\nSteps:\n1. Dvojná vazba se rozštěpí.\n2. Každý uhlík přijme jeden brom.\n3. Produkt: 1,2-dibromethan.", "topic": "organic_mechanisms"}
{"answer": "Electrophilic aromatic substitution replaces a ring H with an electrophile while restoring aromaticity.", "choices": null, "id": "che_0111", "kind": "concept", "lang": "en", "question": "What is electrophilic aromatic substitution?", "steps": ["Electrophile attacks the ring.", "Sigma complex forms.", "Base removes H, aromaticity returns."], "subject": "chemistry", "text": "Answer: Ring H replaced by electrophile.\nSteps:\n1. Electrophile attacks the ring.\n2. Sigma complex forms.\n3. Base removes H, aromaticity returns.", "topic": "organic_mechanisms"}
{"answer": "Nitration of benzene with HNO3/H2SO4 gives nitrobenzene plus water.", "choices": null, "id": "che_0112", "kind": "worked_example", "lang": "en", "question": "What is the product of benzene nitration (HNO3, H2SO4)?", "steps": ["NO2+ electrophile forms.", "It substitutes one ring H.", "Product: nitrobenzene."], "subject": "chemistry", "text": "Answer: Nitrobenzene.\nSteps:\n1. NO2+ electrophile forms.\n2. It substitutes one ring H.\n3. Product: nitrobenzene.", "topic": "organic_mechanisms"}
{"answer": "A catalyst speeds reaction by lowering activation energy without being consumed.", "choices": {"A": "Lowers activation energy", "B": "Raises activation energy", "C": "Changes equilibrium", "D": "Is always consumed"}, "id": "che_0113", "kind": "multiple_choice", "lang": "en", "question": "How does a catalyst work?", "steps": ["Recall alternative lower path.", "Activation energy drops.", "Select option A."], "subject": "chemistry", "text": "Answer: Lowers activation energy.\nSteps:\n1. Recall alternative lower path.\n2. Activation energy drops.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "Aktivační energie je minimální energie nutná k dosažení přechodového stavu.", "choices": null, "id": "che_0114", "kind": "concept", "lang": "cs", "question": "Co je aktivační energie?", "steps": ["Energie přechodového stavu.", "Vyšší bariéra = pomalejší reakce.", "Katalyzátor ji snižuje."], "subject": "chemistry", "text": "Answer: Energie nutná k reakci.\nSteps:\n1. Energie přechodového stavu.\n2. Vyšší bariéra = pomalejší reakce.\n3. Katalyzátor ji snižuje.", "topic": "organic_mechanisms"}
{"answer": "Dynamic equilibrium means forward and reverse rates are equal with constant concentrations.", "choices": null, "id": "che_0115", "kind": "concept", "lang": "en", "question": "What is dynamic equilibrium?", "steps": ["Both directions still react.", "Rates become equal.", "Concentrations stay constant."], "subject": "chemistry", "text": "Answer: Equal rates, constant concentrations.\nSteps:\n1. Both directions still react.\n2. Rates become equal.\n3. Concentrations stay constant.", "topic": "equilibrium"}
{"answer": "Kc equals [NH3]^2 divided by [N2][H2]^3, with coefficients as exponents.", "choices": {"A": "[N2][H2]/[NH3]", "B": "[NH3]/([N2][H2])", "C": "[NH3]^2/([N2][H2]^3)", "D": "[N2][H2]^3/[NH3]^2"}, "id": "che_0116", "kind": "multiple_choice", "lang": "en", "question": "What is Kc for N2 + 3H2 <-> 2NH3?", "steps": ["Products over reactants.", "Apply exponents 2, 1, 3.", "Select option C."], "subject": "chemistry", "text": "Answer: [NH3]^2/([N2][H2]^3).\nSteps:\n1. Products over reactants.\n2. Apply exponents 2, 1, 3.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "Kc is 8.0, from 2.0 divided by (0.50 x 0.50).", "choices": null, "id": "che_0117", "kind": "worked_example", "lang": "en", "question": "For A + B <-> C with [A] = 0.50 M, [B] = 0.50 M, [C] = 2.0 M, compute Kc.", "steps": ["Write: Kc = [C]/([A][B]).", "Substitute: 2.0 / (0.50 x 0.50).", "Kc = 8.0."], "subject": "chemistry", "text": "Answer: 8.0.\nSteps:\n1. Write: Kc = [C]/([A][B]).\n2. Substitute: 2.0 / (0.50 x 0.50).\n3. Kc = 8.0.", "topic": "equilibrium"}
{"answer": "Rovnovážná konstanta je poměr koncentrací produktů a reaktantů v rovnováze.", "choices": null, "id": "che_0118", "kind": "concept", "lang": "cs", "question": "Co je rovnovážná konstanta?", "steps": ["Poměr produkty/reaktanty.", "Koeficienty jako exponenty.", "Velká K = převaha produktů."], "subject": "chemistry", "text": "Answer: Poměr koncentrací v rovnováze.\nSteps:\n1. Poměr produkty/reaktanty.\n2. Koeficienty jako exponenty.\n3. Velká K = převaha produktů.", "topic": "equilibrium"}
{"answer": "A very large K means products dominate at equilibrium.", "choices": {"A": "Reactants dominate", "B": "Products dominate", "C": "Nothing reacts", "D": "K is meaningless"}, "id": "che_0119", "kind": "multiple_choice", "lang": "en", "question": "What does a very large equilibrium constant mean?", "steps": ["K = products/reactants.", "Large K favors numerator.", "Select option B."], "subject": "chemistry", "text": "Answer: Products dominate.\nSteps:\n1. K = products/reactants.\n2. Large K favors numerator.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "Le Chatelier's principle states a system shifts to counteract an imposed change.", "choices": null, "id": "che_0120", "kind": "concept", "lang": "en", "question": "What is Le Chatelier's principle?", "steps": ["Apply stress: concentration, pressure, heat.", "System shifts to relieve it.", "New equilibrium results."], "subject": "chemistry", "text": "Answer: Systems counteract imposed changes.\nSteps:\n1. Apply stress: concentration, pressure, heat.\n2. System shifts to relieve it.\n3. New equilibrium results.", "topic": "equilibrium"}
{"answer": "The system shifts right toward products because Q = 2 is less than K = 10.", "choices": null, "id": "che_0121", "kind": "worked_example", "lang": "en", "question": "For a reaction with Q = 2 and K = 10, which way does it shift?", "steps": ["Compare Q to K: 2 < 10.", "Too many reactants.", "Shifts right to products."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Compare Q to K: 2 < 10.\n2. Too many reactants.\n3. Shifts right to products.", "topic": "equilibrium"}
{"answer": "Higher pressure favors the side with fewer moles of gas.", "choices": {"A": "More moles of gas", "B": "No shift ever", "C": "Only liquids", "D": "Fewer moles of gas"}, "id": "che_0122", "kind": "multiple_choice", "lang": "en", "question": "How does increased pressure shift gas equilibrium?", "steps": ["System relieves pressure.", "Fewer gas moles reduce pressure.", "Select option D."], "subject": "chemistry", "text": "Answer: Fewer moles of gas.\nSteps:\n1. System relieves pressure.\n2. Fewer gas moles reduce pressure.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "Catalysts speed both directions equally, so equilibrium position and K stay unchanged.", "choices": null, "id": "che_0123", "kind": "concept", "lang": "en", "question": "Do catalysts shift equilibrium?", "steps": ["Both rates rise equally.", "K stays the same.", "Equilibrium reached faster only."], "subject": "chemistry", "text": "Answer: No, only faster to reach it.\nSteps:\n1. Both rates rise equally.\n2. K stays the same.\n3. Equilibrium reached faster only.", "topic": "equilibrium"}
{"answer": "Kc je 2,0, protože 3,0 děleno 1,5 se rovná 2,0.", "choices": null, "id": "che_0124", "kind": "worked_example", "lang": "cs", "question": "Pro A <-> B je [A] = 1,5 M a [B] = 3,0 M. Vypočítej Kc.", "steps": ["Napiš vzorec: Kc = [B]/[A].", "Dosaď: 3,0 / 1,5.", "Kc = 2,0."], "subject": "chemistry", "text": "Answer: 2,0.\nSteps:\n1. Napiš vzorec: Kc = [B]/[A].\n2. Dosaď: 3,0 / 1,5.\n3. Kc = 2,0.", "topic": "equilibrium"}
{"answer": "Adding heat to an endothermic reaction shifts it right, toward products.", "choices": {"A": "Shifts right", "B": "Shifts left", "C": "No shift", "D": "K becomes zero"}, "id": "che_0125", "kind": "multiple_choice", "lang": "en", "question": "Heating an endothermic reaction shifts it which way?", "steps": ["Heat acts as reactant.", "Adding reactant shifts right.", "Select option A."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Heat acts as reactant.\n2. Adding reactant shifts right.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "ICE tables track initial, change, and equilibrium concentrations to solve for unknowns.", "choices": null, "id": "che_0126", "kind": "concept", "lang": "en", "question": "What is an ICE table?", "steps": ["List initial concentrations.", "Define change as x.", "Solve equilibrium row with K."], "subject": "chemistry", "text": "Answer: Initial-change-equilibrium tracker.\nSteps:\n1. List initial concentrations.\n2. Define change as x.\n3. Solve equilibrium row with K.", "topic": "equilibrium"}
{"answer": "Equilibrium [B] is 0.80 M, solving x/(1.0 - x) = 4.", "choices": null, "id": "che_0127", "kind": "worked_example", "lang": "en", "question": "For A <-> B with K = 4 and [A]0 = 1.0 M, find [B] at equilibrium.", "steps": ["Write: x / (1.0 - x) = 4.", "Solve: x = 4 - 4x, 5x = 4.", "[B] = x = 0.80 M."], "subject": "chemistry", "text": "Answer: 0.80 M.\nSteps:\n1. Write: x / (1.0 - x) = 4.\n2. Solve: x = 4 - 4x, 5x = 4.\n3. [B] = x = 0.80 M.", "topic": "equilibrium"}
{"answer": "Kp is written with partial pressures instead of molar concentrations.", "choices": {"A": "Molar masses", "B": "Mole counts", "C": "Partial pressures", "D": "Volumes"}, "id": "che_0128", "kind": "multiple_choice", "lang": "en", "question": "What does Kp use in its expression?", "steps": ["Recall p means pressure.", "Use partial pressures.", "Select option C."], "subject": "chemistry", "text": "Answer: Partial pressures.\nSteps:\n1. Recall p means pressure.\n2. Use partial pressures.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "Homogeneous equilibria have one phase while heterogeneous equilibria mix phases, omitting pure solids and liquids from K.", "choices": null, "id": "che_0129", "kind": "concept", "lang": "en", "question": "How do homogeneous and heterogeneous equilibria differ?", "steps": ["Homogeneous: single phase.", "Heterogeneous: multiple phases.", "Omit solids and liquids from K."], "subject": "chemistry", "text": "Answer: One phase versus mixed phases.\nSteps:\n1. Homogeneous: single phase.\n2. Heterogeneous: multiple phases.\n3. Omit solids and liquids from K.", "topic": "equilibrium"}
{"answer": "Le Chatelierův princip říká, že soustava se posune proti vnější změně.", "choices": null, "id": "che_0130", "kind": "concept", "lang": "cs", "question": "Co říká Le Chatelierův princip?", "steps": ["Změna koncentrace, tlaku či teploty.", "Soustava působí proti ní.", "Ustálí se nová rovnováha."], "subject": "chemistry", "text": "Answer: Soustava působí proti změně.\nSteps:\n1. Změna koncentrace, tlaku či teploty.\n2. Soustava působí proti ní.\n3. Ustálí se nová rovnováha.", "topic": "equilibrium"}
{"answer": "Adding reactant drives the system toward products to consume the excess.", "choices": {"A": "Shifts left", "B": "Shifts right", "C": "No shift", "D": "K triples"}, "id": "che_0131", "kind": "multiple_choice", "lang": "en", "question": "What happens when a reactant is added at equilibrium?", "steps": ["Excess reactant present.", "System consumes it.", "Select option B."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Excess reactant present.\n2. System consumes it.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "Kp is 12.2, from 0.50 x 0.08206 x 298.", "choices": null, "id": "che_0132", "kind": "worked_example", "lang": "en", "question": "For N2O4 <-> 2NO2 with Kc = 0.50 at 298 K, compute Kp (R = 0.08206 L atm/mol K).", "steps": ["Δn = 2 - 1 = 1.", "Kp = 0.50 x 0.08206 x 298.", "Kp = 12.2."], "subject": "chemistry", "text": "Answer: 12.2.\nSteps:\n1. Δn = 2 - 1 = 1.\n2. Kp = 0.50 x 0.08206 x 298.\n3. Kp = 12.2.", "topic": "equilibrium"}
{"answer": "Galvanic cells release energy spontaneously while electrolytic cells consume energy to force reaction.", "choices": null, "id": "che_0133", "kind": "concept", "lang": "en", "question": "How do galvanic and electrolytic cells differ?", "steps": ["Galvanic: spontaneous, E positive.", "Electrolytic: forced, E negative.", "Example: battery versus plating."], "subject": "chemistry", "text": "Answer: Spontaneous versus driven cells.\nSteps:\n1. Galvanic: spontaneous, E positive.\n2. Electrolytic: forced, E negative.\n3. Example: battery versus plating.", "topic": "electrochemistry"}
{"answer": "Oxidation occurs at the anode, remembered as AN OX.", "choices": {"A": "Anode is oxidation", "B": "Anode is reduction", "C": "Anode is neutral", "D": "Anode stores ions"}, "id": "che_0134", "kind": "multiple_choice", "lang": "en", "question": "What happens at the anode?", "steps": ["Recall AN OX mnemonic.", "Anode loses electrons.", "Select option A."], "subject": "chemistry", "text": "Answer: Anode is oxidation.\nSteps:\n1. Recall AN OX mnemonic.\n2. Anode loses electrons.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "The standard cell potential is 1.10 V, from 0.34 - (-0.76).", "choices": null, "id": "che_0135", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Zn/Cu with E(Cu) = 0.34 V and E(Zn) = -0.76 V.", "steps": ["Cathode is Cu at 0.34 V.", "Anode is Zn at -0.76 V.", "E = 0.34 - (-0.76) = 1.10 V."], "subject": "chemistry", "text": "Answer: 1.10 V.\nSteps:\n1. Cathode is Cu at 0.34 V.\n2. Anode is Zn at -0.76 V.\n3. E = 0.34 - (-0.76) = 1.10 V.", "topic": "electrochemistry"}
{"answer": "Galvanický článek mění chemickou energii samovolné reakce na elektrickou.", "choices": null, "id": "che_0136", "kind": "concept", "lang": "cs", "question": "Co je galvanický článek?", "steps": ["Samovolná redoxní reakce.", "Elektrony tečou vnějším obvodem.", "Příklad: Daniellův článek."], "subject": "chemistry", "text": "Answer: Zdroj proudu z chemie.\nSteps:\n1. Samovolná redoxní reakce.\n2. Elektrony tečou vnějším obvodem.\n3. Příklad: Daniellův článek.", "topic": "electrochemistry"}
{"answer": "Electrons flow from anode to cathode through the external wire.", "choices": {"A": "Cathode to anode", "B": "Anode to cathode", "C": "Both directions", "D": "Through the salt bridge"}, "id": "che_0137", "kind": "multiple_choice", "lang": "en", "question": "Which way do electrons flow in a galvanic cell?", "steps": ["Anode releases electrons.", "Wire carries them to cathode.", "Select option B."], "subject": "chemistry", "text": "Answer: Anode to cathode.\nSteps:\n1. Anode releases electrons.\n2. Wire carries them to cathode.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "The standard hydrogen electrode is assigned exactly 0.00 V as the reference.", "choices": null, "id": "che_0138", "kind": "concept", "lang": "en", "question": "What is the standard hydrogen electrode?", "steps": ["H2 gas over platinum.", "1 M H+ at 1 atm.", "Defined as 0.00 V."], "subject": "chemistry", "text": "Answer: Reference electrode at 0.00 V.\nSteps:\n1. H2 gas over platinum.\n2. 1 M H+ at 1 atm.\n3. Defined as 0.00 V.", "topic": "electrochemistry"}
{"answer": "ΔG is -212 kJ, from -2 x 96485 x 1.10 J.", "choices": null, "id": "che_0139", "kind": "worked_example", "lang": "en", "question": "Compute ΔG for a cell with n = 2 and E = 1.10 V (F = 96485 C/mol).", "steps": ["Write: ΔG = -nFE.", "Substitute: -2 x 96485 x 1.10.", "ΔG = -212,267 J = -212 kJ."], "subject": "chemistry", "text": "Answer: -212 kJ.\nSteps:\n1. Write: ΔG = -nFE.\n2. Substitute: -2 x 96485 x 1.10.\n3. ΔG = -212,267 J = -212 kJ.", "topic": "electrochemistry"}
{"answer": "The Nernst equation adjusts cell potential for nonstandard concentrations via Q.", "choices": null, "id": "che_0140", "kind": "concept", "lang": "en", "question": "What is the Nernst equation?", "steps": ["E = E° - (RT/nF) ln Q.", "At 25 C: E° - (0.0592/n) log Q.", "Q reflects concentrations."], "subject": "chemistry", "text": "Answer: E from E° and reaction quotient.\nSteps:\n1. E = E° - (RT/nF) ln Q.\n2. At 25 C: E° - (0.0592/n) log Q.\n3. Q reflects concentrations.", "topic": "electrochemistry"}
{"answer": "In electrolysis the cathode is negative, attracting cations.", "choices": {"A": "Positive", "B": "Neutral", "C": "Negative", "D": "Absent"}, "id": "che_0141", "kind": "multiple_choice", "lang": "en", "question": "What is the cathode's sign in an electrolytic cell?", "steps": ["External supply drives electrons in.", "Cathode receives electrons.", "Select option C."], "subject": "chemistry", "text": "Answer: Negative.\nSteps:\n1. External supply drives electrons in.\n2. Cathode receives electrons.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "The cell potential is 1.07 V, from 1.10 - (0.0592/2) x log(10).", "choices": null, "id": "che_0142", "kind": "worked_example", "lang": "en", "question": "E° = 1.10 V, n = 2, Q = 10 at 25 C. Compute E.", "steps": ["Write: E = 1.10 - (0.0592/2) log Q.", "Substitute: 1.10 - 0.0296 x 1.", "E = 1.07 V."], "subject": "chemistry", "text": "Answer: 1.07 V.\nSteps:\n1. Write: E = 1.10 - (0.0592/2) log Q.\n2. Substitute: 1.10 - 0.0296 x 1.\n3. E = 1.07 V.", "topic": "electrochemistry"}
{"answer": "Napětí Daniellova článku je 1,10 V, protože 0,34 - (-0,76) = 1,10.", "choices": null, "id": "che_0143", "kind": "worked_example", "lang": "cs", "question": "Vypočítej napětí článku Zn/Cu: E(Cu) = 0,34 V, E(Zn) = -0,76 V.", "steps": ["Katoda Cu: 0,34 V.", "Anoda Zn: -0,76 V.", "E = 0,34 - (-0,76) = 1,10 V."], "subject": "chemistry", "text": "Answer: 1,10 V.\nSteps:\n1. Katoda Cu: 0,34 V.\n2. Anoda Zn: -0,76 V.\n3. E = 0,34 - (-0,76) = 1,10 V.", "topic": "electrochemistry"}
{"answer": "Faraday's laws state deposited mass is proportional to charge passed and equivalent weight.", "choices": null, "id": "che_0144", "kind": "concept", "lang": "en", "question": "What are Faraday's laws of electrolysis?", "steps": ["Charge: Q = I x t.", "Moles electrons = Q / F.", "Mass from moles and molar mass."], "subject": "chemistry", "text": "Answer: Mass proportional to charge.\nSteps:\n1. Charge: Q = I x t.\n2. Moles electrons = Q / F.\n3. Mass from moles and molar mass.", "topic": "electrochemistry"}
{"answer": "One mole of electrons carries 96,485 coulombs, the Faraday constant.", "choices": {"A": "6,022 C/mol", "B": "8,314 C/mol", "C": "1,602 C/mol", "D": "96,485 C/mol"}, "id": "che_0145", "kind": "multiple_choice", "lang": "en", "question": "What is the Faraday constant?", "steps": ["Recall charge per mole electrons.", "Value 96,485 C/mol.", "Select option D."], "subject": "chemistry", "text": "Answer: 96,485 C/mol.\nSteps:\n1. Recall charge per mole electrons.\n2. Value 96,485 C/mol.\n3. Select option D.\nAnswer: (D)", "topic": "electrochemistry"}
{"answer": "The plated copper mass is 2.37 g, from 7200 C giving 0.0373 mol Cu.", "choices": null, "id": "che_0146", "kind": "worked_example", "lang": "en", "question": "What mass of Cu plates at 2.00 A for 1.00 hour (M = 63.55 g/mol)?", "steps": ["Q = 2.00 x 3600 = 7200 C.", "Mol e- = 7200/96485 = 0.0746; Cu = 0.0373 mol.", "Mass = 0.0373 x 63.55 = 2.37 g."], "subject": "chemistry", "text": "Answer: 2.37 g.\nSteps:\n1. Q = 2.00 x 3600 = 7200 C.\n2. Mol e- = 7200/96485 = 0.0746; Cu = 0.0373 mol.\n3. Mass = 0.0373 x 63.55 = 2.37 g.", "topic": "electrochemistry"}
{"answer": "Corrosion is spontaneous oxidation of metals like iron forming rust in air and water.", "choices": null, "id": "che_0147", "kind": "concept", "lang": "en", "question": "What is corrosion?", "steps": ["Metal oxidizes at anodic sites.", "Oxygen reduces at cathodic sites.", "Rust is hydrated iron oxide."], "subject": "chemistry", "text": "Answer: Spontaneous metal oxidation.\nSteps:\n1. Metal oxidizes at anodic sites.\n2. Oxygen reduces at cathodic sites.\n3. Rust is hydrated iron oxide.", "topic": "electrochemistry"}
{"answer": "Elektrolýza je rozklad látky stejnosměrným proudem na elektrodách.", "choices": null, "id": "che_0148", "kind": "concept", "lang": "cs", "question": "Co je elektrolýza?", "steps": ["Proud protéká elektrolytem.", "Na katodě redukce, na anodě oxidace.", "Příklad: rozklad vody."], "subject": "chemistry", "text": "Answer: Rozklad proudem.\nSteps:\n1. Proud protéká elektrolytem.\n2. Na katodě redukce, na anodě oxidace.\n3. Příklad: rozklad vody.", "topic": "electrochemistry"}
{"answer": "The salt bridge carries ions to keep each half-cell electrically neutral.", "choices": {"A": "Keeps charge neutrality", "B": "Carries electrons", "C": "Adds reactants", "D": "Cools the cell"}, "id": "che_0149", "kind": "multiple_choice", "lang": "en", "question": "What is the purpose of a salt bridge?", "steps": ["Cells would charge up otherwise.", "Ions migrate to balance.", "Select option A."], "subject": "chemistry", "text": "Answer: Keeps charge neutrality.\nSteps:\n1. Cells would charge up otherwise.\n2. Ions migrate to balance.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "Plating 6.35 g of Cu at 2.00 A takes 2.68 hours.", "choices": null, "id": "che_0150", "kind": "worked_example", "lang": "en", "question": "How long at 2.00 A to plate 6.35 g of Cu (M = 63.55 g/mol)?", "steps": ["Mol Cu = 6.35/63.55 = 0.100; e- = 0.200 mol.", "Q = 0.200 x 96485 = 19,297 C.", "t = 19,297/2.00 = 9,649 s = 2.68 h."], "subject": "chemistry", "text": "Answer: 2.68 h.\nSteps:\n1. Mol Cu = 6.35/63.55 = 0.100; e- = 0.200 mol.\n2. Q = 0.200 x 96485 = 19,297 C.\n3. t = 19,297/2.00 = 9,649 s = 2.68 h.", "topic": "electrochemistry"}
{"answer": "Glucose has molar mass 180.16 g/mol, from 6 C, 12 H, and 6 O atoms.", "choices": null, "id": "che_0151", "kind": "concept", "lang": "en", "question": "How is molar mass found from a formula?", "steps": ["Multiply each atomic mass by its count.", "Sum all contributions.", "Example: glucose totals 180.16 g/mol."], "subject": "chemistry", "text": "Answer: Sum of atomic masses times counts.\nSteps:\n1. Multiply each atomic mass by its count.\n2. Sum all contributions.\n3. Example: glucose totals 180.16 g/mol.", "topic": "stoichiometry"}
{"answer": "There are 0.50 mol, from 90 g divided by 180.16 g/mol.", "choices": {"A": "0.25 mol", "B": "0.50 mol", "C": "1.00 mol", "D": "2.00 mol"}, "id": "che_0152", "kind": "multiple_choice", "lang": "en", "question": "How many moles are in 90 g of glucose (M = 180.16 g/mol)?", "steps": ["Write: n = 90 / 180.16.", "Compute: 0.50 mol.", "Select option B."], "subject": "chemistry", "text": "Answer: 0.50 mol.\nSteps:\n1. Write: n = 90 / 180.16.\n2. Compute: 0.50 mol.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "One mole of methane yields 44.01 g of CO2, a one-to-one mole ratio.", "choices": null, "id": "che_0153", "kind": "worked_example", "lang": "en", "question": "What mass of CO2 forms from burning 1.00 mol of CH4?", "steps": ["Balanced: 1 CH4 gives 1 CO2.", "Moles CO2 = 1.00 mol.", "Mass = 1.00 x 44.01 = 44.01 g."], "subject": "chemistry", "text": "Answer: 44.01 g.\nSteps:\n1. Balanced: 1 CH4 gives 1 CO2.\n2. Moles CO2 = 1.00 mol.\n3. Mass = 1.00 x 44.01 = 44.01 g.", "topic": "stoichiometry"}
{"answer": "Stechiometrie počítá látková množství reaktantů a produktů z vyčíslených rovnic.", "choices": null, "id": "che_0154", "kind": "concept", "lang": "cs", "question": "Co je stechiometrie?", "steps": ["Vyčísli rovnici.", "Převeď na moly.", "Použij poměry koeficientů."], "subject": "chemistry", "text": "Answer: Výpočty z chemických rovnic.\nSteps:\n1. Vyčísli rovnici.\n2. Převeď na moly.\n3. Použij poměry koeficientů.", "topic": "stoichiometry"}
{"answer": "Hydrogen limits because 2 mol H2 can only pair with 0.67 mol N2, leaving N2 in excess.", "choices": {"A": "H2 is limiting", "B": "N2 is limiting", "C": "Both limit equally", "D": "Cannot tell"}, "id": "che_0155", "kind": "multiple_choice", "lang": "en", "question": "For N2 + 3H2 -> 2NH3 with 1 mol N2 and 2 mol H2, which limits?", "steps": ["Need 3 H2 per N2.", "Have only 2 H2 for 1 N2.", "Select option A."], "subject": "chemistry", "text": "Answer: H2 is limiting.\nSteps:\n1. Need 3 H2 per N2.\n2. Have only 2 H2 for 1 N2.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "The theoretical yield is 36.03 g of water, from 2.00 mol times 18.015 g/mol.", "choices": null, "id": "che_0156", "kind": "worked_example", "lang": "en", "question": "What mass of H2O forms from 2.00 mol H2 with excess O2?", "steps": ["Ratio H2:H2O is 1:1.", "Moles water = 2.00 mol.", "Mass = 2.00 x 18.015 = 36.03 g."], "subject": "chemistry", "text": "Answer: 36.03 g.\nSteps:\n1. Ratio H2:H2O is 1:1.\n2. Moles water = 2.00 mol.\n3. Mass = 2.00 x 18.015 = 36.03 g.", "topic": "stoichiometry"}
{"answer": "Percent composition gives each element's mass share; water is 11.2% H and 88.8% O.", "choices": null, "id": "che_0157", "kind": "concept", "lang": "en", "question": "What is percent composition?", "steps": ["Divide element mass by molar mass.", "Multiply by 100.", "Example: water 11.2% H, 88.8% O."], "subject": "chemistry", "text": "Answer: Mass percent of each element.\nSteps:\n1. Divide element mass by molar mass.\n2. Multiply by 100.\n3. Example: water 11.2% H, 88.8% O.", "topic": "stoichiometry"}
{"answer": "Oxygen is 72.7% of CO2, from 32.00 divided by 44.01 times 100.", "choices": null, "id": "che_0158", "kind": "worked_example", "lang": "en", "question": "Compute the mass percent of oxygen in CO2.", "steps": ["O mass = 2 x 16.00 = 32.00.", "Divide: 32.00 / 44.01 = 0.727.", "Percent = 72.7%."], "subject": "chemistry", "text": "Answer: 72.7%.\nSteps:\n1. O mass = 2 x 16.00 = 32.00.\n2. Divide: 32.00 / 44.01 = 0.727.\n3. Percent = 72.7%.", "topic": "stoichiometry"}
{"answer": "The ratio C:H:O is 1:2:1, giving the empirical formula CH2O.", "choices": {"A": "CHO", "B": "C2H4O", "C": "CH2O", "D": "CO2"}, "id": "che_0159", "kind": "multiple_choice", "lang": "en", "question": "A compound is 40.0% C, 6.7% H, 53.3% O. What is its empirical formula?", "steps": ["Moles: C 3.33, H 6.65, O 3.33.", "Divide by 3.33: 1, 2, 1.", "Select option C."], "subject": "chemistry", "text": "Answer: CH2O.\nSteps:\n1. Moles: C 3.33, H 6.65, O 3.33.\n2. Divide by 3.33: 1, 2, 1.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "Hmotnost je 20 g, protože 0,5 krát 40 se rovná 20.", "choices": null, "id": "che_0160", "kind": "worked_example", "lang": "cs", "question": "Jaká je hmotnost 0,5 molu NaOH (M = 40 g/mol)?", "steps": ["Napiš vzorec: m = n x M.", "Dosaď: 0,5 x 40.", "m = 20 g."], "subject": "chemistry", "text": "Answer: 20 g.\nSteps:\n1. Napiš vzorec: m = n x M.\n2. Dosaď: 0,5 x 40.\n3. m = 20 g.", "topic": "stoichiometry"}
{"answer": "A hydrate like CuSO4.5H2O holds a fixed number of water molecules per formula unit.", "choices": null, "id": "che_0161", "kind": "concept", "lang": "en", "question": "What is a hydrate?", "steps": ["Define trapped water in crystals.", "Dot shows fixed ratio.", "Heating drives water off."], "subject": "chemistry", "text": "Answer: Salt with fixed crystal water.\nSteps:\n1. Define trapped water in crystals.\n2. Dot shows fixed ratio.\n3. Heating drives water off.", "topic": "stoichiometry"}
{"answer": "The solution is 1.00 M, from 58.44 g (1.00 mol) in 1.00 L.", "choices": {"A": "0.10 M", "B": "0.50 M", "C": "2.00 M", "D": "1.00 M"}, "id": "che_0162", "kind": "multiple_choice", "lang": "en", "question": "58.44 g of NaCl dissolves in 1.00 L. What is the molarity?", "steps": ["Moles = 58.44/58.44 = 1.00.", "Divide by 1.00 L.", "Select option D."], "subject": "chemistry", "text": "Answer: 1.00 M.\nSteps:\n1. Moles = 58.44/58.44 = 1.00.\n2. Divide by 1.00 L.\n3. Select option D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "There are 0.0500 mol, from 0.250 L times 0.200 M.", "choices": null, "id": "che_0163", "kind": "worked_example", "lang": "en", "question": "How many moles are in 250 mL of 0.200 M solution?", "steps": ["Convert: 250 mL = 0.250 L.", "Multiply: 0.250 x 0.200.", "n = 0.0500 mol."], "subject": "chemistry", "text": "Answer: 0.0500 mol.\nSteps:\n1. Convert: 250 mL = 0.250 L.\n2. Multiply: 0.250 x 0.200.\n3. n = 0.0500 mol.", "topic": "stoichiometry"}
{"answer": "Dilution adds solvent while moles stay fixed, so M1V1 equals M2V2.", "choices": null, "id": "che_0164", "kind": "concept", "lang": "en", "question": "What principle governs dilution?", "steps": ["Moles before equal moles after.", "Write M1V1 = M2V2.", "Volume rises, M falls."], "subject": "chemistry", "text": "Answer: Moles stay fixed; M1V1 = M2V2.\nSteps:\n1. Moles before equal moles after.\n2. Write M1V1 = M2V2.\n3. Volume rises, M falls.", "topic": "stoichiometry"}
{"answer": "Molární koncentrace je počet molů látky v jednom litru roztoku (mol/l).", "choices": null, "id": "che_0165", "kind": "concept", "lang": "cs", "question": "Co je molární koncentrace?", "steps": ["Moly děleno litry.", "Jednotka mol/l (M).", "Příklad: 1 mol v 1 l = 1 M."], "subject": "chemistry", "text": "Answer: Moly na litr roztoku.\nSteps:\n1. Moly děleno litry.\n2. Jednotka mol/l (M).\n3. Příklad: 1 mol v 1 l = 1 M.", "topic": "stoichiometry"}
{"answer": "Nitrogen density is 1.25 g/L, from 28.02 g divided by 22.414 L.", "choices": {"A": "0.63 g/L", "B": "1.25 g/L", "C": "2.50 g/L", "D": "14.0 g/L"}, "id": "che_0166", "kind": "multiple_choice", "lang": "en", "question": "What is the density of N2 gas at STP?", "steps": ["Mass of 1 mol = 28.02 g.", "Volume = 22.414 L.", "Density 1.25; select B."], "subject": "chemistry", "text": "Answer: 1.25 g/L.\nSteps:\n1. Mass of 1 mol = 28.02 g.\n2. Volume = 22.414 L.\n3. Density 1.25; select B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Oxygen density is 1.43 g/L, from 32.00 g divided by 22.414 L.", "choices": null, "id": "che_0167", "kind": "worked_example", "lang": "en", "question": "Compute the density of O2 gas at STP.", "steps": ["Mass of 1 mol = 32.00 g.", "Divide: 32.00 / 22.414.", "Density = 1.43 g/L."], "subject": "chemistry", "text": "Answer: 1.43 g/L.\nSteps:\n1. Mass of 1 mol = 32.00 g.\n2. Divide: 32.00 / 22.414.\n3. Density = 1.43 g/L.", "topic": "stoichiometry"}
{"answer": "Objem je 11,2 l, protože 0,5 krát 22,414 se rovná 11,207.", "choices": null, "id": "che_0168", "kind": "worked_example", "lang": "cs", "question": "Jaký objem má 0,5 molu plynu za STP (22,414 l/mol)?", "steps": ["Napiš vzorec: V = n x 22,414.", "Dosaď: 0,5 x 22,414.", "V = 11,2 l."], "subject": "chemistry", "text": "Answer: 11,2 l.\nSteps:\n1. Napiš vzorec: V = n x 22,414.\n2. Dosaď: 0,5 x 22,414.\n3. V = 11,2 l.", "topic": "stoichiometry"}
{"answer": "The excess reactant is left over after the limiting one is consumed.", "choices": {"A": "Limits the yield", "B": "Is fully consumed", "C": "Remains after reaction", "D": "Never participates"}, "id": "che_0169", "kind": "multiple_choice", "lang": "en", "question": "What is true of the excess reactant?", "steps": ["Limiting reactant sets yield.", "Excess is more than needed.", "Select option C."], "subject": "chemistry", "text": "Answer: Remains after reaction.\nSteps:\n1. Limiting reactant sets yield.\n2. Excess is more than needed.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "Strong acids dissociate fully while weak acids only partly ionize in water.", "choices": null, "id": "che_0170", "kind": "concept", "lang": "en", "question": "How do strong and weak acids differ?", "steps": ["Strong: ~100% dissociation.", "Weak: equilibrium with Ka.", "Example: HCl versus acetic acid."], "subject": "chemistry", "text": "Answer: Full versus partial dissociation.\nSteps:\n1. Strong: ~100% dissociation.\n2. Weak: equilibrium with Ka.\n3. Example: HCl versus acetic acid.", "topic": "acids_bases"}
{"answer": "Sodium hydroxide is a strong base that dissociates fully.", "choices": {"A": "NaOH", "B": "NH3", "C": "CH3NH2", "D": "C5H5N"}, "id": "che_0171", "kind": "multiple_choice", "lang": "en", "question": "Which of these is a strong base?", "steps": ["Group 1 hydroxides are strong.", "Eliminate ammonia and amines.", "Select option A."], "subject": "chemistry", "text": "Answer: NaOH.\nSteps:\n1. Group 1 hydroxides are strong.\n2. Eliminate ammonia and amines.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "The pOH is 11.00, since pH 3.00 gives 14 - 3 = 11.", "choices": null, "id": "che_0172", "kind": "worked_example", "lang": "en", "question": "Compute the pOH of 0.0010 M HCl.", "steps": ["pH = -log(0.0010) = 3.00.", "pOH = 14 - pH.", "pOH = 11.00."], "subject": "chemistry", "text": "Answer: 11.00.\nSteps:\n1. pH = -log(0.0010) = 3.00.\n2. pOH = 14 - pH.\n3. pOH = 11.00.", "topic": "acids_bases"}
{"answer": "Silná kyselina ve vodě disociuje prakticky úplně.", "choices": null, "id": "che_0173", "kind": "concept", "lang": "cs", "question": "Co je silná kyselina?", "steps": ["Úplná disociace.", "Příklady: HCl, HNO3, H2SO4.", "Kontrast se slabými kyselinami."], "subject": "chemistry", "text": "Answer: Kyselina s úplnou disociací.\nSteps:\n1. Úplná disociace.\n2. Příklady: HCl, HNO3, H2SO4.\n3. Kontrast se slabými kyselinami.", "topic": "acids_bases"}
{"answer": "Adding a proton to NH3 gives its conjugate acid NH4+.", "choices": {"A": "NH2(-)", "B": "NH4(+)", "C": "NO3(-)", "D": "N2"}, "id": "che_0174", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate acid of ammonia?", "steps": ["Add one H+ to NH3.", "Result is NH4+.", "Select option B."], "subject": "chemistry", "text": "Answer: NH4+.\nSteps:\n1. Add one H+ to NH3.\n2. Result is NH4+.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "Amphiprotic species like water and HCO3- can both donate and accept protons.", "choices": null, "id": "che_0175", "kind": "concept", "lang": "en", "question": "What does amphiprotic mean?", "steps": ["Can act as acid or base.", "Examples: H2O, HCO3-.", "Depends on partner."], "subject": "chemistry", "text": "Answer: Both donates and accepts protons.\nSteps:\n1. Can act as acid or base.\n2. Examples: H2O, HCO3-.\n3. Depends on partner.", "topic": "acids_bases"}
{"answer": "Hydroxide concentration is 1.0 x 10^-5 M, from pOH = 14 - 9 = 5.", "choices": null, "id": "che_0176", "kind": "worked_example", "lang": "en", "question": "A solution has pH 9.00. Compute [OH-].", "steps": ["pOH = 14 - 9.00 = 5.00.", "Write: [OH-] = 10^(-pOH).", "[OH-] = 1.0 x 10^-5 M."], "subject": "chemistry", "text": "Answer: 1.0 x 10^-5 M.\nSteps:\n1. pOH = 14 - 9.00 = 5.00.\n2. Write: [OH-] = 10^(-pOH).\n3. [OH-] = 1.0 x 10^-5 M.", "topic": "acids_bases"}
{"answer": "A larger Ka means a stronger acid that donates protons more readily.", "choices": null, "id": "che_0177", "kind": "concept", "lang": "en", "question": "How does Ka relate to acid strength?", "steps": ["Ka measures dissociation.", "Bigger Ka means stronger acid.", "pKa inverts the scale."], "subject": "chemistry", "text": "Answer: Larger Ka means stronger acid.\nSteps:\n1. Ka measures dissociation.\n2. Bigger Ka means stronger acid.\n3. pKa inverts the scale.", "topic": "acids_bases"}
{"answer": "The acid with the largest Ka dissociates most and is strongest.", "choices": {"A": "Smallest Ka", "B": "Ka near 1", "C": "Largest Ka", "D": "Ka is irrelevant"}, "id": "che_0178", "kind": "multiple_choice", "lang": "en", "question": "Which acid is strongest?", "steps": ["Compare Ka values.", "Largest Ka wins.", "Select option C."], "subject": "chemistry", "text": "Answer: Largest Ka.\nSteps:\n1. Compare Ka values.\n2. Largest Ka wins.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "pH je 1, protože -log(0,1) = 1.", "choices": null, "id": "che_0179", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,1 M HCl.", "steps": ["HCl disociuje plně.", "pH = -log(0,1).", "pH = 1."], "subject": "chemistry", "text": "Answer: 1.\nSteps:\n1. HCl disociuje plně.\n2. pH = -log(0,1).\n3. pH = 1.", "topic": "acids_bases"}
{"answer": "The common ion effect suppresses weak electrolyte dissociation when a shared ion is added.", "choices": null, "id": "che_0180", "kind": "concept", "lang": "en", "question": "What is the common ion effect?", "steps": ["Add ion shared with equilibrium.", "Equilibrium shifts back.", "Dissociation drops."], "subject": "chemistry", "text": "Answer: Shared ion suppresses dissociation.\nSteps:\n1. Add ion shared with equilibrium.\n2. Equilibrium shifts back.\n3. Dissociation drops.", "topic": "acids_bases"}
{"answer": "Acetate suppresses acetic acid dissociation, so pH rises.", "choices": {"A": "pH falls sharply", "B": "pH rises", "C": "Nothing changes", "D": "Acid strengthens"}, "id": "che_0181", "kind": "multiple_choice", "lang": "en", "question": "What happens adding sodium acetate to acetic acid?", "steps": ["Common acetate ion added.", "Dissociation suppressed.", "Select option B."], "subject": "chemistry", "text": "Answer: pH rises.\nSteps:\n1. Common acetate ion added.\n2. Dissociation suppressed.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "The buffer pH is 4.76, equal to pKa when the ratio is 1:1.", "choices": null, "id": "che_0182", "kind": "worked_example", "lang": "en", "question": "An acetate buffer has equal acid and base (pKa = 4.76). Find pH.", "steps": ["Write: pH = pKa + log(base/acid).", "Ratio 1 gives log 1 = 0.", "pH = 4.76."], "subject": "chemistry", "text": "Answer: 4.76.\nSteps:\n1. Write: pH = pKa + log(base/acid).\n2. Ratio 1 gives log 1 = 0.\n3. pH = 4.76.", "topic": "acids_bases"}
{"answer": "The Henderson-Hasselbalch equation gives buffer pH from pKa and the base-to-acid ratio.", "choices": null, "id": "che_0183", "kind": "concept", "lang": "en", "question": "What is the Henderson-Hasselbalch equation?", "steps": ["pH = pKa + log([A-]/[HA]).", "Use for buffers.", "Equal parts give pH = pKa."], "subject": "chemistry", "text": "Answer: Buffer pH from pKa and ratio.\nSteps:\n1. pH = pKa + log([A-]/[HA]).\n2. Use for buffers.\n3. Equal parts give pH = pKa.", "topic": "acids_bases"}
{"answer": "Pufr je roztok slabé kyseliny a její soli, který odolává změnám pH.", "choices": null, "id": "che_0184", "kind": "concept", "lang": "cs", "question": "Co je pufr (tlumivý roztok)?", "steps": ["Slabá kyselina + sůl.", "Váže přidané H+ i OH-.", "Příklad: octanový pufr."], "subject": "chemistry", "text": "Answer: Roztok stabilizující pH.\nSteps:\n1. Slabá kyselina + sůl.\n2. Váže přidané H+ i OH-.\n3. Příklad: octanový pufr.", "topic": "acids_bases"}
{"answer": "Strong acid with strong base gives neutral salt water, so equivalence pH is 7.", "choices": {"A": "pH 7", "B": "pH 4", "C": "pH 10", "D": "pH 1"}, "id": "che_0185", "kind": "multiple_choice", "lang": "en", "question": "What is the equivalence pH of HCl titrated with NaOH?", "steps": ["Salt NaCl is neutral.", "Only water remains.", "Select option A."], "subject": "chemistry", "text": "Answer: pH 7.\nSteps:\n1. Salt NaCl is neutral.\n2. Only water remains.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "There are 10 mmol, from 50 mL times 0.200 M.", "choices": null, "id": "che_0186", "kind": "worked_example", "lang": "en", "question": "How many millimoles are in 50.0 mL of 0.200 M acid?", "steps": ["Write: mmol = mL x M.", "Substitute: 50.0 x 0.200.", "mmol = 10.0."], "subject": "chemistry", "text": "Answer: 10.0 mmol.\nSteps:\n1. Write: mmol = mL x M.\n2. Substitute: 50.0 x 0.200.\n3. mmol = 10.0.", "topic": "acids_bases"}
{"answer": "[OH-] je 1 x 10^-4 M, protože 10 na -4 odpovídá pOH 4.", "choices": null, "id": "che_0187", "kind": "worked_example", "lang": "cs", "question": "Roztok má pOH 4. Vypočítej [OH-].", "steps": ["Napiš vzorec: [OH-] = 10^(-pOH).", "Dosaď: 10^(-4).", "[OH-] = 1 x 10^-4 M."], "subject": "chemistry", "text": "Answer: 1 x 10^-4 M.\nSteps:\n1. Napiš vzorec: [OH-] = 10^(-pOH).\n2. Dosaď: 10^(-4).\n3. [OH-] = 1 x 10^-4 M.", "topic": "acids_bases"}
{"answer": "The anion hydrolyzes to make OH-, so the solution is basic.", "choices": {"A": "Acidic", "B": "Neutral", "C": "Cannot tell", "D": "Basic"}, "id": "che_0188", "kind": "multiple_choice", "lang": "en", "question": "A salt of a weak acid and strong base gives what solution?", "steps": ["Anion of weak acid hydrolyzes.", "OH- forms.", "Select option D."], "subject": "chemistry", "text": "Answer: Basic.\nSteps:\n1. Anion of weak acid hydrolyzes.\n2. OH- forms.\n3. Select option D.\nAnswer: (D)", "topic": "acids_bases"}
{"answer": "Oxidation numbers track electron bookkeeping: elements are 0, oxygen usually -2, hydrogen usually +1.", "choices": null, "id": "che_0189", "kind": "concept", "lang": "en", "question": "What are the basic oxidation number rules?", "steps": ["Elements: 0.", "O usually -2, H usually +1.", "Sum matches total charge."], "subject": "chemistry", "text": "Answer: Bookkeeping rules summing to charge.\nSteps:\n1. Elements: 0.\n2. O usually -2, H usually +1.\n3. Sum matches total charge.", "topic": "redox"}
{"answer": "Iron is +3, since 2Fe + 3(-2) = 0 gives Fe = +3.", "choices": {"A": "+1", "B": "+2", "C": "+3", "D": "+6"}, "id": "che_0190", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of iron in Fe2O3?", "steps": ["Assign O -2.", "Solve: 2Fe - 6 = 0.", "Fe = +3; select C."], "subject": "chemistry", "text": "Answer: +3.\nSteps:\n1. Assign O -2.\n2. Solve: 2Fe - 6 = 0.\n3. Fe = +3; select C.\nAnswer: (C)", "topic": "redox"}
{"answer": "Nitrogen is +5, since N + 3(-2) = -1 gives N = +5.", "choices": null, "id": "che_0191", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of N in NO3-.", "steps": ["Assign O -2.", "Equation: N - 6 = -1.", "N = +5."], "subject": "chemistry", "text": "Answer: +5.\nSteps:\n1. Assign O -2.\n2. Equation: N - 6 = -1.\n3. N = +5.", "topic": "redox"}
{"answer": "Oxidační číslo je pomyslný náboj atomu přiřazený podle elektronegativity.", "choices": null, "id": "che_0192", "kind": "concept", "lang": "cs", "question": "Co je oxidační číslo?", "steps": ["Pomyslný náboj atomu.", "Součet = náboj částice.", "Slouží k bilanci redoxu."], "subject": "chemistry", "text": "Answer: Pomyslný náboj pro bilanci.\nSteps:\n1. Pomyslný náboj atomu.\n2. Součet = náboj částice.\n3. Slouží k bilanci redoxu.", "topic": "redox"}
{"answer": "The oxidized species loses electrons and its oxidation number rises.", "choices": {"A": "Loses electrons", "B": "Gains electrons", "C": "Loses protons", "D": "Stays unchanged"}, "id": "che_0193", "kind": "multiple_choice", "lang": "en", "question": "What happens to the species being oxidized?", "steps": ["Oxidation means loss.", "Electrons are lost.", "Select option A."], "subject": "chemistry", "text": "Answer: Loses electrons.\nSteps:\n1. Oxidation means loss.\n2. Electrons are lost.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "The balanced equation is Mg + 2HCl -> MgCl2 + H2.", "choices": null, "id": "che_0194", "kind": "worked_example", "lang": "en", "question": "Balance: Mg + HCl -> MgCl2 + H2.", "steps": ["Balance Cl with 2 HCl.", "Check H: 2 each side.", "Result: Mg + 2HCl -> MgCl2 + H2."], "subject": "chemistry", "text": "Answer: Mg + 2HCl -> MgCl2 + H2.\nSteps:\n1. Balance Cl with 2 HCl.\n2. Check H: 2 each side.\n3. Result: Mg + 2HCl -> MgCl2 + H2.", "topic": "redox"}
{"answer": "The half-reaction method splits oxidation and reduction, balances each, then recombines them.", "choices": null, "id": "che_0195", "kind": "concept", "lang": "en", "question": "What is the half-reaction method?", "steps": ["Split redox into two halves.", "Balance atoms and charge each.", "Add halves, cancel electrons."], "subject": "chemistry", "text": "Answer: Balance halves, then combine.\nSteps:\n1. Split redox into two halves.\n2. Balance atoms and charge each.\n3. Add halves, cancel electrons.", "topic": "redox"}
{"answer": "Three electrons are lost as Al goes from 0 to +3.", "choices": null, "id": "che_0196", "kind": "worked_example", "lang": "en", "question": "How many electrons are lost in Al -> Al3+?", "steps": ["Change: 0 to +3.", "Loss = 3 units.", "Electrons lost = 3."], "subject": "chemistry", "text": "Answer: 3 electrons.\nSteps:\n1. Change: 0 to +3.\n2. Loss = 3 units.\n3. Electrons lost = 3.", "topic": "redox"}
{"answer": "Fluorine is the strongest elemental oxidizing agent due to extreme electronegativity.", "choices": {"A": "Na", "B": "Fe", "C": "H2", "D": "F2"}, "id": "che_0197", "kind": "multiple_choice", "lang": "en", "question": "Which is the strongest oxidizing agent?", "steps": ["Oxidizers gain electrons eagerly.", "Fluorine tops the scale.", "Select option D."], "subject": "chemistry", "text": "Answer: F2.\nSteps:\n1. Oxidizers gain electrons eagerly.\n2. Fluorine tops the scale.\n3. Select option D.\nAnswer: (D)", "topic": "redox"}
{"answer": "Síra má oxidační číslo +4, protože S + 2(-2) = 0 dává S = +4.", "choices": null, "id": "che_0198", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo síry v SO2.", "steps": ["Přiřaď O -2.", "Rovnice: S - 4 = 0.", "S = +4."], "subject": "chemistry", "text": "Answer: +4.\nSteps:\n1. Přiřaď O -2.\n2. Rovnice: S - 4 = 0.\n3. S = +4.", "topic": "redox"}
{"answer": "Combustion oxidizes fuel while oxygen is reduced to water and carbon dioxide.", "choices": null, "id": "che_0199", "kind": "concept", "lang": "en", "question": "Why is combustion a redox reaction?", "steps": ["Fuel carbons oxidize.", "Oxygen reduces to oxides.", "Electrons transfer with heat release."], "subject": "chemistry", "text": "Answer: Fuel oxidizes, oxygen reduces.\nSteps:\n1. Fuel carbons oxidize.\n2. Oxygen reduces to oxides.\n3. Electrons transfer with heat release.", "topic": "redox"}
{"answer": "Methane combustion changes oxidation states, unlike the non-redox choices.", "choices": {"A": "HCl + NaOH -> NaCl + H2O", "B": "CH4 + 2O2 -> CO2 + 2H2O", "C": "NaCl dissolving", "D": "Ice melting"}, "id": "che_0200", "kind": "multiple_choice", "lang": "en", "question": "Which reaction is a redox reaction?", "steps": ["Need oxidation number change.", "Only combustion qualifies.", "Select option B."], "subject": "chemistry", "text": "Answer: CH4 + 2O2 -> CO2 + 2H2O.\nSteps:\n1. Need oxidation number change.\n2. Only combustion qualifies.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "The balanced equation is 2Na + Cl2 -> 2NaCl.", "choices": null, "id": "che_0201", "kind": "worked_example", "lang": "en", "question": "Balance: Na + Cl2 -> NaCl.", "steps": ["Balance Cl with 2 NaCl.", "Balance Na with 2 Na.", "Result: 2Na + Cl2 -> 2NaCl."], "subject": "chemistry", "text": "Answer: 2Na + Cl2 -> 2NaCl.\nSteps:\n1. Balance Cl with 2 NaCl.\n2. Balance Na with 2 Na.\n3. Result: 2Na + Cl2 -> 2NaCl.", "topic": "redox"}
{"answer": "Oxidační činidlo elektrony přijímá a redukuje se; redukční činidlo je odevzdává a oxiduje se.", "choices": null, "id": "che_0202", "kind": "concept", "lang": "cs", "question": "Co je oxidační a redukční činidlo?", "steps": ["Oxidovadlo: příjem elektronů.", "Redukovadlo: výdej elektronů.", "Příklad: Cu2+ a Zn."], "subject": "chemistry", "text": "Answer: Příjemce versus dárce elektronů.\nSteps:\n1. Oxidovadlo: příjem elektronů.\n2. Redukovadlo: výdej elektronů.\n3. Příklad: Cu2+ a Zn.", "topic": "redox"}
{"answer": "The reducing agent is itself oxidized as it donates electrons.", "choices": {"A": "Is reduced", "B": "Stays unchanged", "C": "Is oxidized", "D": "Disappears"}, "id": "che_0203", "kind": "multiple_choice", "lang": "en", "question": "What happens to the reducing agent?", "steps": ["Reducer donates electrons.", "Losing electrons is oxidation.", "Select option C."], "subject": "chemistry", "text": "Answer: Is oxidized.\nSteps:\n1. Reducer donates electrons.\n2. Losing electrons is oxidation.\n3. Select option C.\nAnswer: (C)", "topic": "redox"}
{"answer": "Galvanizing coats iron with zinc, which oxidizes first and shields the steel.", "choices": null, "id": "che_0204", "kind": "concept", "lang": "en", "question": "How does galvanizing prevent rust?", "steps": ["Zinc coats the iron.", "Zinc oxidizes preferentially.", "Iron stays protected."], "subject": "chemistry", "text": "Answer: Zinc sacrifices itself first.\nSteps:\n1. Zinc coats the iron.\n2. Zinc oxidizes preferentially.\n3. Iron stays protected.", "topic": "redox"}
{"answer": "Vyčíslená rovnice je 2Ca + O2 -> 2CaO.", "choices": null, "id": "che_0205", "kind": "worked_example", "lang": "cs", "question": "Vyčísli: Ca + O2 -> CaO.", "steps": ["Kyslík: 2 CaO a 1 O2.", "Vápník: 2 Ca.", "Výsledek: 2Ca + O2 -> 2CaO."], "subject": "chemistry", "text": "Answer: 2Ca + O2 -> 2CaO.\nSteps:\n1. Kyslík: 2 CaO a 1 O2.\n2. Vápník: 2 Ca.\n3. Výsledek: 2Ca + O2 -> 2CaO.", "topic": "redox"}
{"answer": "Hydrogen in metal hydrides is -1 because the metal is less electronegative.", "choices": {"A": "+1", "B": "-1", "C": "0", "D": "+2"}, "id": "che_0206", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of H in NaH?", "steps": ["Na is +1.", "Sum must be 0.", "H = -1; select B."], "subject": "chemistry", "text": "Answer: -1.\nSteps:\n1. Na is +1.\n2. Sum must be 0.\n3. H = -1; select B.\nAnswer: (B)", "topic": "redox"}
{"answer": "Five electrons are gained as manganese drops from +7 to +2.", "choices": null, "id": "che_0207", "kind": "worked_example", "lang": "en", "question": "How many electrons are gained in MnO4- -> Mn2+?", "steps": ["Mn goes +7 to +2.", "Change = 5 units down.", "Electrons gained = 5."], "subject": "chemistry", "text": "Answer: 5 electrons.\nSteps:\n1. Mn goes +7 to +2.\n2. Change = 5 units down.\n3. Electrons gained = 5.", "topic": "redox"}
{"answer": "The first law states energy is conserved: internal energy changes by heat plus work.", "choices": null, "id": "che_0208", "kind": "concept", "lang": "en", "question": "What is the first law of thermodynamics?", "steps": ["Energy cannot be created.", "ΔU = q + w.", "Heat and work interconvert."], "subject": "chemistry", "text": "Answer: Energy is conserved.\nSteps:\n1. Energy cannot be created.\n2. ΔU = q + w.\n3. Heat and work interconvert.", "topic": "thermochemistry"}
{"answer": "Heat entering the system is positive by the chemistry sign convention.", "choices": {"A": "Negative", "B": "Positive", "C": "Zero", "D": "Undefined"}, "id": "che_0209", "kind": "multiple_choice", "lang": "en", "question": "What sign does absorbed heat (q) have?", "steps": ["System gains energy.", "Gain is positive.", "Select option B."], "subject": "chemistry", "text": "Answer: Positive.\nSteps:\n1. System gains energy.\n2. Gain is positive.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "The internal energy change is +300 J, from +500 plus -200 J.", "choices": null, "id": "che_0210", "kind": "worked_example", "lang": "en", "question": "A system absorbs 500 J of heat and does 200 J of work. Find ΔU.", "steps": ["Write: ΔU = q + w.", "Substitute: 500 + (-200).", "ΔU = +300 J."], "subject": "chemistry", "text": "Answer: +300 J.\nSteps:\n1. Write: ΔU = q + w.\n2. Substitute: 500 + (-200).\n3. ΔU = +300 J.", "topic": "thermochemistry"}
{"answer": "Měrná tepelná kapacita je teplo potřebné k ohřátí 1 g látky o 1 °C.", "choices": null, "id": "che_0211", "kind": "concept", "lang": "cs", "question": "Co je měrná tepelná kapacita?", "steps": ["Teplo na gram a stupeň.", "Jednotka J/g°C.", "Voda má 4,184 J/g°C."], "subject": "chemistry", "text": "Answer: Teplo na 1 g a 1 °C.\nSteps:\n1. Teplo na gram a stupeň.\n2. Jednotka J/g°C.\n3. Voda má 4,184 J/g°C.", "topic": "thermochemistry"}
{"answer": "Specific heat is heat capacity per gram of substance.", "choices": {"A": "Per mole only", "B": "Per liter", "C": "Per gram", "D": "Per reaction"}, "id": "che_0212", "kind": "multiple_choice", "lang": "en", "question": "How does specific heat relate to heat capacity?", "steps": ["Heat capacity is total.", "Divide by mass.", "Select option C."], "subject": "chemistry", "text": "Answer: Per gram.\nSteps:\n1. Heat capacity is total.\n2. Divide by mass.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "The aluminum releases 3588 J, from 50 x 0.897 x (-80).", "choices": null, "id": "che_0213", "kind": "worked_example", "lang": "en", "question": "50 g of Al (c = 0.897 J/gC) cools from 100 C to 20 C. Find q.", "steps": ["ΔT = 20 - 100 = -80 C.", "q = 50 x 0.897 x (-80).", "q = -3588 J released."], "subject": "chemistry", "text": "Answer: -3588 J.\nSteps:\n1. ΔT = 20 - 100 = -80 C.\n2. q = 50 x 0.897 x (-80).\n3. q = -3588 J released.", "topic": "thermochemistry"}
{"answer": "Fusion melts solid to liquid and vaporization boils liquid to gas, both absorbing heat.", "choices": null, "id": "che_0214", "kind": "concept", "lang": "en", "question": "What are heats of fusion and vaporization?", "steps": ["Fusion: solid to liquid.", "Vaporization: liquid to gas.", "Both need heat input."], "subject": "chemistry", "text": "Answer: Heats of melting and boiling.\nSteps:\n1. Fusion: solid to liquid.\n2. Vaporization: liquid to gas.\n3. Both need heat input.", "topic": "thermochemistry"}
{"answer": "Melting needs 12.02 kJ, from 2.00 mol times 6.01 kJ/mol.", "choices": null, "id": "che_0215", "kind": "worked_example", "lang": "en", "question": "How much heat melts 36.0 g of ice (ΔHfus = 6.01 kJ/mol)?", "steps": ["Moles = 36.0/18.015 = 2.00.", "Multiply: 2.00 x 6.01.", "Heat = 12.02 kJ."], "subject": "chemistry", "text": "Answer: 12.02 kJ.\nSteps:\n1. Moles = 36.0/18.015 = 2.00.\n2. Multiply: 2.00 x 6.01.\n3. Heat = 12.02 kJ.", "topic": "thermochemistry"}
{"answer": "Vaporization absorbs heat to break liquid bonds, so it is endothermic.", "choices": {"A": "Endothermic", "B": "Exothermic", "C": "Athermal", "D": "Spontaneous only"}, "id": "che_0216", "kind": "multiple_choice", "lang": "en", "question": "Is vaporization endothermic or exothermic?", "steps": ["Bonds break going to gas.", "Breaking needs energy.", "Select option A."], "subject": "chemistry", "text": "Answer: Endothermic.\nSteps:\n1. Bonds break going to gas.\n2. Breaking needs energy.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "K roztátí je třeba 6,01 kJ, protože 18 g je 1 mol a ΔH je 6,01 kJ/mol.", "choices": null, "id": "che_0217", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla roztaví 18 g ledu (ΔH = 6,01 kJ/mol)?", "steps": ["Moly = 18/18 = 1.", "Vynásob: 1 x 6,01.", "Teplo = 6,01 kJ."], "subject": "chemistry", "text": "Answer: 6,01 kJ.\nSteps:\n1. Moly = 18/18 = 1.\n2. Vynásob: 1 x 6,01.\n3. Teplo = 6,01 kJ.", "topic": "thermochemistry"}
{"answer": "Standard enthalpy of formation is ΔH for making one mole from elements in reference states.", "choices": null, "id": "che_0218", "kind": "concept", "lang": "en", "question": "What is standard enthalpy of formation?", "steps": ["Form 1 mol of compound.", "Start from elements.", "Standard states apply."], "subject": "chemistry", "text": "Answer: ΔH to form 1 mol from elements.\nSteps:\n1. Form 1 mol of compound.\n2. Start from elements.\n3. Standard states apply.", "topic": "thermochemistry"}
{"answer": "Elements in reference states have ΔHf of zero by definition.", "choices": {"A": "100 kJ/mol", "B": "0 kJ/mol", "C": "-100 kJ/mol", "D": "Undefined"}, "id": "che_0219", "kind": "multiple_choice", "lang": "en", "question": "What is ΔHf of O2(g)?", "steps": ["O2 is the reference state.", "Reference elements equal zero.", "Select option B."], "subject": "chemistry", "text": "Answer: 0 kJ/mol.\nSteps:\n1. O2 is the reference state.\n2. Reference elements equal zero.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "The combustion ΔH is -890.3 kJ, from -965.1 minus -74.8 kJ.", "choices": null, "id": "che_0220", "kind": "worked_example", "lang": "en", "question": "Use ΔHf: CH4 -74.8, CO2 -393.5, H2O -285.8 kJ/mol. Find ΔH of CH4 + 2O2 -> CO2 + 2H2O.", "steps": ["Products: -393.5 + 2(-285.8) = -965.1.", "Reactants: -74.8 + 0.", "ΔH = -965.1 - (-74.8) = -890.3 kJ."], "subject": "chemistry", "text": "Answer: -890.3 kJ.\nSteps:\n1. Products: -393.5 + 2(-285.8) = -965.1.\n2. Reactants: -74.8 + 0.\n3. ΔH = -965.1 - (-74.8) = -890.3 kJ.", "topic": "thermochemistry"}
{"answer": "Spalné teplo je teplo uvolněné úplným spálením 1 molu látky.", "choices": null, "id": "che_0221", "kind": "concept", "lang": "cs", "question": "Co je spalné teplo?", "steps": ["Úplné spálení v kyslíku.", "Na 1 mol látky.", "Vždy exotermické."], "subject": "chemistry", "text": "Answer: Teplo úplného spálení.\nSteps:\n1. Úplné spálení v kyslíku.\n2. Na 1 mol látky.\n3. Vždy exotermické.", "topic": "thermochemistry"}
{"answer": "Entropy has units of energy per kelvin, joules per kelvin.", "choices": {"A": "kJ/mol", "B": "J/gC", "C": "atm L", "D": "J/K"}, "id": "che_0222", "kind": "multiple_choice", "lang": "en", "question": "What are the units of entropy?", "steps": ["S = q/T.", "Joules over kelvin.", "Select option D."], "subject": "chemistry", "text": "Answer: J/K.\nSteps:\n1. S = q/T.\n2. Joules over kelvin.\n3. Select option D.\nAnswer: (D)", "topic": "thermochemistry"}
{"answer": "The entropy change is 20 J/K, from 6000 J divided by 300 K.", "choices": null, "id": "che_0223", "kind": "worked_example", "lang": "en", "question": "6000 J of heat transfers reversibly at 300 K. Compute ΔS.", "steps": ["Write: ΔS = q/T.", "Substitute: 6000/300.", "ΔS = 20 J/K."], "subject": "chemistry", "text": "Answer: 20 J/K.\nSteps:\n1. Write: ΔS = q/T.\n2. Substitute: 6000/300.\n3. ΔS = 20 J/K.", "topic": "thermochemistry"}
{"answer": "Entropie je míra neuspořádanosti soustavy.", "choices": null, "id": "che_0224", "kind": "concept", "lang": "cs", "question": "Co je entropie?", "steps": ["Míra neuspořádání.", "Plyn má vyšší než pevná látka.", "Roste u samovolných dějů vesmíru."], "subject": "chemistry", "text": "Answer: Míra neuspořádanosti.\nSteps:\n1. Míra neuspořádání.\n2. Plyn má vyšší než pevná látka.\n3. Roste u samovolných dějů vesmíru.", "topic": "thermochemistry"}
{"answer": "Zero ΔG means the system sits at equilibrium with no net drive either way.", "choices": {"A": "Spontaneous", "B": "Nonspontaneous", "C": "At equilibrium", "D": "Impossible"}, "id": "che_0225", "kind": "multiple_choice", "lang": "en", "question": "What does ΔG = 0 mean?", "steps": ["No free energy drive.", "Forward equals reverse.", "Select option C."], "subject": "chemistry", "text": "Answer: At equilibrium.\nSteps:\n1. No free energy drive.\n2. Forward equals reverse.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "The crossover temperature is 500 K, from 50 kJ divided by 0.100 kJ/K.", "choices": null, "id": "che_0226", "kind": "worked_example", "lang": "en", "question": "ΔH = +50 kJ and ΔS = +0.100 kJ/K. Above what T is the reaction spontaneous?", "steps": ["Set ΔG = 0: T = ΔH/ΔS.", "Substitute: 50 / 0.100.", "T = 500 K."], "subject": "chemistry", "text": "Answer: 500 K.\nSteps:\n1. Set ΔG = 0: T = ΔH/ΔS.\n2. Substitute: 50 / 0.100.\n3. T = 500 K.", "topic": "thermochemistry"}
{"answer": "Name branched alkanes by longest chain, lowest numbers, then alphabetical substituents.", "choices": null, "id": "che_0227", "kind": "concept", "lang": "en", "question": "What are the steps for naming branched alkanes?", "steps": ["Find longest chain.", "Number for lowest locants.", "List substituents alphabetically."], "subject": "chemistry", "text": "Answer: Chain, numbers, substituents.\nSteps:\n1. Find longest chain.\n2. Number for lowest locants.\n3. List substituents alphabetically.", "topic": "organic_naming"}
{"answer": "2-methylbutane has five carbons: four in the chain plus one methyl branch.", "choices": {"A": "4", "B": "5", "C": "6", "D": "3"}, "id": "che_0228", "kind": "multiple_choice", "lang": "en", "question": "How many carbons are in 2-methylbutane?", "steps": ["Butane chain = 4.", "Methyl adds 1.", "Total 5; select B."], "subject": "chemistry", "text": "Answer: 5.\nSteps:\n1. Butane chain = 4.\n2. Methyl adds 1.\n3. Total 5; select B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is 3-methylpentane: five carbons with a methyl on carbon 3.", "choices": null, "id": "che_0229", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2CH(CH3)CH2CH3.", "steps": ["Longest chain: 5 = pentane.", "Methyl on carbon 3.", "Name: 3-methylpentane."], "subject": "chemistry", "text": "Answer: 3-methylpentane.\nSteps:\n1. Longest chain: 5 = pentane.\n2. Methyl on carbon 3.\n3. Name: 3-methylpentane.", "topic": "organic_naming"}
{"answer": "Řetězec se čísluje tak, aby substituenty měly co nejnižší čísla.", "choices": null, "id": "che_0230", "kind": "concept", "lang": "cs", "question": "Jak se čísluje uhlíkatý řetězec?", "steps": ["Začni od bližšího konce.", "Substituenty co nejníže.", "Při shodě rozhodne abeceda."], "subject": "chemistry", "text": "Answer: Od konce s nižšími čísly.\nSteps:\n1. Začni od bližšího konce.\n2. Substituenty co nejníže.\n3. Při shodě rozhodne abeceda.", "topic": "organic_naming"}
{"answer": "Ethyne is commonly called acetylene, used in welding torches.", "choices": {"A": "Ethylene", "B": "Ethane", "C": "Benzene", "D": "Acetylene"}, "id": "che_0231", "kind": "multiple_choice", "lang": "en", "question": "What is the common name of ethyne?", "steps": ["Recall C2H2 trivial name.", "Acetylene is standard.", "Select option D."], "subject": "chemistry", "text": "Answer: Acetylene.\nSteps:\n1. Recall C2H2 trivial name.\n2. Acetylene is standard.\n3. Select option D.\nAnswer: (D)", "topic": "organic_naming"}
{"answer": "Cycloalkanes add the cyclo- prefix to the alkane name for the ring size.", "choices": null, "id": "che_0232", "kind": "concept", "lang": "en", "question": "How are cycloalkanes named?", "steps": ["Count ring carbons.", "Add cyclo- prefix.", "Example: cyclohexane."], "subject": "chemistry", "text": "Answer: Cyclo- plus alkane name.\nSteps:\n1. Count ring carbons.\n2. Add cyclo- prefix.\n3. Example: cyclohexane.", "topic": "organic_naming"}
{"answer": "The name is methylbenzene, commonly called toluene.", "choices": null, "id": "che_0233", "kind": "worked_example", "lang": "en", "question": "Name C6H5CH3.", "steps": ["Benzene ring present.", "Methyl substituent attached.", "Name: methylbenzene (toluene)."], "subject": "chemistry", "text": "Answer: Methylbenzene (toluene).\nSteps:\n1. Benzene ring present.\n2. Methyl substituent attached.\n3. Name: methylbenzene (toluene).", "topic": "organic_naming"}
{"answer": "Aldehydes carry a terminal -CHO group and use the -al suffix.", "choices": null, "id": "che_0234", "kind": "concept", "lang": "en", "question": "How are aldehydes named?", "steps": ["Find terminal -CHO.", "Use -al suffix.", "Example: ethanal."], "subject": "chemistry", "text": "Answer: Terminal -CHO with -al.\nSteps:\n1. Find terminal -CHO.\n2. Use -al suffix.\n3. Example: ethanal.", "topic": "organic_naming"}
{"answer": "HCHO is methanal, commonly known as formaldehyde.", "choices": {"A": "Methanal", "B": "Ethanal", "C": "Methanol", "D": "Methane"}, "id": "che_0235", "kind": "multiple_choice", "lang": "en", "question": "What is the IUPAC name of formaldehyde (HCHO)?", "steps": ["One carbon aldehyde.", "Name is methanal.", "Select option A."], "subject": "chemistry", "text": "Answer: Methanal.\nSteps:\n1. One carbon aldehyde.\n2. Name is methanal.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "CH3CH2CHO je propanal.", "choices": null, "id": "che_0236", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH3CH2CHO.", "steps": ["Koncová skupina -CHO.", "Tři uhlíky.", "Název: propanal."], "subject": "chemistry", "text": "Answer: Propanal.\nSteps:\n1. Koncová skupina -CHO.\n2. Tři uhlíky.\n3. Název: propanal.", "topic": "organic_naming"}
{"answer": "Amines are named as alkylamine, with N- prefixes for substituents on nitrogen.", "choices": null, "id": "che_0237", "kind": "concept", "lang": "en", "question": "How are simple amines named?", "steps": ["Name alkyl group.", "Add -amine suffix.", "Example: ethylamine."], "subject": "chemistry", "text": "Answer: Alkyl plus -amine.\nSteps:\n1. Name alkyl group.\n2. Add -amine suffix.\n3. Example: ethylamine.", "topic": "organic_naming"}
{"answer": "CH3NH2 is methylamine: one carbon attached to nitrogen.", "choices": {"A": "Ethylamine", "B": "Methylamine", "C": "Aniline", "D": "Ammonia"}, "id": "che_0238", "kind": "multiple_choice", "lang": "en", "question": "What is the name of CH3NH2?", "steps": ["One-carbon alkyl group.", "Amine suffix applies.", "Select option B."], "subject": "chemistry", "text": "Answer: Methylamine.\nSteps:\n1. One-carbon alkyl group.\n2. Amine suffix applies.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is methoxymethane, commonly dimethyl ether.", "choices": null, "id": "che_0239", "kind": "worked_example", "lang": "en", "question": "Name CH3OCH3.", "steps": ["Oxygen links two carbons.", "Two methyl groups present.", "Name: dimethyl ether."], "subject": "chemistry", "text": "Answer: Dimethyl ether.\nSteps:\n1. Oxygen links two carbons.\n2. Two methyl groups present.\n3. Name: dimethyl ether.", "topic": "organic_naming"}
{"answer": "Ethers have an oxygen bridging two carbon groups, R-O-R.", "choices": null, "id": "che_0240", "kind": "concept", "lang": "en", "question": "What is the ether functional group?", "steps": ["Oxygen between carbons.", "General form R-O-R.", "Example: diethyl ether."], "subject": "chemistry", "text": "Answer: R-O-R linkage.\nSteps:\n1. Oxygen between carbons.\n2. General form R-O-R.\n3. Example: diethyl ether.", "topic": "organic_naming"}
{"answer": "Funkční skupina je atom či skupina určující typické reakce molekuly.", "choices": null, "id": "che_0241", "kind": "concept", "lang": "cs", "question": "Co je funkční skupina?", "steps": ["Reaktivní část molekuly.", "Určuje třídu sloučeniny.", "Příklady: -OH, -COOH, -NH2."], "subject": "chemistry", "text": "Answer: Reaktivní část molekuly.\nSteps:\n1. Reaktivní část molekuly.\n2. Určuje třídu sloučeniny.\n3. Příklady: -OH, -COOH, -NH2.", "topic": "organic_naming"}
{"answer": "The -C triple N group defines a nitrile.", "choices": {"A": "Amine", "B": "Amide", "C": "Nitrile", "D": "Nitro"}, "id": "che_0242", "kind": "multiple_choice", "lang": "en", "question": "Which group is -C≡N?", "steps": ["Triple bond C to N.", "That is a nitrile.", "Select option C."], "subject": "chemistry", "text": "Answer: Nitrile.\nSteps:\n1. Triple bond C to N.\n2. That is a nitrile.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "The name is propanoic acid: three carbons ending in -COOH.", "choices": null, "id": "che_0243", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2COOH.", "steps": ["Count 3 carbons.", "-COOH gives -oic acid.", "Name: propanoic acid."], "subject": "chemistry", "text": "Answer: Propanoic acid.\nSteps:\n1. Count 3 carbons.\n2. -COOH gives -oic acid.\n3. Name: propanoic acid.", "topic": "organic_naming"}
{"answer": "C2H5OH je ethanol.", "choices": null, "id": "che_0244", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu C2H5OH.", "steps": ["Dva uhlíky.", "Skupina -OH = -ol.", "Název: ethanol."], "subject": "chemistry", "text": "Answer: Ethanol.\nSteps:\n1. Dva uhlíky.\n2. Skupina -OH = -ol.\n3. Název: ethanol.", "topic": "organic_naming"}
{"answer": "Common names like acetone persist alongside systematic names like propanone.", "choices": null, "id": "che_0245", "kind": "concept", "lang": "en", "question": "How do common and IUPAC names relate?", "steps": ["IUPAC is systematic.", "Common names are historical.", "Both may be accepted."], "subject": "chemistry", "text": "Answer: Systematic versus historical names.\nSteps:\n1. IUPAC is systematic.\n2. Common names are historical.\n3. Both may be accepted.", "topic": "organic_naming"}
{"answer": "Reaction coordinate diagrams plot energy against progress, showing barriers and intermediates.", "choices": null, "id": "che_0246", "kind": "concept", "lang": "en", "question": "What is a reaction coordinate diagram?", "steps": ["X-axis is progress.", "Y-axis is energy.", "Peaks are transition states."], "subject": "chemistry", "text": "Answer: Energy versus progress plot.\nSteps:\n1. X-axis is progress.\n2. Y-axis is energy.\n3. Peaks are transition states.", "topic": "organic_mechanisms"}
{"answer": "The peak of the energy barrier is the transition state.", "choices": {"A": "Intermediate", "B": "Transition state", "C": "Product", "D": "Reactant"}, "id": "che_0247", "kind": "multiple_choice", "lang": "en", "question": "What is the highest point on an energy diagram?", "steps": ["Peak means max energy.", "That is the transition state.", "Select option B."], "subject": "chemistry", "text": "Answer: Transition state.\nSteps:\n1. Peak means max energy.\n2. That is the transition state.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "The SN2 rate quadruples to 4x because both concentrations double.", "choices": null, "id": "che_0248", "kind": "worked_example", "lang": "en", "question": "SN2 rate = k[RX][Nu]. What happens if both concentrations double?", "steps": ["Write: rate = k x 2[RX] x 2[Nu].", "Factor: 4 x k[RX][Nu].", "Rate becomes 4x."], "subject": "chemistry", "text": "Answer: Rate quadruples.\nSteps:\n1. Write: rate = k x 2[RX] x 2[Nu].\n2. Factor: 4 x k[RX][Nu].\n3. Rate becomes 4x.", "topic": "organic_mechanisms"}
{"answer": "SN2 je jednokroková substituce se současným atakem nukleofilu a odchodem skupiny.", "choices": null, "id": "che_0249", "kind": "concept", "lang": "cs", "question": "Co je substituce SN2?", "steps": ["Jeden krok, zadní atak.", "Rychlost závisí na obou.", "Inverze konfigurace."], "subject": "chemistry", "text": "Answer: Jednokroková substituce.\nSteps:\n1. Jeden krok, zadní atak.\n2. Rychlost závisí na obou.\n3. Inverze konfigurace.", "topic": "organic_mechanisms"}
{"answer": "Good leaving groups are weak bases like iodide that depart with the electron pair.", "choices": null, "id": "che_0250", "kind": "concept", "lang": "en", "question": "What makes a good leaving group?", "steps": ["Must take electron pair.", "Weak bases leave best.", "Order: I- > Br- > Cl- > F-."], "subject": "chemistry", "text": "Answer: Weak base departing with pair.\nSteps:\n1. Must take electron pair.\n2. Weak bases leave best.\n3. Order: I- > Br- > Cl- > F-.", "topic": "organic_mechanisms"}
{"answer": "Iodide leaves fastest as the weakest base among the halides.", "choices": {"A": "F(-)", "B": "Cl(-)", "C": "Br(-)", "D": "I(-)"}, "id": "che_0251", "kind": "multiple_choice", "lang": "en", "question": "Which is the best leaving group?", "steps": ["Weakest base leaves best.", "I- is weakest base.", "Select option D."], "subject": "chemistry", "text": "Answer: I-.\nSteps:\n1. Weakest base leaves best.\n2. I- is weakest base.\n3. Select option D.\nAnswer: (D)", "topic": "organic_mechanisms"}
{"answer": "The major product is 2-butene, the more substituted Zaitsev alkene.", "choices": null, "id": "che_0252", "kind": "worked_example", "lang": "en", "question": "What is the major E2 product of 2-bromobutane with strong base?", "steps": ["Remove H from adjacent carbons.", "Zaitsev favors more substituted alkene.", "Product: 2-butene."], "subject": "chemistry", "text": "Answer: 2-butene.\nSteps:\n1. Remove H from adjacent carbons.\n2. Zaitsev favors more substituted alkene.\n3. Product: 2-butene.", "topic": "organic_mechanisms"}
{"answer": "Zaitsev's rule favors the most substituted alkene in elimination.", "choices": null, "id": "che_0253", "kind": "concept", "lang": "en", "question": "What is Zaitsev's rule?", "steps": ["Elimination removes HX.", "Most substituted alkene wins.", "More stable product forms."], "subject": "chemistry", "text": "Answer: Most substituted alkene favored.\nSteps:\n1. Elimination removes HX.\n2. Most substituted alkene wins.\n3. More stable product forms.", "topic": "organic_mechanisms"}
{"answer": "Eliminace odstraňuje atomy ze sousedních uhlíků za vzniku dvojné vazby.", "choices": null, "id": "che_0254", "kind": "concept", "lang": "cs", "question": "Co je eliminace?", "steps": ["Odchod HX ze sousedů.", "Vzniká alken.", "Opak adice."], "subject": "chemistry", "text": "Answer: Odstranění za vzniku dvojné vazby.\nSteps:\n1. Odchod HX ze sousedů.\n2. Vzniká alken.\n3. Opak adice.", "topic": "organic_mechanisms"}
{"answer": "Markovnikov's rule puts H on the less substituted carbon of the double bond.", "choices": {"A": "H to less substituted C", "B": "H to more substituted C", "C": "Random addition", "D": "No addition occurs"}, "id": "che_0255", "kind": "multiple_choice", "lang": "en", "question": "What does Markovnikov's rule state?", "steps": ["H adds first as electrophile.", "Stable carbocation forms.", "Select option A."], "subject": "chemistry", "text": "Answer: H to less substituted C.\nSteps:\n1. H adds first as electrophile.\n2. Stable carbocation forms.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "Acid-catalyzed hydration of ethene gives ethanol.", "choices": null, "id": "che_0256", "kind": "worked_example", "lang": "en", "question": "What is the product of ethene + H2O with acid catalyst?", "steps": ["H+ adds to double bond.", "Water captures carbocation.", "Product: ethanol."], "subject": "chemistry", "text": "Answer: Ethanol.\nSteps:\n1. H+ adds to double bond.\n2. Water captures carbocation.\n3. Product: ethanol.", "topic": "organic_mechanisms"}
{"answer": "Alkene hydration adds water across the double bond following Markovnikov's rule.", "choices": null, "id": "che_0257", "kind": "concept", "lang": "en", "question": "What is hydration of alkenes?", "steps": ["Water adds to C=C.", "Acid catalyzes it.", "Alcohol forms."], "subject": "chemistry", "text": "Answer: Water addition to alkenes.\nSteps:\n1. Water adds to C=C.\n2. Acid catalyzes it.\n3. Alcohol forms.", "topic": "organic_mechanisms"}
{"answer": "The balanced equation is C2H5OH + 3O2 -> 2CO2 + 3H2O.", "choices": null, "id": "che_0258", "kind": "worked_example", "lang": "en", "question": "Balance ethanol combustion: C2H5OH + O2 -> CO2 + H2O.", "steps": ["Balance C with 2 CO2.", "Balance H with 3 H2O.", "Balance O with 3 O2."], "subject": "chemistry", "text": "Answer: C2H5OH + 3O2 -> 2CO2 + 3H2O.\nSteps:\n1. Balance C with 2 CO2.\n2. Balance H with 3 H2O.\n3. Balance O with 3 O2.", "topic": "organic_mechanisms"}
{"answer": "Tertiary radicals are most stable due to hyperconjugation from three alkyl groups.", "choices": {"A": "Methyl", "B": "Primary", "C": "Tertiary", "D": "Vinyl"}, "id": "che_0259", "kind": "multiple_choice", "lang": "en", "question": "Which carbon radical is most stable?", "steps": ["Alkyl groups stabilize radicals.", "Tertiary has three.", "Select option C."], "subject": "chemistry", "text": "Answer: Tertiary.\nSteps:\n1. Alkyl groups stabilize radicals.\n2. Tertiary has three.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "Hydrogenací propenu vzniká propan.", "choices": null, "id": "che_0260", "kind": "worked_example", "lang": "cs", "question": "Jaký produkt vznikne hydrogenací propenu (H2, Ni)?", "steps": ["Vodík se aduje na dvojnou vazbu.", "Každý uhlík získá vodík.", "Produkt: propan."], "subject": "chemistry", "text": "Answer: Propan.\nSteps:\n1. Vodík se aduje na dvojnou vazbu.\n2. Každý uhlík získá vodík.\n3. Produkt: propan.", "topic": "organic_mechanisms"}
{"answer": "Addition polymerization links alkene monomers into long chains through their double bonds.", "choices": null, "id": "che_0261", "kind": "concept", "lang": "en", "question": "What is addition polymerization?", "steps": ["Monomers have C=C bonds.", "Bonds open and link.", "Chain grows long."], "subject": "chemistry", "text": "Answer: Linking alkenes into chains.\nSteps:\n1. Monomers have C=C bonds.\n2. Bonds open and link.\n3. Chain grows long.", "topic": "organic_mechanisms"}
{"answer": "The repeat unit is -CH2-CH2-, from opened ethene monomers.", "choices": null, "id": "che_0262", "kind": "worked_example", "lang": "en", "question": "What is the repeat unit of polyethene?", "steps": ["Monomer is CH2=CH2.", "Double bond opens.", "Repeat: -CH2-CH2-."], "subject": "chemistry", "text": "Answer: -CH2-CH2-.\nSteps:\n1. Monomer is CH2=CH2.\n2. Double bond opens.\n3. Repeat: -CH2-CH2-.", "topic": "organic_mechanisms"}
{"answer": "The nitronium ion NO2+ is the electrophile in aromatic nitration.", "choices": {"A": "OH(-)", "B": "NO2(+)", "C": "Cl(-)", "D": "NH3"}, "id": "che_0263", "kind": "multiple_choice", "lang": "en", "question": "Which species acts as an electrophile?", "steps": ["Need electron-poor species.", "NO2+ is cationic.", "Select option B."], "subject": "chemistry", "text": "Answer: NO2+.\nSteps:\n1. Need electron-poor species.\n2. NO2+ is cationic.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "Katalyzátor zrychluje reakci snížením aktivační energie a sám se nespotřebuje.", "choices": null, "id": "che_0264", "kind": "concept", "lang": "cs", "question": "Co je katalyzátor?", "steps": ["Alternativní rychlejší cesta.", "Nižší aktivační energie.", "Na konci nezměněn."], "subject": "chemistry", "text": "Answer: Látka zrychlující reakci.\nSteps:\n1. Alternativní rychlejší cesta.\n2. Nižší aktivační energie.\n3. Na konci nezměněn.", "topic": "organic_mechanisms"}
{"answer": "K changes with temperature: heating favors the endothermic direction.", "choices": null, "id": "che_0265", "kind": "concept", "lang": "en", "question": "How does temperature affect K?", "steps": ["K depends on T only.", "Heat favors endothermic side.", "K rises or falls accordingly."], "subject": "chemistry", "text": "Answer: K shifts with temperature.\nSteps:\n1. K depends on T only.\n2. Heat favors endothermic side.\n3. K rises or falls accordingly.", "topic": "equilibrium"}
{"answer": "Only temperature changes K; concentration and pressure only shift position.", "choices": {"A": "Temperature only", "B": "Pressure only", "C": "Concentration only", "D": "Catalysts"}, "id": "che_0266", "kind": "multiple_choice", "lang": "en", "question": "What changes the value of K?", "steps": ["K is temperature-defined.", "Other stresses shift, not change K.", "Select option A."], "subject": "chemistry", "text": "Answer: Temperature only.\nSteps:\n1. K is temperature-defined.\n2. Other stresses shift, not change K.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "The reverse K is 0.25, the reciprocal of 4.", "choices": null, "id": "che_0267", "kind": "worked_example", "lang": "en", "question": "Forward K = 4 for A <-> B. What is K for the reverse?", "steps": ["Reverse inverts the ratio.", "K_rev = 1/K_fwd.", "K_rev = 1/4 = 0.25."], "subject": "chemistry", "text": "Answer: 0.25.\nSteps:\n1. Reverse inverts the ratio.\n2. K_rev = 1/K_fwd.\n3. K_rev = 1/4 = 0.25.", "topic": "equilibrium"}
{"answer": "Dynamická rovnováha znamená stejné rychlosti obou směrů při stálých koncentracích.", "choices": null, "id": "che_0268", "kind": "concept", "lang": "cs", "question": "Co je dynamická rovnováha?", "steps": ["Oba směry běží dál.", "Rychlosti se rovnají.", "Koncentrace se nemění."], "subject": "chemistry", "text": "Answer: Stejné rychlosti obou směrů.\nSteps:\n1. Oba směry běží dál.\n2. Rychlosti se rovnají.\n3. Koncentrace se nemění.", "topic": "equilibrium"}
{"answer": "Doubling all coefficients squares the equilibrium constant.", "choices": {"A": "K halves", "B": "K doubles", "C": "K is squared", "D": "K unchanged"}, "id": "che_0269", "kind": "multiple_choice", "lang": "en", "question": "What happens to K when the equation is doubled?", "steps": ["Exponents double in K.", "That squares the value.", "Select option C."], "subject": "chemistry", "text": "Answer: K is squared.\nSteps:\n1. Exponents double in K.\n2. That squares the value.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "The overall K is 6, from 2 times 3.", "choices": null, "id": "che_0270", "kind": "worked_example", "lang": "en", "question": "Step 1 has K1 = 2 and step 2 has K2 = 3. Find overall K.", "steps": ["Adding steps multiplies K.", "K = K1 x K2.", "K = 2 x 3 = 6."], "subject": "chemistry", "text": "Answer: 6.\nSteps:\n1. Adding steps multiplies K.\n2. K = K1 x K2.\n3. K = 2 x 3 = 6.", "topic": "equilibrium"}
{"answer": "The reaction quotient Q has the K form but uses current, not equilibrium, concentrations.", "choices": null, "id": "che_0271", "kind": "concept", "lang": "en", "question": "What is the reaction quotient Q?", "steps": ["Same form as K.", "Uses current concentrations.", "Compare to K for direction."], "subject": "chemistry", "text": "Answer: Current-state version of K.\nSteps:\n1. Same form as K.\n2. Uses current concentrations.\n3. Compare to K for direction.", "topic": "equilibrium"}
{"answer": "Excess products push the system back toward reactants.", "choices": {"A": "Shifts right", "B": "Shifts left", "C": "No shift", "D": "K changes"}, "id": "che_0272", "kind": "multiple_choice", "lang": "en", "question": "If Q > K, which way does the system shift?", "steps": ["Too many products.", "System consumes them.", "Select option B."], "subject": "chemistry", "text": "Answer: Shifts left.\nSteps:\n1. Too many products.\n2. System consumes them.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "Q is 0.50, from 1.0 divided by (2.0 x 1.0).", "choices": null, "id": "che_0273", "kind": "worked_example", "lang": "en", "question": "For A + B <-> C with [A] = 2.0, [B] = 1.0, [C] = 1.0 M, compute Q.", "steps": ["Write: Q = [C]/([A][B]).", "Substitute: 1.0/(2.0 x 1.0).", "Q = 0.50."], "subject": "chemistry", "text": "Answer: 0.50.\nSteps:\n1. Write: Q = [C]/([A][B]).\n2. Substitute: 1.0/(2.0 x 1.0).\n3. Q = 0.50.", "topic": "equilibrium"}
{"answer": "Odebrání produktu posune rovnováhu doprava, k produktům.", "choices": null, "id": "che_0274", "kind": "worked_example", "lang": "cs", "question": "Kam se posune rovnováha po odebrání produktu?", "steps": ["Produktů je málo.", "Soustava je doplní.", "Posun doprava."], "subject": "chemistry", "text": "Answer: Doprava.\nSteps:\n1. Produktů je málo.\n2. Soustava je doplní.\n3. Posun doprava.", "topic": "equilibrium"}
{"answer": "The system makes more product to replace what was removed.", "choices": {"A": "Shifts right", "B": "Shifts left", "C": "No shift", "D": "Stops reacting"}, "id": "che_0275", "kind": "multiple_choice", "lang": "en", "question": "What happens when a product is removed at equilibrium?", "steps": ["Products are scarce.", "System replaces them.", "Select option A."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Products are scarce.\n2. System replaces them.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "Shrinking volume raises pressure, shifting gas equilibrium toward fewer moles.", "choices": null, "id": "che_0276", "kind": "concept", "lang": "en", "question": "How does decreasing volume affect gas equilibrium?", "steps": ["Smaller volume raises pressure.", "System favors fewer gas moles.", "No effect if moles are equal."], "subject": "chemistry", "text": "Answer: Shifts toward fewer gas moles.\nSteps:\n1. Smaller volume raises pressure.\n2. System favors fewer gas moles.\n3. No effect if moles are equal.", "topic": "equilibrium"}
{"answer": "Higher pressure favors ammonia because 4 gas moles become 2.", "choices": null, "id": "che_0277", "kind": "worked_example", "lang": "en", "question": "For N2 + 3H2 <-> 2NH3, which side does high pressure favor?", "steps": ["Count gas moles: 4 left, 2 right.", "Pressure favors fewer moles.", "High pressure favors NH3."], "subject": "chemistry", "text": "Answer: Products (NH3).\nSteps:\n1. Count gas moles: 4 left, 2 right.\n2. Pressure favors fewer moles.\n3. High pressure favors NH3.", "topic": "equilibrium"}
{"answer": "Inert gas at fixed volume changes no partial pressures, so there is no shift.", "choices": {"A": "Shifts right", "B": "Shifts left", "C": "K doubles", "D": "No shift"}, "id": "che_0278", "kind": "multiple_choice", "lang": "en", "question": "What does adding inert gas at constant volume do?", "steps": ["Partial pressures stay same.", "Q stays equal to K.", "Select option D."], "subject": "chemistry", "text": "Answer: No shift.\nSteps:\n1. Partial pressures stay same.\n2. Q stays equal to K.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "Ksp is the equilibrium constant for a solid dissolving into its ions.", "choices": null, "id": "che_0279", "kind": "concept", "lang": "en", "question": "What is the solubility product Ksp?", "steps": ["Solid salt dissolves to ions.", "Ksp multiplies ion concentrations.", "Larger Ksp means more soluble."], "subject": "chemistry", "text": "Answer: Equilibrium constant of dissolving.\nSteps:\n1. Solid salt dissolves to ions.\n2. Ksp multiplies ion concentrations.\n3. Larger Ksp means more soluble.", "topic": "equilibrium"}
{"answer": "Součin rozpustnosti je rovnovážná konstanta rozpouštění málo rozpustné soli.", "choices": null, "id": "che_0280", "kind": "concept", "lang": "cs", "question": "Co je součin rozpustnosti?", "steps": ["Sůl se rozpouští na ionty.", "Ksp = součin koncentrací.", "Větší Ksp = rozpustnější."], "subject": "chemistry", "text": "Answer: Konstanta rozpouštění soli.\nSteps:\n1. Sůl se rozpouští na ionty.\n2. Ksp = součin koncentrací.\n3. Větší Ksp = rozpustnější.", "topic": "equilibrium"}
{"answer": "Ksp of silver chloride equals [Ag+] times [Cl-].", "choices": {"A": "[AgCl]", "B": "[Ag+][Cl-]", "C": "[Ag+]/[Cl-]", "D": "[Ag+] + [Cl-]"}, "id": "che_0281", "kind": "multiple_choice", "lang": "en", "question": "What is the Ksp expression for AgCl?", "steps": ["AgCl gives Ag+ and Cl-.", "Multiply ion concentrations.", "Select option B."], "subject": "chemistry", "text": "Answer: [Ag+][Cl-].\nSteps:\n1. AgCl gives Ag+ and Cl-.\n2. Multiply ion concentrations.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "The solubility is 1.34 x 10^-5 M, the square root of 1.8 x 10^-10.", "choices": null, "id": "che_0282", "kind": "worked_example", "lang": "en", "question": "AgCl has Ksp = 1.8 x 10^-10. Compute its molar solubility.", "steps": ["Write: s^2 = Ksp.", "Substitute: s = sqrt(1.8 x 10^-10).", "s = 1.34 x 10^-5 M."], "subject": "chemistry", "text": "Answer: 1.34 x 10^-5 M.\nSteps:\n1. Write: s^2 = Ksp.\n2. Substitute: s = sqrt(1.8 x 10^-10).\n3. s = 1.34 x 10^-5 M.", "topic": "equilibrium"}
{"answer": "Cell notation lists anode on the left and cathode on the right, split by a double bar.", "choices": null, "id": "che_0283", "kind": "concept", "lang": "en", "question": "How is galvanic cell notation written?", "steps": ["Anode half on the left.", "Cathode half on the right.", "Double bar is the salt bridge."], "subject": "chemistry", "text": "Answer: Anode || cathode.\nSteps:\n1. Anode half on the left.\n2. Cathode half on the right.\n3. Double bar is the salt bridge.", "topic": "electrochemistry"}
{"answer": "By convention the anode (oxidation) half-cell is written on the left.", "choices": {"A": "Anode", "B": "Cathode", "C": "Salt bridge", "D": "Voltmeter"}, "id": "che_0284", "kind": "multiple_choice", "lang": "en", "question": "Which half-cell goes on the left in cell notation?", "steps": ["Recall anode-left convention.", "Eliminate cathode, bridge, meter.", "Select option A."], "subject": "chemistry", "text": "Answer: Anode.\nSteps:\n1. Recall anode-left convention.\n2. Eliminate cathode, bridge, meter.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "The cell potential is 0.46 V, from 0.80 - 0.34.", "choices": null, "id": "che_0285", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Ag/Cu with E(Ag) = 0.80 V and E(Cu) = 0.34 V.", "steps": ["Cathode is Ag at 0.80 V.", "Anode is Cu at 0.34 V.", "E = 0.80 - 0.34 = 0.46 V."], "subject": "chemistry", "text": "Answer: 0.46 V.\nSteps:\n1. Cathode is Ag at 0.80 V.\n2. Anode is Cu at 0.34 V.\n3. E = 0.80 - 0.34 = 0.46 V.", "topic": "electrochemistry"}
{"answer": "Elektrodový potenciál udává sklon poločlánku redukovat se vůči vodíkové elektrodě.", "choices": null, "id": "che_0286", "kind": "concept", "lang": "cs", "question": "Co je elektrodový potenciál?", "steps": ["Měří se proti vodíku.", "Kladnější = snazší redukce.", "Rozdíl dává napětí článku."], "subject": "chemistry", "text": "Answer: Sklon k redukci proti vodíku.\nSteps:\n1. Měří se proti vodíku.\n2. Kladnější = snazší redukce.\n3. Rozdíl dává napětí článku.", "topic": "electrochemistry"}
{"answer": "A more positive reduction potential means the species reduces more easily.", "choices": {"A": "Harder to reduce", "B": "Easier to reduce", "C": "Never reacts", "D": "Always an anode"}, "id": "che_0287", "kind": "multiple_choice", "lang": "en", "question": "What does a more positive E° mean?", "steps": ["E° ranks reduction ease.", "Higher means easier gain of electrons.", "Select option B."], "subject": "chemistry", "text": "Answer: Easier to reduce.\nSteps:\n1. E° ranks reduction ease.\n2. Higher means easier gain of electrons.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "Positive E° gives negative ΔG, so the cell reaction is spontaneous.", "choices": null, "id": "che_0288", "kind": "worked_example", "lang": "en", "question": "A cell has E° = +0.46 V. Is it spontaneous?", "steps": ["ΔG = -nFE°.", "Positive E° makes ΔG negative.", "Yes, spontaneous."], "subject": "chemistry", "text": "Answer: Yes, spontaneous.\nSteps:\n1. ΔG = -nFE°.\n2. Positive E° makes ΔG negative.\n3. Yes, spontaneous.", "topic": "electrochemistry"}
{"answer": "A concentration cell uses the same electrodes with different ion concentrations to generate voltage.", "choices": null, "id": "che_0289", "kind": "concept", "lang": "en", "question": "What is a concentration cell?", "steps": ["Same metal both sides.", "Different concentrations.", "Voltage evens them out."], "subject": "chemistry", "text": "Answer: Same electrodes, different concentrations.\nSteps:\n1. Same metal both sides.\n2. Different concentrations.\n3. Voltage evens them out.", "topic": "electrochemistry"}
{"answer": "The cell voltage is 0.0592 V, from (0.0592/2) x log(100).", "choices": null, "id": "che_0290", "kind": "worked_example", "lang": "en", "question": "A concentration cell (n = 2) has 1.0 M cathode and 0.010 M anode. Compute E at 25 C.", "steps": ["E° = 0 for same electrodes.", "E = (0.0592/2) x log(1.0/0.010).", "E = 0.0296 x 2 = 0.0592 V."], "subject": "chemistry", "text": "Answer: 0.0592 V.\nSteps:\n1. E° = 0 for same electrodes.\n2. E = (0.0592/2) x log(1.0/0.010).\n3. E = 0.0296 x 2 = 0.0592 V.", "topic": "electrochemistry"}
{"answer": "Series connection adds the individual cell voltages together.", "choices": {"A": "Voltages cancel", "B": "Voltage stays same", "C": "Voltages add", "D": "Current reverses"}, "id": "che_0291", "kind": "multiple_choice", "lang": "en", "question": "What happens wiring batteries in series?", "steps": ["Positive meets negative.", "Potentials sum up.", "Select option C."], "subject": "chemistry", "text": "Answer: Voltages add.\nSteps:\n1. Positive meets negative.\n2. Potentials sum up.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "The lead-acid battery pairs lead and lead dioxide plates in sulfuric acid, rechargeable by reversing the reaction.", "choices": null, "id": "che_0292", "kind": "concept", "lang": "en", "question": "How does a lead-acid battery work?", "steps": ["Pb oxidizes, PbO2 reduces.", "Sulfuric acid is consumed.", "Charging reverses the chemistry."], "subject": "chemistry", "text": "Answer: Pb/PbO2 in sulfuric acid.\nSteps:\n1. Pb oxidizes, PbO2 reduces.\n2. Sulfuric acid is consumed.\n3. Charging reverses the chemistry.", "topic": "electrochemistry"}
{"answer": "Náboj je 600 C, protože 1 A krát 600 s se rovná 600 C.", "choices": null, "id": "che_0293", "kind": "worked_example", "lang": "cs", "question": "Jaký náboj proteče při 1 A za 10 minut?", "steps": ["Převeď čas: 10 min = 600 s.", "Q = I x t = 1 x 600.", "Q = 600 C."], "subject": "chemistry", "text": "Answer: 600 C.\nSteps:\n1. Převeď čas: 10 min = 600 s.\n2. Q = I x t = 1 x 600.\n3. Q = 600 C.", "topic": "electrochemistry"}
{"answer": "There are 0.200 mol of electrons, from 19,300 C divided by 96,485 C/mol.", "choices": null, "id": "che_0294", "kind": "worked_example", "lang": "en", "question": "How many moles of electrons are in 19,300 C?", "steps": ["Write: n = Q / F.", "Substitute: 19,300 / 96,485.", "n = 0.200 mol."], "subject": "chemistry", "text": "Answer: 0.200 mol.\nSteps:\n1. Write: n = Q / F.\n2. Substitute: 19,300 / 96,485.\n3. n = 0.200 mol.", "topic": "electrochemistry"}
{"answer": "The plated object is the cathode, where metal ions are reduced.", "choices": {"A": "Anode", "B": "Cathode", "C": "Salt bridge", "D": "Electrolyte"}, "id": "che_0295", "kind": "multiple_choice", "lang": "en", "question": "In electroplating, what is the object to be plated?", "steps": ["Metal ions must reduce onto it.", "Reduction happens at cathode.", "Select option B."], "subject": "chemistry", "text": "Answer: Cathode.\nSteps:\n1. Metal ions must reduce onto it.\n2. Reduction happens at cathode.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "A sacrificial anode of reactive metal corrodes in place of the protected structure.", "choices": null, "id": "che_0296", "kind": "concept", "lang": "en", "question": "What is a sacrificial anode?", "steps": ["Attach reactive metal.", "It oxidizes preferentially.", "Structure stays intact."], "subject": "chemistry", "text": "Answer: Metal corroding instead of structure.\nSteps:\n1. Attach reactive metal.\n2. It oxidizes preferentially.\n3. Structure stays intact.", "topic": "electrochemistry"}
{"answer": "The plated silver mass is 2.01 g, from 1800 C giving 0.01866 mol Ag.", "choices": null, "id": "che_0297", "kind": "worked_example", "lang": "en", "question": "What mass of Ag plates at 1.00 A for 30.0 min (M = 107.87 g/mol)?", "steps": ["Q = 1.00 x 1800 = 1800 C.", "Mol e- = 1800/96485 = 0.01866 mol Ag.", "Mass = 0.01866 x 107.87 = 2.01 g."], "subject": "chemistry", "text": "Answer: 2.01 g.\nSteps:\n1. Q = 1.00 x 1800 = 1800 C.\n2. Mol e- = 1800/96485 = 0.01866 mol Ag.\n3. Mass = 0.01866 x 107.87 = 2.01 g.", "topic": "electrochemistry"}
{"answer": "Koroze je samovolná oxidace kovů; brání jí nátěry, pozinkování a katodická ochrana.", "choices": null, "id": "che_0298", "kind": "concept", "lang": "cs", "question": "Co je koroze a jak jí bránit?", "steps": ["Oxidace kovu vzduchem a vodou.", "Izoluj povrch nátěrem.", "Obětovaná anoda chrání katodicky."], "subject": "chemistry", "text": "Answer: Oxidace kovů; ochrana izolací a anodou.\nSteps:\n1. Oxidace kovu vzduchem a vodou.\n2. Izoluj povrch nátěrem.\n3. Obětovaná anoda chrání katodicky.", "topic": "electrochemistry"}
{"answer": "Iron rusts only when both oxygen and water are present.", "choices": {"A": "Oxygen alone", "B": "Water alone", "C": "Neither", "D": "Both oxygen and water"}, "id": "che_0299", "kind": "multiple_choice", "lang": "en", "question": "What does iron need to rust?", "steps": ["Dry air gives no rust.", "Air-free water gives no rust.", "Select option D."], "subject": "chemistry", "text": "Answer: Both oxygen and water.\nSteps:\n1. Dry air gives no rust.\n2. Air-free water gives no rust.\n3. Select option D.\nAnswer: (D)", "topic": "electrochemistry"}
{"answer": "The cell potential is 1.10 V, from 212,000 J divided by (2 x 96,485 C).", "choices": null, "id": "che_0300", "kind": "worked_example", "lang": "en", "question": "A cell has ΔG = -212 kJ and n = 2. Compute E° (F = 96485 C/mol).", "steps": ["Write: E° = -ΔG/(nF).", "Substitute: 212,000/(2 x 96,485).", "E° = 1.10 V."], "subject": "chemistry", "text": "Answer: 1.10 V.\nSteps:\n1. Write: E° = -ΔG/(nF).\n2. Substitute: 212,000/(2 x 96,485).\n3. E° = 1.10 V.", "topic": "electrochemistry"}
{"answer": "The law of definite proportions states a compound always has fixed element mass ratios.", "choices": null, "id": "che_0301", "kind": "concept", "lang": "en", "question": "What is the law of definite proportions?", "steps": ["Compounds have fixed formulas.", "Mass ratios stay constant.", "Example: water always 11.2% H."], "subject": "chemistry", "text": "Answer: Fixed mass ratios in compounds.\nSteps:\n1. Compounds have fixed formulas.\n2. Mass ratios stay constant.\n3. Example: water always 11.2% H.", "topic": "stoichiometry"}
{"answer": "Two moles contain 1.204 x 10^24 molecules, double Avogadro's number.", "choices": {"A": "6.022 x 10^23", "B": "3.011 x 10^23", "C": "1.204 x 10^24", "D": "2.408 x 10^24"}, "id": "che_0302", "kind": "multiple_choice", "lang": "en", "question": "How many molecules are in 2.00 mol of O2?", "steps": ["Multiply: 2.00 x 6.022 x 10^23.", "Result 1.204 x 10^24.", "Select option C."], "subject": "chemistry", "text": "Answer: 1.204 x 10^24.\nSteps:\n1. Multiply: 2.00 x 6.022 x 10^23.\n2. Result 1.204 x 10^24.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "There are 1.506 x 10^23 particles, from 0.250 times Avogadro's number.", "choices": null, "id": "che_0303", "kind": "worked_example", "lang": "en", "question": "How many particles are in 0.250 mol of salt?", "steps": ["Write: N = 0.250 x 6.022 x 10^23.", "Multiply: 1.506 x 10^23.", "N = 1.506 x 10^23."], "subject": "chemistry", "text": "Answer: 1.506 x 10^23.\nSteps:\n1. Write: N = 0.250 x 6.022 x 10^23.\n2. Multiply: 1.506 x 10^23.\n3. N = 1.506 x 10^23.", "topic": "stoichiometry"}
{"answer": "Avogadrova konstanta udává počet částic v jednom molu: 6,022 x 10^23.", "choices": null, "id": "che_0304", "kind": "concept", "lang": "cs", "question": "Co je Avogadrova konstanta?", "steps": ["Počet částic na mol.", "Hodnota 6,022 x 10^23.", "Spojí mikro a makro svět."], "subject": "chemistry", "text": "Answer: 6,022 x 10^23 částic/mol.\nSteps:\n1. Počet částic na mol.\n2. Hodnota 6,022 x 10^23.\n3. Spojí mikro a makro svět.", "topic": "stoichiometry"}
{"answer": "The mass is 72.92 g, from 3.00 mol times 24.305 g/mol.", "choices": null, "id": "che_0305", "kind": "worked_example", "lang": "en", "question": "What mass is 3.00 mol of magnesium (M = 24.305 g/mol)?", "steps": ["Write: m = 3.00 x 24.305.", "Multiply.", "m = 72.92 g."], "subject": "chemistry", "text": "Answer: 72.92 g.\nSteps:\n1. Write: m = 3.00 x 24.305.\n2. Multiply.\n3. m = 72.92 g.", "topic": "stoichiometry"}
{"answer": "4 g of H2 is about 2.0 mol, more than any other choice at 1.0 mol.", "choices": {"A": "18 g H2O", "B": "44 g CO2", "C": "4 g H2", "D": "32 g O2"}, "id": "che_0306", "kind": "multiple_choice", "lang": "en", "question": "Which sample contains the most moles?", "steps": ["A: 18/18 = 1.0 mol.", "B: 44/44 = 1.0; D: 32/32 = 1.0.", "C: 4/2 = 2.0; select C."], "subject": "chemistry", "text": "Answer: 4 g H2.\nSteps:\n1. A: 18/18 = 1.0 mol.\n2. B: 44/44 = 1.0; D: 32/32 = 1.0.\n3. C: 4/2 = 2.0; select C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "Theoretical yield is the stoichiometric maximum while actual yield is what is really obtained.", "choices": null, "id": "che_0307", "kind": "concept", "lang": "en", "question": "How do theoretical and actual yield differ?", "steps": ["Theoretical from balanced equation.", "Actual measured in lab.", "Ratio gives percent yield."], "subject": "chemistry", "text": "Answer: Calculated maximum versus measured amount.\nSteps:\n1. Theoretical from balanced equation.\n2. Actual measured in lab.\n3. Ratio gives percent yield.", "topic": "stoichiometry"}
{"answer": "Percent yield is 80%, from 64 g divided by 80 g times 100.", "choices": null, "id": "che_0308", "kind": "worked_example", "lang": "en", "question": "Theoretical yield is 80 g and actual is 64 g. Compute percent yield.", "steps": ["Divide: 64/80 = 0.80.", "Multiply by 100.", "Yield = 80%."], "subject": "chemistry", "text": "Answer: 80%.\nSteps:\n1. Divide: 64/80 = 0.80.\n2. Multiply by 100.\n3. Yield = 80%.", "topic": "stoichiometry"}
{"answer": "Výtěžek je 85 %, protože 85 děleno 100 krát 100 se rovná 85.", "choices": null, "id": "che_0309", "kind": "worked_example", "lang": "cs", "question": "Teoretický výtěžek je 100 g a skutečný 85 g. Vypočítej procentuální výtěžek.", "steps": ["Vyděl: 85/100 = 0,85.", "Vynásob stem.", "Výtěžek = 85 %."], "subject": "chemistry", "text": "Answer: 85 %.\nSteps:\n1. Vyděl: 85/100 = 0,85.\n2. Vynásob stem.\n3. Výtěžek = 85 %.", "topic": "stoichiometry"}
{"answer": "The balanced equation is 4Al + 3O2 -> 2Al2O3.", "choices": {"A": "2, 3, 2", "B": "4, 3, 2", "C": "2, 1, 2", "D": "4, 1, 2"}, "id": "che_0310", "kind": "multiple_choice", "lang": "en", "question": "What coefficients balance Al + O2 -> Al2O3?", "steps": ["Al: 4 left, 2x2 right.", "O: 3x2 left, 2x3 right.", "Select option B."], "subject": "chemistry", "text": "Answer: 4, 3, 2.\nSteps:\n1. Al: 4 left, 2x2 right.\n2. O: 3x2 left, 2x3 right.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Coefficients give the mole ratios for converting between reactants and products.", "choices": null, "id": "che_0311", "kind": "concept", "lang": "en", "question": "What is a mole ratio?", "steps": ["Read coefficients.", "Form ratio of species.", "Convert moles with it."], "subject": "chemistry", "text": "Answer: Coefficient ratio for conversion.\nSteps:\n1. Read coefficients.\n2. Form ratio of species.\n3. Convert moles with it.", "topic": "stoichiometry"}
{"answer": "Four moles of NH3 form, from 6 mol H2 times the 2/3 ratio.", "choices": null, "id": "che_0312", "kind": "worked_example", "lang": "en", "question": "How many moles of NH3 form from 6.0 mol H2 (N2 + 3H2 -> 2NH3)?", "steps": ["Ratio NH3:H2 = 2:3.", "Multiply: 6.0 x 2/3.", "NH3 = 4.0 mol."], "subject": "chemistry", "text": "Answer: 4.0 mol.\nSteps:\n1. Ratio NH3:H2 = 2:3.\n2. Multiply: 6.0 x 2/3.\n3. NH3 = 4.0 mol.", "topic": "stoichiometry"}
{"answer": "The new molarity is 0.40 M, from 2.0 x 100 / 500.", "choices": {"A": "0.40 M", "B": "1.00 M", "C": "2.50 M", "D": "10.0 M"}, "id": "che_0313", "kind": "multiple_choice", "lang": "en", "question": "100 mL of 2.0 M solution dilutes to 500 mL. What is the new M?", "steps": ["Use M1V1 = M2V2.", "M2 = 2.0 x 100/500.", "Select option A."], "subject": "chemistry", "text": "Answer: 0.40 M.\nSteps:\n1. Use M1V1 = M2V2.\n2. M2 = 2.0 x 100/500.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "Ředění snižuje koncentraci přidáním rozpouštědla při stálém množství látky.", "choices": null, "id": "che_0314", "kind": "concept", "lang": "cs", "question": "Co je ředění roztoků?", "steps": ["Moly zůstávají stejné.", "Objem roste.", "Platí M1V1 = M2V2."], "subject": "chemistry", "text": "Answer: Snížení koncentrace rozpouštědlem.\nSteps:\n1. Moly zůstávají stejné.\n2. Objem roste.\n3. Platí M1V1 = M2V2.", "topic": "stoichiometry"}
{"answer": "The needed mass is 14.61 g, from 0.250 mol times 58.44 g/mol.", "choices": null, "id": "che_0315", "kind": "worked_example", "lang": "en", "question": "What mass of NaCl makes 500 mL of 0.500 M solution?", "steps": ["Moles = 0.500 x 0.500 = 0.250.", "Multiply: 0.250 x 58.44.", "Mass = 14.61 g."], "subject": "chemistry", "text": "Answer: 14.61 g.\nSteps:\n1. Moles = 0.500 x 0.500 = 0.250.\n2. Multiply: 0.250 x 58.44.\n3. Mass = 14.61 g.", "topic": "stoichiometry"}
{"answer": "One mole of ideal gas occupies 22.414 L at STP.", "choices": {"A": "1.00 L", "B": "11.2 L", "C": "24.5 L", "D": "22.414 L"}, "id": "che_0316", "kind": "multiple_choice", "lang": "en", "question": "What is the molar volume of gas at STP?", "steps": ["Recall STP value.", "22.414 L per mole.", "Select option D."], "subject": "chemistry", "text": "Answer: 22.414 L.\nSteps:\n1. Recall STP value.\n2. 22.414 L per mole.\n3. Select option D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "The ideal gas law PV = nRT links pressure, volume, moles, and temperature.", "choices": null, "id": "che_0317", "kind": "concept", "lang": "en", "question": "What is the ideal gas law?", "steps": ["Write PV = nRT.", "R = 8.314 J/mol K.", "Assume point particles."], "subject": "chemistry", "text": "Answer: PV = nRT.\nSteps:\n1. Write PV = nRT.\n2. R = 8.314 J/mol K.\n3. Assume point particles.", "topic": "stoichiometry"}
{"answer": "Je to 2,0 molu, protože 44,8 děleno 22,414 se rovná 2,0.", "choices": null, "id": "che_0318", "kind": "worked_example", "lang": "cs", "question": "Kolik molů je ve 44,8 l plynu za STP?", "steps": ["Vyděl molárním objemem.", "44,8 / 22,414.", "n = 2,0 mol."], "subject": "chemistry", "text": "Answer: 2,0 mol.\nSteps:\n1. Vyděl molárním objemem.\n2. 44,8 / 22,414.\n3. n = 2,0 mol.", "topic": "stoichiometry"}
{"answer": "The multiplier is 6, from 180 divided by 30.", "choices": {"A": "3", "B": "6", "C": "2", "D": "12"}, "id": "che_0319", "kind": "multiple_choice", "lang": "en", "question": "Empirical mass is 30 and molecular mass is 180. What is the multiplier?", "steps": ["Divide: 180/30.", "Result = 6.", "Select option B."], "subject": "chemistry", "text": "Answer: 6.\nSteps:\n1. Divide: 180/30.\n2. Result = 6.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Water autoionizes into H+ and OH- with Kw = 1.0 x 10^-14 at 25 C.", "choices": null, "id": "che_0320", "kind": "concept", "lang": "en", "question": "What is the autoionization of water?", "steps": ["H2O gives H+ and OH-.", "Kw = [H+][OH-].", "Kw = 1.0 x 10^-14 at 25 C."], "subject": "chemistry", "text": "Answer: Water splits with Kw = 1e-14.\nSteps:\n1. H2O gives H+ and OH-.\n2. Kw = [H+][OH-].\n3. Kw = 1.0 x 10^-14 at 25 C.", "topic": "acids_bases"}
{"answer": "Pure water has [H+] of 1.0 x 10^-7 M, giving pH 7.", "choices": {"A": "1.0 x 10^-7 M", "B": "1.0 x 10^-14 M", "C": "1.0 M", "D": "0 M"}, "id": "che_0321", "kind": "multiple_choice", "lang": "en", "question": "What is [H+] in pure water at 25 C?", "steps": ["Square root of Kw.", "sqrt(1e-14) = 1e-7.", "Select option A."], "subject": "chemistry", "text": "Answer: 1.0 x 10^-7 M.\nSteps:\n1. Square root of Kw.\n2. sqrt(1e-14) = 1e-7.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "The pH is 2.30, from -log(0.0050).", "choices": null, "id": "che_0322", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.0050 M HCl.", "steps": ["[H+] = 0.0050 M.", "pH = -log(0.0050).", "pH = 2.30."], "subject": "chemistry", "text": "Answer: 2.30.\nSteps:\n1. [H+] = 0.0050 M.\n2. pH = -log(0.0050).\n3. pH = 2.30.", "topic": "acids_bases"}
{"answer": "Autoprotolýza vody je její částečné štěpení na H+ a OH- s Kw = 1 x 10^-14.", "choices": null, "id": "che_0323", "kind": "concept", "lang": "cs", "question": "Co je autoprotolýza vody?", "steps": ["Voda se štěpí na ionty.", "Kw = [H+][OH-].", "Při 25 °C je 1 x 10^-14."], "subject": "chemistry", "text": "Answer: Štěpení vody na ionty.\nSteps:\n1. Voda se štěpí na ionty.\n2. Kw = [H+][OH-].\n3. Při 25 °C je 1 x 10^-14.", "topic": "acids_bases"}
{"answer": "Removing a proton from HCO3- gives carbonate, CO3(2-).", "choices": {"A": "H2CO3", "B": "HCO3(-)", "C": "CO3(2-)", "D": "OH(-)"}, "id": "che_0324", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate base of HCO3-?", "steps": ["Remove one H+.", "Charge drops by one.", "Select option C."], "subject": "chemistry", "text": "Answer: CO3(2-).\nSteps:\n1. Remove one H+.\n2. Charge drops by one.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "The pOH is 1.70, from -log(0.020).", "choices": null, "id": "che_0325", "kind": "worked_example", "lang": "en", "question": "Compute the pOH of 0.020 M NaOH.", "steps": ["[OH-] = 0.020 M.", "pOH = -log(0.020).", "pOH = 1.70."], "subject": "chemistry", "text": "Answer: 1.70.\nSteps:\n1. [OH-] = 0.020 M.\n2. pOH = -log(0.020).\n3. pOH = 1.70.", "topic": "acids_bases"}
{"answer": "Ammonia accepts a proton from water, forming NH4+ and OH- with Kb.", "choices": null, "id": "che_0326", "kind": "concept", "lang": "en", "question": "How does ammonia act as a weak base?", "steps": ["NH3 takes H+ from water.", "NH4+ and OH- form.", "Equilibrium has small Kb."], "subject": "chemistry", "text": "Answer: Takes H+ to make NH4+ and OH-.\nSteps:\n1. NH3 takes H+ from water.\n2. NH4+ and OH- form.\n3. Equilibrium has small Kb.", "topic": "acids_bases"}
{"answer": "The pH is 11.13, from pOH 2.87 via [OH-] = 1.34 x 10^-3 M.", "choices": null, "id": "che_0327", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.10 M NH3 (Kb = 1.8 x 10^-5).", "steps": ["[OH-] = sqrt(1.8 x 10^-5 x 0.10) = 1.34 x 10^-3.", "pOH = 2.87.", "pH = 14 - 2.87 = 11.13."], "subject": "chemistry", "text": "Answer: 11.13.\nSteps:\n1. [OH-] = sqrt(1.8 x 10^-5 x 0.10) = 1.34 x 10^-3.\n2. pOH = 2.87.\n3. pH = 14 - 2.87 = 11.13.", "topic": "acids_bases"}
{"answer": "Ammonium hydrolyzes to release H+, making the solution acidic.", "choices": {"A": "Basic", "B": "Acidic", "C": "Neutral", "D": "Cannot tell"}, "id": "che_0328", "kind": "multiple_choice", "lang": "en", "question": "A 0.10 M NH4Cl solution is what?", "steps": ["NH4+ is acid of weak base.", "It donates H+.", "Select option B."], "subject": "chemistry", "text": "Answer: Acidic.\nSteps:\n1. NH4+ is acid of weak base.\n2. It donates H+.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "pH je 2, protože -log(0,01) = 2.", "choices": null, "id": "che_0329", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,01 M HNO3.", "steps": ["HNO3 disociuje plně.", "pH = -log(0,01).", "pH = 2."], "subject": "chemistry", "text": "Answer: 2.\nSteps:\n1. HNO3 disociuje plně.\n2. pH = -log(0,01).\n3. pH = 2.", "topic": "acids_bases"}
{"answer": "Polyprotic acids lose protons in steps, each with its own smaller Ka.", "choices": null, "id": "che_0330", "kind": "concept", "lang": "en", "question": "How do polyprotic acids dissociate?", "steps": ["First proton easiest.", "Each step has Ka.", "Ka1 > Ka2 > Ka3."], "subject": "chemistry", "text": "Answer: Stepwise with falling Ka.\nSteps:\n1. First proton easiest.\n2. Each step has Ka.\n3. Ka1 > Ka2 > Ka3.", "topic": "acids_bases"}
{"answer": "The first proton of sulfuric acid dissociates fully and strongly.", "choices": {"A": "Strong", "B": "Weak", "C": "Not acidic", "D": "Amphiprotic"}, "id": "che_0331", "kind": "multiple_choice", "lang": "en", "question": "How does the first proton of H2SO4 behave?", "steps": ["First step fully dissociates.", "Only second is weak.", "Select option A."], "subject": "chemistry", "text": "Answer: Strong.\nSteps:\n1. First step fully dissociates.\n2. Only second is weak.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "Exactly 20.0 mL of NaOH is needed, a one-to-one mole match.", "choices": null, "id": "che_0332", "kind": "worked_example", "lang": "en", "question": "What volume of 0.100 M NaOH neutralizes 20.0 mL of 0.100 M HCl?", "steps": ["Moles HCl = 0.0200 x 0.100 = 0.00200.", "Same moles NaOH needed.", "V = 0.00200/0.100 = 20.0 mL."], "subject": "chemistry", "text": "Answer: 20.0 mL.\nSteps:\n1. Moles HCl = 0.0200 x 0.100 = 0.00200.\n2. Same moles NaOH needed.\n3. V = 0.00200/0.100 = 20.0 mL.", "topic": "acids_bases"}
{"answer": "Indicators change color across a narrow pH range near their pKa.", "choices": null, "id": "che_0333", "kind": "concept", "lang": "en", "question": "How do acid-base indicators work?", "steps": ["Weak acid with colored forms.", "Color flips near pKa.", "Range spans ~2 pH units."], "subject": "chemistry", "text": "Answer: Color change near pKa.\nSteps:\n1. Weak acid with colored forms.\n2. Color flips near pKa.\n3. Range spans ~2 pH units.", "topic": "acids_bases"}
{"answer": "Titrace je stanovení koncentrace postupným přidáváním činidla o známé koncentraci.", "choices": null, "id": "che_0334", "kind": "concept", "lang": "cs", "question": "Co je titrace?", "steps": ["Byreta dávkuje titrační činidlo.", "Indikátor ukáže konec.", "Výpočet z ekvivalence."], "subject": "chemistry", "text": "Answer: Stanovení koncentrace titrací.\nSteps:\n1. Byreta dávkuje titrační činidlo.\n2. Indikátor ukáže konec.\n3. Výpočet z ekvivalence.", "topic": "acids_bases"}
{"answer": "Methyl orange is red below pH 3 and yellow above pH 4.4.", "choices": {"A": "Yellow in acid, red in base", "B": "Blue in both", "C": "Colorless in both", "D": "Red in acid, yellow in base"}, "id": "che_0335", "kind": "multiple_choice", "lang": "en", "question": "How does methyl orange change color?", "steps": ["Acid form is red.", "Base form is yellow.", "Select option D."], "subject": "chemistry", "text": "Answer: Red in acid, yellow in base.\nSteps:\n1. Acid form is red.\n2. Base form is yellow.\n3. Select option D.\nAnswer: (D)", "topic": "acids_bases"}
{"answer": "The pH is 2.70, from -log(2.0 x 10^-3).", "choices": null, "id": "che_0336", "kind": "worked_example", "lang": "en", "question": "A solution has [H+] = 2.0 x 10^-3 M. Compute pH.", "steps": ["Write: pH = -log[H+].", "Substitute: -log(2.0 x 10^-3).", "pH = 2.70."], "subject": "chemistry", "text": "Answer: 2.70.\nSteps:\n1. Write: pH = -log[H+].\n2. Substitute: -log(2.0 x 10^-3).\n3. pH = 2.70.", "topic": "acids_bases"}
{"answer": "pOH je 1, protože -log(0,1) = 1.", "choices": null, "id": "che_0337", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pOH roztoku 0,1 M KOH.", "steps": ["KOH disociuje plně.", "pOH = -log(0,1).", "pOH = 1."], "subject": "chemistry", "text": "Answer: 1.\nSteps:\n1. KOH disociuje plně.\n2. pOH = -log(0,1).\n3. pOH = 1.", "topic": "acids_bases"}
{"answer": "Buffers resist pH change by neutralizing small added acid or base.", "choices": {"A": "Fix pH exactly forever", "B": "Resist pH change", "C": "Always give pH 7", "D": "Destroy all ions"}, "id": "che_0338", "kind": "multiple_choice", "lang": "en", "question": "What does a buffer do?", "steps": ["Conjugate pair absorbs H+/OH-.", "pH shifts only slightly.", "Select option B."], "subject": "chemistry", "text": "Answer: Resist pH change.\nSteps:\n1. Conjugate pair absorbs H+/OH-.\n2. pH shifts only slightly.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "Oxygen is -2 except in peroxides (-1) and with fluorine (positive).", "choices": null, "id": "che_0339", "kind": "concept", "lang": "en", "question": "What are the exceptions to oxygen's oxidation state?", "steps": ["Normal rule: O is -2.", "Peroxides: O is -1.", "With F: O is positive."], "subject": "chemistry", "text": "Answer: Peroxides -1, with F positive.\nSteps:\n1. Normal rule: O is -2.\n2. Peroxides: O is -1.\n3. With F: O is positive.", "topic": "redox"}
{"answer": "Each oxygen in hydrogen peroxide is -1, since 2(+1) + 2O = 0.", "choices": {"A": "-2", "B": "-1", "C": "0", "D": "+1"}, "id": "che_0340", "kind": "multiple_choice", "lang": "en", "question": "What is oxygen's oxidation state in H2O2?", "steps": ["H is +1 each.", "Solve: 2 + 2O = 0.", "O = -1; select B."], "subject": "chemistry", "text": "Answer: -1.\nSteps:\n1. H is +1 each.\n2. Solve: 2 + 2O = 0.\n3. O = -1; select B.\nAnswer: (B)", "topic": "redox"}
{"answer": "Phosphorus is +5, since 3(+1) + P + 4(-2) = 0.", "choices": null, "id": "che_0341", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of P in H3PO4.", "steps": ["Assign H +1 and O -2.", "Equation: 3 + P - 8 = 0.", "P = +5."], "subject": "chemistry", "text": "Answer: +5.\nSteps:\n1. Assign H +1 and O -2.\n2. Equation: 3 + P - 8 = 0.\n3. P = +5.", "topic": "redox"}
{"answer": "Disproporcionace je reakce, kde se jeden prvek současně oxiduje i redukuje.", "choices": null, "id": "che_0342", "kind": "concept", "lang": "cs", "question": "Co je disproporcionace?", "steps": ["Jeden prvek, dva osudy.", "Část se oxiduje, část redukuje.", "Příklad: chlor ve vodě."], "subject": "chemistry", "text": "Answer: Současná oxidace i redukce.\nSteps:\n1. Jeden prvek, dva osudy.\n2. Část se oxiduje, část redukuje.\n3. Příklad: chlor ve vodě.", "topic": "redox"}
{"answer": "Copper ions gain electrons to form copper metal, so Cu2+ is reduced.", "choices": {"A": "Zn", "B": "SO4(2-)", "C": "Cu2+", "D": "H+"}, "id": "che_0343", "kind": "multiple_choice", "lang": "en", "question": "In Zn + CuSO4 -> ZnSO4 + Cu, what is reduced?", "steps": ["Cu goes +2 to 0.", "That is a gain of electrons.", "Select option C."], "subject": "chemistry", "text": "Answer: Cu2+.\nSteps:\n1. Cu goes +2 to 0.\n2. That is a gain of electrons.\n3. Select option C.\nAnswer: (C)", "topic": "redox"}
{"answer": "The balanced equation is 2K + Br2 -> 2KBr.", "choices": null, "id": "che_0344", "kind": "worked_example", "lang": "en", "question": "Balance: K + Br2 -> KBr.", "steps": ["Balance Br with 2 KBr.", "Balance K with 2 K.", "Result: 2K + Br2 -> 2KBr."], "subject": "chemistry", "text": "Answer: 2K + Br2 -> 2KBr.\nSteps:\n1. Balance Br with 2 KBr.\n2. Balance K with 2 K.\n3. Result: 2K + Br2 -> 2KBr.", "topic": "redox"}
{"answer": "Half-reactions are scaled to equal electrons, then added with electrons cancelled.", "choices": null, "id": "che_0345", "kind": "concept", "lang": "en", "question": "How are half-reactions combined?", "steps": ["Balance each half.", "Scale to equal electrons.", "Add and cancel electrons."], "subject": "chemistry", "text": "Answer: Scale, add, cancel electrons.\nSteps:\n1. Balance each half.\n2. Scale to equal electrons.\n3. Add and cancel electrons.", "topic": "redox"}
{"answer": "The net ionic equation is Zn + Cu2+ -> Zn2+ + Cu.", "choices": null, "id": "che_0346", "kind": "worked_example", "lang": "en", "question": "Write the net ionic equation for Zn + CuSO4 -> ZnSO4 + Cu.", "steps": ["Split strong electrolytes to ions.", "Cancel spectator SO4(2-).", "Net: Zn + Cu2+ -> Zn2+ + Cu."], "subject": "chemistry", "text": "Answer: Zn + Cu2+ -> Zn2+ + Cu.\nSteps:\n1. Split strong electrolytes to ions.\n2. Cancel spectator SO4(2-).\n3. Net: Zn + Cu2+ -> Zn2+ + Cu.", "topic": "redox"}
{"answer": "Oxygen gains electrons to form MgO, so it is the oxidizing agent.", "choices": {"A": "O2", "B": "Mg", "C": "MgO", "D": "Heat"}, "id": "che_0347", "kind": "multiple_choice", "lang": "en", "question": "In 2Mg + O2 -> 2MgO, what is the oxidizing agent?", "steps": ["Oxygen is reduced.", "Reduced species is the oxidizer.", "Select option A."], "subject": "chemistry", "text": "Answer: O2.\nSteps:\n1. Oxygen is reduced.\n2. Reduced species is the oxidizer.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Dusík má oxidační číslo -3, protože N + 3(+1) = 0.", "choices": null, "id": "che_0348", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo dusíku v NH3.", "steps": ["Přiřaď H +1.", "Rovnice: N + 3 = 0.", "N = -3."], "subject": "chemistry", "text": "Answer: -3.\nSteps:\n1. Přiřaď H +1.\n2. Rovnice: N + 3 = 0.\n3. N = -3.", "topic": "redox"}
{"answer": "Batteries split redox into half-cells so electron flow does electrical work.", "choices": null, "id": "che_0349", "kind": "concept", "lang": "en", "question": "How is redox used in batteries?", "steps": ["Oxidation at one electrode.", "Reduction at the other.", "Electrons flow via wire."], "subject": "chemistry", "text": "Answer: Split halves drive current.\nSteps:\n1. Oxidation at one electrode.\n2. Reduction at the other.\n3. Electrons flow via wire.", "topic": "redox"}
{"answer": "Rusting oxidizes iron metal to iron oxides.", "choices": {"A": "Reduction of Fe", "B": "Sublimation", "C": "Neutralization", "D": "Oxidation of Fe"}, "id": "che_0350", "kind": "multiple_choice", "lang": "en", "question": "What chemical change is rusting?", "steps": ["Fe goes 0 to +3.", "That is oxidation.", "Select option D."], "subject": "chemistry", "text": "Answer: Oxidation of Fe.\nSteps:\n1. Fe goes 0 to +3.\n2. That is oxidation.\n3. Select option D.\nAnswer: (D)", "topic": "redox"}
{"answer": "Two electrons are gained as Cl2 becomes 2Cl-.", "choices": null, "id": "che_0351", "kind": "worked_example", "lang": "en", "question": "How many electrons are gained in Cl2 -> 2Cl-?", "steps": ["Each Cl goes 0 to -1.", "Two Cl gain 1 each.", "Total gained = 2."], "subject": "chemistry", "text": "Answer: 2 electrons.\nSteps:\n1. Each Cl goes 0 to -1.\n2. Two Cl gain 1 each.\n3. Total gained = 2.", "topic": "redox"}
{"answer": "Řada reaktivity řadí kovy podle ochoty oxidovat se.", "choices": null, "id": "che_0352", "kind": "concept", "lang": "cs", "question": "Co je řada reaktivity kovů?", "steps": ["Reaktivnější kov výše.", "Vytěsní méně reaktivní.", "Příklad: Zn vytěsní Cu."], "subject": "chemistry", "text": "Answer: Žebříček reaktivity kovů.\nSteps:\n1. Reaktivnější kov výše.\n2. Vytěsní méně reaktivní.\n3. Příklad: Zn vytěsní Cu.", "topic": "redox"}
{"answer": "Magnesium sits above hydrogen and dissolves in acid with H2 release.", "choices": {"A": "Cu", "B": "Mg", "C": "Pt", "D": "Au"}, "id": "che_0353", "kind": "multiple_choice", "lang": "en", "question": "Which metal releases H2 from dilute acid?", "steps": ["Need metal above H.", "Eliminate Cu, Pt, Au.", "Select option B."], "subject": "chemistry", "text": "Answer: Mg.\nSteps:\n1. Need metal above H.\n2. Eliminate Cu, Pt, Au.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "The balanced equation is 2S + 3O2 -> 2SO3.", "choices": null, "id": "che_0354", "kind": "worked_example", "lang": "en", "question": "Balance: S + O2 -> SO3.", "steps": ["Balance S with 2 SO3 and 2 S.", "Count O: 6 each side.", "Use 3 O2: 2S + 3O2 -> 2SO3."], "subject": "chemistry", "text": "Answer: 2S + 3O2 -> 2SO3.\nSteps:\n1. Balance S with 2 SO3 and 2 S.\n2. Count O: 6 each side.\n3. Use 3 O2: 2S + 3O2 -> 2SO3.", "topic": "redox"}
{"answer": "Vyčíslená rovnice je N2 + 3H2 -> 2NH3.", "choices": null, "id": "che_0355", "kind": "worked_example", "lang": "cs", "question": "Vyčísli: N2 + H2 -> NH3.", "steps": ["Dusík: 2 NH3 a 1 N2.", "Vodík: 3 H2 na 6 H.", "Výsledek: N2 + 3H2 -> 2NH3."], "subject": "chemistry", "text": "Answer: N2 + 3H2 -> 2NH3.\nSteps:\n1. Dusík: 2 NH3 a 1 N2.\n2. Vodík: 3 H2 na 6 H.\n3. Výsledek: N2 + 3H2 -> 2NH3.", "topic": "redox"}
{"answer": "Chromium is +6, since Cr + 4(-2) = -2 gives Cr = +6.", "choices": {"A": "+2", "B": "+4", "C": "+6", "D": "+8"}, "id": "che_0356", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of Cr in CrO4(2-)?", "steps": ["Assign O -2.", "Solve: Cr - 8 = -2.", "Cr = +6; select C."], "subject": "chemistry", "text": "Answer: +6.\nSteps:\n1. Assign O -2.\n2. Solve: Cr - 8 = -2.\n3. Cr = +6; select C.\nAnswer: (C)", "topic": "redox"}
{"answer": "Synthesis joins parts, decomposition splits them, and combustion burns fuel in oxygen.", "choices": null, "id": "che_0357", "kind": "concept", "lang": "en", "question": "How are synthesis, decomposition, and combustion classified?", "steps": ["Synthesis: A + B -> AB.", "Decomposition: AB -> A + B.", "Combustion: fuel + O2."], "subject": "chemistry", "text": "Answer: Joining, splitting, burning.\nSteps:\n1. Synthesis: A + B -> AB.\n2. Decomposition: AB -> A + B.\n3. Combustion: fuel + O2.", "topic": "redox"}
{"answer": "The system is the studied part while everything else is the surroundings.", "choices": null, "id": "che_0358", "kind": "concept", "lang": "en", "question": "What are system and surroundings?", "steps": ["System: reaction studied.", "Surroundings: all else.", "Boundary separates them."], "subject": "chemistry", "text": "Answer: Studied part versus rest.\nSteps:\n1. System: reaction studied.\n2. Surroundings: all else.\n3. Boundary separates them.", "topic": "thermochemistry"}
{"answer": "An isolated system exchanges neither matter nor energy with surroundings.", "choices": {"A": "Both matter and energy", "B": "Energy only", "C": "Neither matter nor energy", "D": "Matter only"}, "id": "che_0359", "kind": "multiple_choice", "lang": "en", "question": "What does an isolated system exchange?", "steps": ["Isolated means fully sealed.", "No matter crosses.", "No energy crosses; select C."], "subject": "chemistry", "text": "Answer: Neither matter nor energy.\nSteps:\n1. Isolated means fully sealed.\n2. No matter crosses.\n3. No energy crosses; select C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "The expansion work is -1000 J, from -100,000 Pa times 0.010 m3.", "choices": null, "id": "che_0360", "kind": "worked_example", "lang": "en", "question": "Gas expands by 0.010 m3 against 100 kPa. Compute the work.", "steps": ["Write: w = -PΔV.", "Substitute: -100,000 x 0.010.", "w = -1000 J."], "subject": "chemistry", "text": "Answer: -1000 J.\nSteps:\n1. Write: w = -PΔV.\n2. Substitute: -100,000 x 0.010.\n3. w = -1000 J.", "topic": "thermochemistry"}
{"answer": "Teplo je přenos energie rozdílem teplot, práce je přenos silou na dráze.", "choices": null, "id": "che_0361", "kind": "concept", "lang": "cs", "question": "Co je teplo a práce?", "steps": ["Teplo teče z teplejšího.", "Práce je síla krát dráha.", "Obě mění energii soustavy."], "subject": "chemistry", "text": "Answer: Dva přenosy energie.\nSteps:\n1. Teplo teče z teplejšího.\n2. Práce je síla krát dráha.\n3. Obě mění energii soustavy.", "topic": "thermochemistry"}
{"answer": "Work done by the system on surroundings is negative.", "choices": {"A": "Positive", "B": "Negative", "C": "Zero", "D": "Undefined"}, "id": "che_0362", "kind": "multiple_choice", "lang": "en", "question": "What sign does work done BY the system have?", "steps": ["System loses energy.", "Loss is negative.", "Select option B."], "subject": "chemistry", "text": "Answer: Negative.\nSteps:\n1. System loses energy.\n2. Loss is negative.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "The heat is 4485 J, from 100 x 0.897 x 50.", "choices": null, "id": "che_0363", "kind": "worked_example", "lang": "en", "question": "How much heat warms 100 g of Al by 50 C (c = 0.897 J/gC)?", "steps": ["Write: q = 100 x 0.897 x 50.", "Multiply.", "q = 4485 J."], "subject": "chemistry", "text": "Answer: 4485 J.\nSteps:\n1. Write: q = 100 x 0.897 x 50.\n2. Multiply.\n3. q = 4485 J.", "topic": "thermochemistry"}
{"answer": "Calorimeter heat capacity links its temperature rise to absorbed heat.", "choices": null, "id": "che_0364", "kind": "concept", "lang": "en", "question": "What is calorimeter heat capacity?", "steps": ["Vessel absorbs some heat.", "Capacity times ΔT gives q.", "Calibrate by burning standard."], "subject": "chemistry", "text": "Answer: Heat per degree of vessel.\nSteps:\n1. Vessel absorbs some heat.\n2. Capacity times ΔT gives q.\n3. Calibrate by burning standard.", "topic": "thermochemistry"}
{"answer": "The heat is 2000 J, from 500 J/C times 4 C.", "choices": null, "id": "che_0365", "kind": "worked_example", "lang": "en", "question": "A calorimeter (C = 500 J/C) warms 4.0 C. How much heat did it absorb?", "steps": ["Write: q = C x ΔT.", "Substitute: 500 x 4.0.", "q = 2000 J."], "subject": "chemistry", "text": "Answer: 2000 J.\nSteps:\n1. Write: q = C x ΔT.\n2. Substitute: 500 x 4.0.\n3. q = 2000 J.", "topic": "thermochemistry"}
{"answer": "A bomb calorimeter holds volume fixed, so it measures internal energy change.", "choices": {"A": "Constant volume", "B": "Constant pressure", "C": "Constant temperature", "D": "Constant mass"}, "id": "che_0366", "kind": "multiple_choice", "lang": "en", "question": "What does a bomb calorimeter hold constant?", "steps": ["Steel bomb is rigid.", "Volume cannot change.", "Select option A."], "subject": "chemistry", "text": "Answer: Constant volume.\nSteps:\n1. Steel bomb is rigid.\n2. Volume cannot change.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "Potřebné teplo je 4184 J, protože 50 x 4,184 x 20 se rovná 4184.", "choices": null, "id": "che_0367", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla ohřeje 50 g vody o 20 °C?", "steps": ["Napiš vzorec: q = 50 x 4,184 x 20.", "Vynásob.", "q = 4184 J."], "subject": "chemistry", "text": "Answer: 4184 J.\nSteps:\n1. Napiš vzorec: q = 50 x 4,184 x 20.\n2. Vynásob.\n3. q = 4184 J.", "topic": "thermochemistry"}
{"answer": "State functions like H, U, S, and G depend only on current state, not path.", "choices": null, "id": "che_0368", "kind": "concept", "lang": "en", "question": "What is a state function?", "steps": ["Depends on state only.", "Path does not matter.", "Examples: H, U, S, G."], "subject": "chemistry", "text": "Answer: Path-independent property.\nSteps:\n1. Depends on state only.\n2. Path does not matter.\n3. Examples: H, U, S, G.", "topic": "thermochemistry"}
{"answer": "Enthalpy change is a state function, unlike path-dependent heat and work.", "choices": {"A": "Heat q", "B": "Work w", "C": "Enthalpy change ΔH", "D": "Path length"}, "id": "che_0369", "kind": "multiple_choice", "lang": "en", "question": "Which is a state function?", "steps": ["q and w depend on path.", "ΔH depends on states.", "Select option C."], "subject": "chemistry", "text": "Answer: Enthalpy change ΔH.\nSteps:\n1. q and w depend on path.\n2. ΔH depends on states.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "The ΔH is -285.8 kJ per mole of water formed.", "choices": null, "id": "che_0370", "kind": "worked_example", "lang": "en", "question": "H2 + 1/2O2 -> H2O has ΔH = -285.8 kJ. How much heat per mole of water?", "steps": ["One mole water forms.", "Heat equals ΔH.", "-285.8 kJ per mole."], "subject": "chemistry", "text": "Answer: -285.8 kJ.\nSteps:\n1. One mole water forms.\n2. Heat equals ΔH.\n3. -285.8 kJ per mole.", "topic": "thermochemistry"}
{"answer": "Kalorimetr je izolovaná nádoba měřící teplo ze změny teploty.", "choices": null, "id": "che_0371", "kind": "concept", "lang": "cs", "question": "Co je kalorimetr?", "steps": ["Izolovaná nádoba.", "Měří změnu teploty.", "Teplo z kapacity a ΔT."], "subject": "chemistry", "text": "Answer: Nádoba na měření tepla.\nSteps:\n1. Izolovaná nádoba.\n2. Měří změnu teploty.\n3. Teplo z kapacity a ΔT.", "topic": "thermochemistry"}
{"answer": "Going from solid to gas raises disorder most, giving positive ΔS.", "choices": {"A": "Gas to solid", "B": "Fewer gas moles", "C": "Liquid to solid", "D": "Solid to gas"}, "id": "che_0372", "kind": "multiple_choice", "lang": "en", "question": "Which change gives positive ΔS?", "steps": ["Disorder must rise.", "Only solid to gas qualifies.", "Select option D."], "subject": "chemistry", "text": "Answer: Solid to gas.\nSteps:\n1. Disorder must rise.\n2. Only solid to gas qualifies.\n3. Select option D.\nAnswer: (D)", "topic": "thermochemistry"}
{"answer": "ΔG is -30 kJ, from -80 minus 500 x (-0.100).", "choices": null, "id": "che_0373", "kind": "worked_example", "lang": "en", "question": "ΔH = -80 kJ and ΔS = -0.100 kJ/K at 500 K. Compute ΔG.", "steps": ["Write: ΔG = -80 - 500 x (-0.100).", "Simplify: -80 + 50.", "ΔG = -30 kJ."], "subject": "chemistry", "text": "Answer: -30 kJ.\nSteps:\n1. Write: ΔG = -80 - 500 x (-0.100).\n2. Simplify: -80 + 50.\n3. ΔG = -30 kJ.", "topic": "thermochemistry"}
{"answer": "Gibbsova energie určuje samovolnost děje: záporná změna znamená samovolný děj.", "choices": null, "id": "che_0374", "kind": "concept", "lang": "cs", "question": "Co je Gibbsova energie?", "steps": ["G = H - TS.", "ΔG < 0 samovolné.", "ΔG = 0 rovnováha."], "subject": "chemistry", "text": "Answer: Energie samovolnosti.\nSteps:\n1. G = H - TS.\n2. ΔG < 0 samovolné.\n3. ΔG = 0 rovnováha.", "topic": "thermochemistry"}
{"answer": "Negative ΔH and positive ΔS make ΔG negative at every temperature.", "choices": {"A": "Always spontaneous", "B": "Never spontaneous", "C": "Only at high T", "D": "Only at low T"}, "id": "che_0375", "kind": "multiple_choice", "lang": "en", "question": "Exothermic with entropy increase is spontaneous when?", "steps": ["ΔG = ΔH - TΔS.", "Both terms negative.", "Select option A."], "subject": "chemistry", "text": "Answer: Always spontaneous.\nSteps:\n1. ΔG = ΔH - TΔS.\n2. Both terms negative.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "Boiling needs 40.7 kJ, from 1.00 mol times 40.7 kJ/mol.", "choices": null, "id": "che_0376", "kind": "worked_example", "lang": "en", "question": "How much heat boils 18.0 g of water (ΔHvap = 40.7 kJ/mol)?", "steps": ["Moles = 18.0/18.015 = 1.00.", "Multiply: 1.00 x 40.7.", "Heat = 40.7 kJ."], "subject": "chemistry", "text": "Answer: 40.7 kJ.\nSteps:\n1. Moles = 18.0/18.015 = 1.00.\n2. Multiply: 1.00 x 40.7.\n3. Heat = 40.7 kJ.", "topic": "thermochemistry"}
{"answer": "Haloalkanes name the halogen as a fluoro-, chloro-, bromo-, or iodo- prefix.", "choices": null, "id": "che_0377", "kind": "concept", "lang": "en", "question": "How are haloalkanes named?", "steps": ["Halogen becomes prefix.", "Number its position.", "Example: 2-bromopropane."], "subject": "chemistry", "text": "Answer: Halogen prefix plus alkane.\nSteps:\n1. Halogen becomes prefix.\n2. Number its position.\n3. Example: 2-bromopropane.", "topic": "organic_naming"}
{"answer": "CH3Cl is chloromethane: one carbon with chlorine.", "choices": {"A": "Chloromethane", "B": "Chloroethane", "C": "Dichloromethane", "D": "Methanol"}, "id": "che_0378", "kind": "multiple_choice", "lang": "en", "question": "What is the name of CH3Cl?", "steps": ["One carbon present.", "Chlorine substituent.", "Select option A."], "subject": "chemistry", "text": "Answer: Chloromethane.\nSteps:\n1. One carbon present.\n2. Chlorine substituent.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "The name is bromoethane: two carbons with bromine.", "choices": null, "id": "che_0379", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2Br.", "steps": ["Count 2 carbons.", "Bromine substituent.", "Name: bromoethane."], "subject": "chemistry", "text": "Answer: Bromoethane.\nSteps:\n1. Count 2 carbons.\n2. Bromine substituent.\n3. Name: bromoethane.", "topic": "organic_naming"}
{"answer": "Halogenalkany se pojmenují předponou fluor-, chlor-, brom- či jod- před alkanem.", "choices": null, "id": "che_0380", "kind": "concept", "lang": "cs", "question": "Jak se pojmenovávají halogenalkany?", "steps": ["Halogen jako předpona.", "Očísluj polohu.", "Příklad: 2-brompropan."], "subject": "chemistry", "text": "Answer: Předpona halogenu + alkan.\nSteps:\n1. Halogen jako předpona.\n2. Očísluj polohu.\n3. Příklad: 2-brompropan.", "topic": "organic_naming"}
{"answer": "Two -OH groups use the -diol suffix with position numbers.", "choices": {"A": "-ol", "B": "-diol", "C": "-al", "D": "-one"}, "id": "che_0381", "kind": "multiple_choice", "lang": "en", "question": "What suffix marks two alcohol groups?", "steps": ["One -OH gives -ol.", "Two give -diol.", "Select option B."], "subject": "chemistry", "text": "Answer: -diol.\nSteps:\n1. One -OH gives -ol.\n2. Two give -diol.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is ethane-1,2-diol: -OH on both carbons.", "choices": null, "id": "che_0382", "kind": "worked_example", "lang": "en", "question": "Name HOCH2CH2OH.", "steps": ["Count 2 carbons.", "-OH on carbons 1 and 2.", "Name: ethane-1,2-diol."], "subject": "chemistry", "text": "Answer: Ethane-1,2-diol.\nSteps:\n1. Count 2 carbons.\n2. -OH on carbons 1 and 2.\n3. Name: ethane-1,2-diol.", "topic": "organic_naming"}
{"answer": "The carboxylic acid group outranks all others and sets the -oic acid suffix.", "choices": null, "id": "che_0383", "kind": "concept", "lang": "en", "question": "Why do carboxylic acids set the suffix?", "steps": ["Highest naming priority.", "Others become prefixes.", "Suffix is -oic acid."], "subject": "chemistry", "text": "Answer: Highest priority group.\nSteps:\n1. Highest naming priority.\n2. Others become prefixes.\n3. Suffix is -oic acid.", "topic": "organic_naming"}
{"answer": "The name is methanoic acid: one carbon with -COOH.", "choices": null, "id": "che_0384", "kind": "worked_example", "lang": "en", "question": "Name HCOOH.", "steps": ["One carbon present.", "-COOH gives -oic acid.", "Name: methanoic acid."], "subject": "chemistry", "text": "Answer: Methanoic acid.\nSteps:\n1. One carbon present.\n2. -COOH gives -oic acid.\n3. Name: methanoic acid.", "topic": "organic_naming"}
{"answer": "Acetic acid is systematically ethanoic acid.", "choices": {"A": "Methanoic acid", "B": "Propanoic acid", "C": "Ethanoic acid", "D": "Butanoic acid"}, "id": "che_0385", "kind": "multiple_choice", "lang": "en", "question": "What is the IUPAC name of acetic acid?", "steps": ["Two carbons present.", "Acid suffix applies.", "Select option C."], "subject": "chemistry", "text": "Answer: Ethanoic acid.\nSteps:\n1. Two carbons present.\n2. Acid suffix applies.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "CH3CHO je ethanal.", "choices": null, "id": "che_0386", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH3CHO.", "steps": ["Koncová skupina -CHO.", "Dva uhlíky.", "Název: ethanal."], "subject": "chemistry", "text": "Answer: Ethanal.\nSteps:\n1. Koncová skupina -CHO.\n2. Dva uhlíky.\n3. Název: ethanal.", "topic": "organic_naming"}
{"answer": "Ketones number the chain to give the carbonyl the lowest locant with -one.", "choices": null, "id": "che_0387", "kind": "concept", "lang": "en", "question": "How are ketones numbered?", "steps": ["Find C=O carbon.", "Number chain lowest there.", "Suffix -one with locant."], "subject": "chemistry", "text": "Answer: Lowest locant for C=O.\nSteps:\n1. Find C=O carbon.\n2. Number chain lowest there.\n3. Suffix -one with locant.", "topic": "organic_naming"}
{"answer": "The carbonyl sits on carbon 2 of four, giving butan-2-one.", "choices": {"A": "Butan-1-one", "B": "Butan-2-one", "C": "Butanal", "D": "Butanoic acid"}, "id": "che_0388", "kind": "multiple_choice", "lang": "en", "question": "What is the name of CH3CH2COCH3?", "steps": ["Four carbons, mid C=O.", "Carbonyl on carbon 2.", "Select option B."], "subject": "chemistry", "text": "Answer: Butan-2-one.\nSteps:\n1. Four carbons, mid C=O.\n2. Carbonyl on carbon 2.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is phenol: -OH attached directly to benzene.", "choices": null, "id": "che_0389", "kind": "worked_example", "lang": "en", "question": "Name C6H5OH.", "steps": ["Benzene ring present.", "-OH on the ring.", "Name: phenol."], "subject": "chemistry", "text": "Answer: Phenol.\nSteps:\n1. Benzene ring present.\n2. -OH on the ring.\n3. Name: phenol.", "topic": "organic_naming"}
{"answer": "Phenols attach -OH directly to an aromatic ring, making them more acidic than alcohols.", "choices": null, "id": "che_0390", "kind": "concept", "lang": "en", "question": "What are phenols?", "steps": ["-OH on aromatic ring.", "Ring stabilizes anion.", "More acidic than alcohols."], "subject": "chemistry", "text": "Answer: -OH on aromatic ring.\nSteps:\n1. -OH on aromatic ring.\n2. Ring stabilizes anion.\n3. More acidic than alcohols.", "topic": "organic_naming"}
{"answer": "Benzenové jádro je šestičlenný aromatický kruh s delokalizovanými elektrony.", "choices": null, "id": "che_0391", "kind": "concept", "lang": "cs", "question": "Co je benzenové jádro?", "steps": ["Šest uhlíků v kruhu.", "Delokalizace elektronů.", "Základ aromatických sloučenin."], "subject": "chemistry", "text": "Answer: Aromatický šestičlenný kruh.\nSteps:\n1. Šest uhlíků v kruhu.\n2. Delokalizace elektronů.\n3. Základ aromatických sloučenin.", "topic": "organic_naming"}
{"answer": "Ortho means adjacent 1,2 positions on a benzene ring.", "choices": {"A": "1,2 positions", "B": "1,3 positions", "C": "1,4 positions", "D": "1,5 positions"}, "id": "che_0392", "kind": "multiple_choice", "lang": "en", "question": "What does ortho- mean on benzene?", "steps": ["Ortho means adjacent.", "That is 1,2.", "Select option A."], "subject": "chemistry", "text": "Answer: 1,2 positions.\nSteps:\n1. Ortho means adjacent.\n2. That is 1,2.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "The name is methyl ethanoate: methyl alcohol part plus ethanoate.", "choices": null, "id": "che_0393", "kind": "worked_example", "lang": "en", "question": "Name CH3COOCH3.", "steps": ["Acid part: ethanoate.", "Alcohol part: methyl.", "Name: methyl ethanoate."], "subject": "chemistry", "text": "Answer: Methyl ethanoate.\nSteps:\n1. Acid part: ethanoate.\n2. Alcohol part: methyl.\n3. Name: methyl ethanoate.", "topic": "organic_naming"}
{"answer": "CH3NH2 je methylamin.", "choices": null, "id": "che_0394", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH3NH2.", "steps": ["Jeden uhlík.", "Skupina -NH2 = amin.", "Název: methylamin."], "subject": "chemistry", "text": "Answer: Methylamin.\nSteps:\n1. Jeden uhlík.\n2. Skupina -NH2 = amin.\n3. Název: methylamin.", "topic": "organic_naming"}
{"answer": "Amides attach -NH2 to a carbonyl and use the -amide suffix.", "choices": null, "id": "che_0395", "kind": "concept", "lang": "en", "question": "How are amides named?", "steps": ["Find C(=O)N group.", "Name chain plus -amide.", "Example: ethanamide."], "subject": "chemistry", "text": "Answer: Chain plus -amide.\nSteps:\n1. Find C(=O)N group.\n2. Name chain plus -amide.\n3. Example: ethanamide.", "topic": "organic_naming"}
{"answer": "SN1 first loses the leaving group to form a carbocation, then the nucleophile attacks.", "choices": null, "id": "che_0396", "kind": "concept", "lang": "en", "question": "What are the SN1 mechanism steps?", "steps": ["Leaving group departs.", "Carbocation forms.", "Nucleophile attacks."], "subject": "chemistry", "text": "Answer: Ionize, then attack.\nSteps:\n1. Leaving group departs.\n2. Carbocation forms.\n3. Nucleophile attacks.", "topic": "organic_mechanisms"}
{"answer": "The SN1 intermediate is a planar carbocation.", "choices": {"A": "Carbocation", "B": "Carbanion", "C": "Radical", "D": "Epoxide"}, "id": "che_0397", "kind": "multiple_choice", "lang": "en", "question": "What intermediate forms in SN1?", "steps": ["Leaving group takes pair.", "Positive carbon remains.", "Select option A."], "subject": "chemistry", "text": "Answer: Carbocation.\nSteps:\n1. Leaving group takes pair.\n2. Positive carbon remains.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "The SN1 rate triples to 3x because rate equals k[RX].", "choices": null, "id": "che_0398", "kind": "worked_example", "lang": "en", "question": "SN1 rate = k[RX]. What happens if [RX] triples?", "steps": ["Write: rate = k x 3[RX].", "Factor: 3 x k[RX].", "Rate becomes 3x."], "subject": "chemistry", "text": "Answer: Rate triples.\nSteps:\n1. Write: rate = k x 3[RX].\n2. Factor: 3 x k[RX].\n3. Rate becomes 3x.", "topic": "organic_mechanisms"}
{"answer": "Přesmyk karbokationu přesune vodík či alkyl na stabilnější uhlík.", "choices": null, "id": "che_0399", "kind": "concept", "lang": "cs", "question": "Co je přesmyk karbokationu?", "steps": ["Nestabilní karbokation.", "Přesun H nebo alkylu.", "Vznikne stabilnější ion."], "subject": "chemistry", "text": "Answer: Přesun na stabilnější uhlík.\nSteps:\n1. Nestabilní karbokation.\n2. Přesun H nebo alkylu.\n3. Vznikne stabilnější ion.", "topic": "organic_mechanisms"}
{"answer": "A hydride shift moves H- to the cationic carbon, relocating the charge.", "choices": null, "id": "che_0400", "kind": "concept", "lang": "en", "question": "What is a hydride shift?", "steps": ["H- migrates to cation.", "Charge moves along.", "More stable cation results."], "subject": "chemistry", "text": "Answer: H- migration to cation.\nSteps:\n1. H- migrates to cation.\n2. Charge moves along.\n3. More stable cation results.", "topic": "organic_mechanisms"}
{"answer": "Tertiary carbocations are most stable through three donating alkyl groups.", "choices": {"A": "Methyl", "B": "Primary", "C": "Tertiary", "D": "Vinyl"}, "id": "che_0401", "kind": "multiple_choice", "lang": "en", "question": "Which carbocation is most stable?", "steps": ["More alkyls mean more stable.", "Tertiary has three.", "Select option C."], "subject": "chemistry", "text": "Answer: Tertiary.\nSteps:\n1. More alkyls mean more stable.\n2. Tertiary has three.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "The product is 2-bromo-2-methylpropane, via the tertiary carbocation.", "choices": null, "id": "che_0402", "kind": "worked_example", "lang": "en", "question": "Predict the HBr addition product of 2-methylpropene.", "steps": ["H adds to CH2 end.", "Tertiary carbocation forms.", "Br captures it: 2-bromo-2-methylpropane."], "subject": "chemistry", "text": "Answer: 2-bromo-2-methylpropane.\nSteps:\n1. H adds to CH2 end.\n2. Tertiary carbocation forms.\n3. Br captures it: 2-bromo-2-methylpropane.", "topic": "organic_mechanisms"}
{"answer": "Regioselectivity is the preference for one positional outcome over others.", "choices": null, "id": "che_0403", "kind": "concept", "lang": "en", "question": "What is regioselectivity?", "steps": ["Multiple positions possible.", "One dominates.", "Example: Markovnikov addition."], "subject": "chemistry", "text": "Answer: Positional preference.\nSteps:\n1. Multiple positions possible.\n2. One dominates.\n3. Example: Markovnikov addition.", "topic": "organic_mechanisms"}
{"answer": "Markovnikovovo pravidlo říká, že vodík se aduje na méně substituovaný uhlík.", "choices": null, "id": "che_0404", "kind": "concept", "lang": "cs", "question": "Co je Markovnikovovo pravidlo?", "steps": ["H na méně substituovaný C.", "Stabilnější karbokation.", "Příklad: propen + HBr."], "subject": "chemistry", "text": "Answer: H na méně substituovaný uhlík.\nSteps:\n1. H na méně substituovaný C.\n2. Stabilnější karbokation.\n3. Příklad: propen + HBr.", "topic": "organic_mechanisms"}
{"answer": "Peroxides trigger radical addition that reverses the usual orientation.", "choices": {"A": "Acid catalyst", "B": "Peroxides", "C": "Low temperature", "D": "Polar solvent"}, "id": "che_0405", "kind": "multiple_choice", "lang": "en", "question": "What causes anti-Markovnikov HBr addition?", "steps": ["Needs radical pathway.", "Peroxides start radicals.", "Select option B."], "subject": "chemistry", "text": "Answer: Peroxides.\nSteps:\n1. Needs radical pathway.\n2. Peroxides start radicals.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "The E1 product is 2-methylpropene, the only possible alkene.", "choices": null, "id": "che_0406", "kind": "worked_example", "lang": "en", "question": "What is the E1 product of tert-butyl bromide with weak base?", "steps": ["Br leaves, tertiary cation forms.", "Base removes a methyl H.", "Product: 2-methylpropene."], "subject": "chemistry", "text": "Answer: 2-methylpropene.\nSteps:\n1. Br leaves, tertiary cation forms.\n2. Base removes a methyl H.\n3. Product: 2-methylpropene.", "topic": "organic_mechanisms"}
{"answer": "E1 is two-step via a carbocation while E2 is one concerted step with base.", "choices": null, "id": "che_0407", "kind": "concept", "lang": "en", "question": "How do E1 and E2 differ?", "steps": ["E1: cation, rate = k[RX].", "E2: concerted, needs strong base.", "E1 with weak base, E2 with strong."], "subject": "chemistry", "text": "Answer: Two-step versus concerted.\nSteps:\n1. E1: cation, rate = k[RX].\n2. E2: concerted, needs strong base.\n3. E1 with weak base, E2 with strong.", "topic": "organic_mechanisms"}
{"answer": "Dehydration of ethanol gives ethene plus water.", "choices": null, "id": "che_0408", "kind": "worked_example", "lang": "en", "question": "What is the product of ethanol dehydration (conc. H2SO4, heat)?", "steps": ["Remove -OH and adjacent H.", "Double bond forms.", "Product: ethene."], "subject": "chemistry", "text": "Answer: Ethene.\nSteps:\n1. Remove -OH and adjacent H.\n2. Double bond forms.\n3. Product: ethene.", "topic": "organic_mechanisms"}
{"answer": "Concentrated sulfuric acid with heat dehydrates alcohols to alkenes.", "choices": {"A": "Dilute NaOH", "B": "Cold water", "C": "H2 with Ni", "D": "Conc. H2SO4, heat"}, "id": "che_0409", "kind": "multiple_choice", "lang": "en", "question": "Which reagent dehydrates alcohols?", "steps": ["Need strong dehydrating acid.", "Conc. H2SO4 with heat works.", "Select option D."], "subject": "chemistry", "text": "Answer: Conc. H2SO4, heat.\nSteps:\n1. Need strong dehydrating acid.\n2. Conc. H2SO4 with heat works.\n3. Select option D.\nAnswer: (D)", "topic": "organic_mechanisms"}
{"answer": "Adicí HCl na ethen vzniká chlorethan.", "choices": null, "id": "che_0410", "kind": "worked_example", "lang": "cs", "question": "Jaký produkt vznikne adicí HCl na ethen?", "steps": ["H se aduje na uhlík.", "Cl na druhý uhlík.", "Produkt: chlorethan."], "subject": "chemistry", "text": "Answer: Chlorethan.\nSteps:\n1. H se aduje na uhlík.\n2. Cl na druhý uhlík.\n3. Produkt: chlorethan.", "topic": "organic_mechanisms"}
{"answer": "Common electrophiles include H+, NO2+, carbocations, and carbonyl carbons.", "choices": null, "id": "che_0411", "kind": "concept", "lang": "en", "question": "What are common electrophiles?", "steps": ["Electron-poor centers.", "Examples: H+, NO2+.", "Carbonyl C also qualifies."], "subject": "chemistry", "text": "Answer: Electron-poor acceptors.\nSteps:\n1. Electron-poor centers.\n2. Examples: H+, NO2+.\n3. Carbonyl C also qualifies.", "topic": "organic_mechanisms"}
{"answer": "Chlorination gives chloromethane plus HCl via a radical chain.", "choices": null, "id": "che_0412", "kind": "worked_example", "lang": "en", "question": "What are the products of methane chlorination (Cl2, light)?", "steps": ["Cl radical abstracts H.", "Methyl radical takes Cl.", "Products: CH3Cl + HCl."], "subject": "chemistry", "text": "Answer: CH3Cl + HCl.\nSteps:\n1. Cl radical abstracts H.\n2. Methyl radical takes Cl.\n3. Products: CH3Cl + HCl.", "topic": "organic_mechanisms"}
{"answer": "UV light splits Cl2 into radicals that start the chain.", "choices": {"A": "UV light", "B": "Darkness", "C": "Water", "D": "Salt"}, "id": "che_0413", "kind": "multiple_choice", "lang": "en", "question": "What initiates methane chlorination?", "steps": ["Need Cl radicals.", "Light splits Cl2.", "Select option A."], "subject": "chemistry", "text": "Answer: UV light.\nSteps:\n1. Need Cl radicals.\n2. Light splits Cl2.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "Radikál je částice s nepárovým elektronem, velmi reaktivní.", "choices": null, "id": "che_0414", "kind": "concept", "lang": "cs", "question": "Co je radikál?", "steps": ["Nepárový elektron.", "Vzniká homolýzou.", "Řetězové reakce."], "subject": "chemistry", "text": "Answer: Částice s nepárovým elektronem.\nSteps:\n1. Nepárový elektron.\n2. Vzniká homolýzou.\n3. Řetězové reakce.", "topic": "organic_mechanisms"}
{"answer": "The law of mass action states reaction rate is proportional to reactant concentration products.", "choices": null, "id": "che_0415", "kind": "concept", "lang": "en", "question": "What is the law of mass action?", "steps": ["Rate scales with concentrations.", "Exponents from stoichiometry.", "Basis of K expressions."], "subject": "chemistry", "text": "Answer: Rate from concentration products.\nSteps:\n1. Rate scales with concentrations.\n2. Exponents from stoichiometry.\n3. Basis of K expressions.", "topic": "equilibrium"}
{"answer": "Pure solids and liquids have constant activity and are left out of K.", "choices": {"A": "Gases", "B": "Solids and liquids", "C": "Ions", "D": "Nothing"}, "id": "che_0416", "kind": "multiple_choice", "lang": "en", "question": "What is omitted from K expressions?", "steps": ["Activities of pure phases are 1.", "Omit solids and liquids.", "Select option B."], "subject": "chemistry", "text": "Answer: Solids and liquids.\nSteps:\n1. Activities of pure phases are 1.\n2. Omit solids and liquids.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "K is 20, from 0.80 divided by 0.20 squared.", "choices": null, "id": "che_0417", "kind": "worked_example", "lang": "en", "question": "For 2A <-> B with [A] = 0.20 M and [B] = 0.80 M, compute K.", "steps": ["Write: K = [B]/[A]^2.", "Substitute: 0.80/(0.20^2) = 0.80/0.04.", "K = 20."], "subject": "chemistry", "text": "Answer: 20.\nSteps:\n1. Write: K = [B]/[A]^2.\n2. Substitute: 0.80/(0.20^2) = 0.80/0.04.\n3. K = 20.", "topic": "equilibrium"}
{"answer": "Zákon působení hmoty říká, že rychlost závisí na součinu koncentrací reaktantů.", "choices": null, "id": "che_0418", "kind": "concept", "lang": "cs", "question": "Co je zákon působení hmoty?", "steps": ["Rychlost ze součinu koncentrací.", "Exponenty ze stechiometrie.", "Základ pro K."], "subject": "chemistry", "text": "Answer: Rychlost ze součinu koncentrací.\nSteps:\n1. Rychlost ze součinu koncentrací.\n2. Exponenty ze stechiometrie.\n3. Základ pro K.", "topic": "equilibrium"}
{"answer": "A tiny K means reactants dominate at equilibrium.", "choices": {"A": "Reactants dominate", "B": "Products dominate", "C": "No equilibrium", "D": "K is zero"}, "id": "che_0419", "kind": "multiple_choice", "lang": "en", "question": "What does a very small K mean?", "steps": ["K = products/reactants.", "Small K favors denominator.", "Select option A."], "subject": "chemistry", "text": "Answer: Reactants dominate.\nSteps:\n1. K = products/reactants.\n2. Small K favors denominator.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "The system is already at equilibrium because Q equals K.", "choices": null, "id": "che_0420", "kind": "worked_example", "lang": "en", "question": "Q = 5 and K = 5. Which way does the system shift?", "steps": ["Compare: Q = K.", "No excess either side.", "No shift; at equilibrium."], "subject": "chemistry", "text": "Answer: No shift.\nSteps:\n1. Compare: Q = K.\n2. No excess either side.\n3. No shift; at equilibrium.", "topic": "equilibrium"}
{"answer": "Adding a species shifts equilibrium away; removing one shifts toward it.", "choices": null, "id": "che_0421", "kind": "concept", "lang": "en", "question": "How do concentration changes shift equilibrium?", "steps": ["Add reactant: shift right.", "Remove product: shift right.", "Reverse for opposite changes."], "subject": "chemistry", "text": "Answer: Away from added species.\nSteps:\n1. Add reactant: shift right.\n2. Remove product: shift right.\n3. Reverse for opposite changes.", "topic": "equilibrium"}
{"answer": "Extra reactant is consumed by shifting toward products.", "choices": {"A": "Shifts left", "B": "No shift", "C": "Shifts right", "D": "K changes"}, "id": "che_0422", "kind": "multiple_choice", "lang": "en", "question": "Adding more reactant shifts equilibrium where?", "steps": ["Reactants in excess.", "System consumes them.", "Select option C."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Reactants in excess.\n2. System consumes them.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "High pressure and low temperature favor ammonia: fewer moles and exothermic reaction.", "choices": null, "id": "che_0423", "kind": "worked_example", "lang": "en", "question": "Which conditions favor NH3 in N2 + 3H2 <-> 2NH3 (exothermic)?", "steps": ["Fewer gas moles right: high P.", "Exothermic: low T.", "High P plus low T favor NH3."], "subject": "chemistry", "text": "Answer: High pressure, low temperature.\nSteps:\n1. Fewer gas moles right: high P.\n2. Exothermic: low T.\n3. High P plus low T favor NH3.", "topic": "equilibrium"}
{"answer": "Ochlazení exotermické rovnováhy ji posune k produktům.", "choices": null, "id": "che_0424", "kind": "worked_example", "lang": "cs", "question": "Kam posune ochlazení exotermickou rovnováhu?", "steps": ["Teplo je produkt.", "Odebrání tepla.", "Posun k produktům."], "subject": "chemistry", "text": "Answer: K produktům.\nSteps:\n1. Teplo je produkt.\n2. Odebrání tepla.\n3. Posun k produktům.", "topic": "equilibrium"}
{"answer": "Removing heat from an exothermic reaction pulls it toward products.", "choices": {"A": "Shifts right", "B": "Shifts left", "C": "No shift", "D": "K becomes 1"}, "id": "che_0425", "kind": "multiple_choice", "lang": "en", "question": "Cooling an exothermic reaction shifts it which way?", "steps": ["Heat is a product.", "Removing product shifts right.", "Select option A."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Heat is a product.\n2. Removing product shifts right.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "Heterogeneous equilibria mix phases, and K includes only gases and dissolved species.", "choices": null, "id": "che_0426", "kind": "concept", "lang": "en", "question": "How is K written for heterogeneous equilibria?", "steps": ["Include gases.", "Include aqueous ions.", "Omit pure solids, liquids."], "subject": "chemistry", "text": "Answer: Gases and ions only.\nSteps:\n1. Include gases.\n2. Include aqueous ions.\n3. Omit pure solids, liquids.", "topic": "equilibrium"}
{"answer": "K equals [CO2] = 0.050, since solids are omitted.", "choices": null, "id": "che_0427", "kind": "worked_example", "lang": "en", "question": "For CaCO3(s) <-> CaO(s) + CO2(g) with [CO2] = 0.050 M, find K.", "steps": ["Write: K = [CO2].", "Omit both solids.", "K = 0.050."], "subject": "chemistry", "text": "Answer: 0.050.\nSteps:\n1. Write: K = [CO2].\n2. Omit both solids.\n3. K = 0.050.", "topic": "equilibrium"}
{"answer": "With no mole change, the RT term vanishes and Kp equals Kc.", "choices": {"A": "Δn = 1", "B": "Δn = 0", "C": "Δn = -1", "D": "Never"}, "id": "che_0428", "kind": "multiple_choice", "lang": "en", "question": "When does Kp equal Kc?", "steps": ["Kp = Kc(RT)^Δn.", "Need exponent zero.", "Select option B."], "subject": "chemistry", "text": "Answer: Δn = 0.\nSteps:\n1. Kp = Kc(RT)^Δn.\n2. Need exponent zero.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "Δn is -2, from 2 product moles minus 4 reactant moles.", "choices": null, "id": "che_0429", "kind": "worked_example", "lang": "en", "question": "Compute Δn(gas) for N2 + 3H2 <-> 2NH3.", "steps": ["Products: 2 moles.", "Reactants: 1 + 3 = 4.", "Δn = 2 - 4 = -2."], "subject": "chemistry", "text": "Answer: -2.\nSteps:\n1. Products: 2 moles.\n2. Reactants: 1 + 3 = 4.\n3. Δn = 2 - 4 = -2.", "topic": "equilibrium"}
{"answer": "Heterogenní rovnováha zahrnuje více skupenství, například pevnou látku a plyn.", "choices": null, "id": "che_0430", "kind": "concept", "lang": "cs", "question": "Co je heterogenní rovnováha?", "steps": ["Více fází najednou.", "Pevné látky se vynechávají z K.", "Příklad: CaCO3 <-> CaO + CO2."], "subject": "chemistry", "text": "Answer: Rovnováha více fází.\nSteps:\n1. Více fází najednou.\n2. Pevné látky se vynechávají z K.\n3. Příklad: CaCO3 <-> CaO + CO2.", "topic": "equilibrium"}
{"answer": "Catalysts speed both directions equally, leaving K unchanged.", "choices": {"A": "K doubles", "B": "K halves", "C": "K becomes 1", "D": "K unchanged"}, "id": "che_0431", "kind": "multiple_choice", "lang": "en", "question": "What does a catalyst do to K?", "steps": ["Both rates rise equally.", "Ratio stays same.", "Select option D."], "subject": "chemistry", "text": "Answer: K unchanged.\nSteps:\n1. Both rates rise equally.\n2. Ratio stays same.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "The solubility is 1.21 x 10^-3 M, from (7.1 x 10^-9 / 4)^(1/3).", "choices": null, "id": "che_0432", "kind": "worked_example", "lang": "en", "question": "PbI2 has Ksp = 7.1 x 10^-9. Compute its molar solubility.", "steps": ["Write: Ksp = 4s^3.", "s^3 = 7.1 x 10^-9 / 4 = 1.775 x 10^-9.", "s = 1.21 x 10^-3 M."], "subject": "chemistry", "text": "Answer: 1.21 x 10^-3 M.\nSteps:\n1. Write: Ksp = 4s^3.\n2. s^3 = 7.1 x 10^-9 / 4 = 1.775 x 10^-9.\n3. s = 1.21 x 10^-3 M.", "topic": "equilibrium"}
{"answer": "Each half-cell pairs an electrode with its ion solution for one half-reaction.", "choices": null, "id": "che_0433", "kind": "concept", "lang": "en", "question": "What is a half-cell?", "steps": ["Electrode plus solution.", "Hosts one half-reaction.", "Two halves make a cell."], "subject": "chemistry", "text": "Answer: Electrode plus half-reaction.\nSteps:\n1. Electrode plus solution.\n2. Hosts one half-reaction.\n3. Two halves make a cell.", "topic": "electrochemistry"}
{"answer": "Reduction gains electrons at the cathode, remembered as RED CAT.", "choices": {"A": "Anode", "B": "Cathode", "C": "Salt bridge", "D": "Wire"}, "id": "che_0434", "kind": "multiple_choice", "lang": "en", "question": "Where does reduction occur?", "steps": ["Recall RED CAT mnemonic.", "Cathode gains electrons.", "Select option B."], "subject": "chemistry", "text": "Answer: Cathode.\nSteps:\n1. Recall RED CAT mnemonic.\n2. Cathode gains electrons.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "The cell potential is 1.61 V, from -0.76 - (-2.37).", "choices": null, "id": "che_0435", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Mg/Zn with E(Mg) = -2.37 V and E(Zn) = -0.76 V.", "steps": ["Cathode is Zn at -0.76 V.", "Anode is Mg at -2.37 V.", "E = -0.76 - (-2.37) = 1.61 V."], "subject": "chemistry", "text": "Answer: 1.61 V.\nSteps:\n1. Cathode is Zn at -0.76 V.\n2. Anode is Mg at -2.37 V.\n3. E = -0.76 - (-2.37) = 1.61 V.", "topic": "electrochemistry"}
{"answer": "Anoda je elektroda, kde probíhá oxidace; katoda, kde probíhá redukce.", "choices": null, "id": "che_0436", "kind": "concept", "lang": "cs", "question": "Co je anoda a katoda?", "steps": ["Anoda: oxidace.", "Katoda: redukce.", "Pomůcka: AN OX, RED KAT."], "subject": "chemistry", "text": "Answer: Oxidace versus redukce.\nSteps:\n1. Anoda: oxidace.\n2. Katoda: redukce.\n3. Pomůcka: AN OX, RED KAT.", "topic": "electrochemistry"}
{"answer": "In a galvanic cell the anode is negative as it releases electrons.", "choices": {"A": "Negative", "B": "Positive", "C": "Neutral", "D": "Grounded"}, "id": "che_0437", "kind": "multiple_choice", "lang": "en", "question": "What is the anode's sign in a galvanic cell?", "steps": ["Anode emits electrons.", "It becomes negative.", "Select option A."], "subject": "chemistry", "text": "Answer: Negative.\nSteps:\n1. Anode emits electrons.\n2. It becomes negative.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "Standard potentials use 1 M ions, 1 atm gases, and 25 C.", "choices": null, "id": "che_0438", "kind": "concept", "lang": "en", "question": "What are standard conditions for E°?", "steps": ["Ions at 1 M.", "Gases at 1 atm.", "Temperature 25 C."], "subject": "chemistry", "text": "Answer: 1 M, 1 atm, 25 C.\nSteps:\n1. Ions at 1 M.\n2. Gases at 1 atm.\n3. Temperature 25 C.", "topic": "electrochemistry"}
{"answer": "ΔG is -77.2 kJ, from -1 x 96485 x 0.80 J.", "choices": null, "id": "che_0439", "kind": "worked_example", "lang": "en", "question": "Compute ΔG for n = 1 and E = 0.80 V (F = 96485 C/mol).", "steps": ["Write: ΔG = -1 x 96485 x 0.80.", "Multiply: -77,188 J.", "ΔG = -77.2 kJ."], "subject": "chemistry", "text": "Answer: -77.2 kJ.\nSteps:\n1. Write: ΔG = -1 x 96485 x 0.80.\n2. Multiply: -77,188 J.\n3. ΔG = -77.2 kJ.", "topic": "electrochemistry"}
{"answer": "The potential is 0.68 V, from 0.80 - 0.0592 x log(100).", "choices": null, "id": "che_0440", "kind": "worked_example", "lang": "en", "question": "E° = 0.80 V, n = 1, Q = 100 at 25 C. Compute E.", "steps": ["Write: E = 0.80 - 0.0592 x log(100).", "log(100) = 2.", "E = 0.80 - 0.118 = 0.68 V."], "subject": "chemistry", "text": "Answer: 0.68 V.\nSteps:\n1. Write: E = 0.80 - 0.0592 x log(100).\n2. log(100) = 2.\n3. E = 0.80 - 0.118 = 0.68 V.", "topic": "electrochemistry"}
{"answer": "At 25 C the Nernst slope is 0.0592 V per decade per electron.", "choices": {"A": "0.0257 V", "B": "0.0592 mV", "C": "0.0592 V", "D": "1.00 V"}, "id": "che_0441", "kind": "multiple_choice", "lang": "en", "question": "What is the Nernst slope at 25 C?", "steps": ["2.303 RT/F at 298 K.", "Equals 0.0592 V.", "Select option C."], "subject": "chemistry", "text": "Answer: 0.0592 V.\nSteps:\n1. 2.303 RT/F at 298 K.\n2. Equals 0.0592 V.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "Water electrolysis gives hydrogen at the cathode and oxygen at the anode.", "choices": null, "id": "che_0442", "kind": "concept", "lang": "en", "question": "What are the products of water electrolysis?", "steps": ["Cathode reduces H+ to H2.", "Anode oxidizes water to O2.", "Ratio H2:O2 is 2:1."], "subject": "chemistry", "text": "Answer: H2 and O2.\nSteps:\n1. Cathode reduces H+ to H2.\n2. Anode oxidizes water to O2.\n3. Ratio H2:O2 is 2:1.", "topic": "electrochemistry"}
{"answer": "Vzniknou 2,02 g vodíku, protože 2 moly elektronů dají 1 mol H2.", "choices": null, "id": "che_0443", "kind": "worked_example", "lang": "cs", "question": "Kolik vodíku vznikne ze 2 molů elektronů při elektrolýze?", "steps": ["2 e- dají 1 H2.", "Moly H2 = 1.", "Hmotnost = 1 x 2,016 = 2,02 g."], "subject": "chemistry", "text": "Answer: 2,02 g.\nSteps:\n1. 2 e- dají 1 H2.\n2. Moly H2 = 1.\n3. Hmotnost = 1 x 2,016 = 2,02 g.", "topic": "electrochemistry"}
{"answer": "The hydrogen volume is 11.2 L, from 0.50 mol times 22.414 L/mol.", "choices": null, "id": "che_0444", "kind": "worked_example", "lang": "en", "question": "What volume of H2 at STP comes from 1.00 mol of electrons?", "steps": ["2 e- give 1 H2: 0.50 mol.", "Multiply: 0.50 x 22.414.", "V = 11.2 L."], "subject": "chemistry", "text": "Answer: 11.2 L.\nSteps:\n1. 2 e- give 1 H2: 0.50 mol.\n2. Multiply: 0.50 x 22.414.\n3. V = 11.2 L.", "topic": "electrochemistry"}
{"answer": "Chloride oxidizes to chlorine gas at the anode of brine electrolysis.", "choices": {"A": "O2", "B": "H2", "C": "Na", "D": "Cl2"}, "id": "che_0445", "kind": "multiple_choice", "lang": "en", "question": "What forms at the anode in brine electrolysis?", "steps": ["Cl- oxidizes.", "Product is Cl2 gas.", "Select option D."], "subject": "chemistry", "text": "Answer: Cl2.\nSteps:\n1. Cl- oxidizes.\n2. Product is Cl2 gas.\n3. Select option D.\nAnswer: (D)", "topic": "electrochemistry"}
{"answer": "The dry cell pairs a zinc anode with a carbon cathode in ammonium chloride paste.", "choices": null, "id": "che_0446", "kind": "concept", "lang": "en", "question": "How does a dry cell work?", "steps": ["Zn can is the anode.", "Carbon rod is cathode.", "Paste electrolyte conducts."], "subject": "chemistry", "text": "Answer: Zn anode, carbon cathode.\nSteps:\n1. Zn can is the anode.\n2. Carbon rod is cathode.\n3. Paste electrolyte conducts.", "topic": "electrochemistry"}
{"answer": "The current is 13.4 A, from 48,243 C divided by 3600 s.", "choices": null, "id": "che_0447", "kind": "worked_example", "lang": "en", "question": "What current passes 0.500 mol of electrons in 1.00 hour?", "steps": ["Q = 0.500 x 96485 = 48,243 C.", "t = 3600 s.", "I = 48,243/3600 = 13.4 A."], "subject": "chemistry", "text": "Answer: 13.4 A.\nSteps:\n1. Q = 0.500 x 96485 = 48,243 C.\n2. t = 3600 s.\n3. I = 48,243/3600 = 13.4 A.", "topic": "electrochemistry"}
{"answer": "Akumulátor je dobíjecí článek, jehož reakci lze proudem obrátit.", "choices": null, "id": "che_0448", "kind": "concept", "lang": "cs", "question": "Co je akumulátor?", "steps": ["Galvanický článek.", "Reakce je vratná.", "Nabíjení ji obrátí."], "subject": "chemistry", "text": "Answer: Dobíjecí článek.\nSteps:\n1. Galvanický článek.\n2. Reakce je vratná.\n3. Nabíjení ji obrátí.", "topic": "electrochemistry"}
{"answer": "The lead-acid cell is rechargeable by driving current backward.", "choices": {"A": "Leclanché dry cell", "B": "Lead-acid cell", "C": "Daniell cell", "D": "Concentration cell"}, "id": "che_0449", "kind": "multiple_choice", "lang": "en", "question": "Which cell is rechargeable?", "steps": ["Need reversible chemistry.", "Lead-acid reverses.", "Select option B."], "subject": "chemistry", "text": "Answer: Lead-acid cell.\nSteps:\n1. Need reversible chemistry.\n2. Lead-acid reverses.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "The time is 32.2 min, from 9,649 C divided by 5.00 A.", "choices": null, "id": "che_0450", "kind": "worked_example", "lang": "en", "question": "How long at 5.00 A to pass 0.100 mol of electrons?", "steps": ["Q = 0.100 x 96485 = 9,649 C.", "t = 9,649/5.00 = 1,930 s.", "t = 32.2 min."], "subject": "chemistry", "text": "Answer: 32.2 min.\nSteps:\n1. Q = 0.100 x 96485 = 9,649 C.\n2. t = 9,649/5.00 = 1,930 s.\n3. t = 32.2 min.", "topic": "electrochemistry"}
{"answer": "The law of conservation of mass states matter is neither created nor destroyed in reactions.", "choices": null, "id": "che_0451", "kind": "concept", "lang": "en", "question": "What is the law of conservation of mass?", "steps": ["Atoms rearrange only.", "Total mass stays fixed.", "Basis of balancing."], "subject": "chemistry", "text": "Answer: Mass is conserved in reactions.\nSteps:\n1. Atoms rearrange only.\n2. Total mass stays fixed.\n3. Basis of balancing.", "topic": "stoichiometry"}
{"answer": "One mole of helium holds 6.022 x 10^23 atoms.", "choices": {"A": "6.022 x 10^23", "B": "1.204 x 10^24", "C": "3.011 x 10^23", "D": "1.00 x 10^23"}, "id": "che_0452", "kind": "multiple_choice", "lang": "en", "question": "How many atoms are in 1.00 mol of helium?", "steps": ["One mole means Avogadro's count.", "Value 6.022 x 10^23.", "Select option A."], "subject": "chemistry", "text": "Answer: 6.022 x 10^23.\nSteps:\n1. One mole means Avogadro's count.\n2. Value 6.022 x 10^23.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "The mass is 19.70 g, from 0.100 mol times 196.97 g/mol.", "choices": null, "id": "che_0453", "kind": "worked_example", "lang": "en", "question": "What mass is 0.100 mol of gold (M = 196.97 g/mol)?", "steps": ["Write: m = 0.100 x 196.97.", "Multiply.", "m = 19.70 g."], "subject": "chemistry", "text": "Answer: 19.70 g.\nSteps:\n1. Write: m = 0.100 x 196.97.\n2. Multiply.\n3. m = 19.70 g.", "topic": "stoichiometry"}
{"answer": "Relativní atomová hmotnost je průměrná hmotnost atomu vůči 1/12 uhlíku 12.", "choices": null, "id": "che_0454", "kind": "concept", "lang": "cs", "question": "Co je relativní atomová hmotnost?", "steps": ["Průměr přes izotopy.", "Jednotka 1/12 12C.", "Bezrozměrné číslo."], "subject": "chemistry", "text": "Answer: Průměrná hmotnost atomu.\nSteps:\n1. Průměr přes izotopy.\n2. Jednotka 1/12 12C.\n3. Bezrozměrné číslo.", "topic": "stoichiometry"}
{"answer": "There are 2.00 mol, from 8.00 g divided by 4.003 g/mol.", "choices": null, "id": "che_0455", "kind": "worked_example", "lang": "en", "question": "How many moles are in 8.00 g of helium (M = 4.003 g/mol)?", "steps": ["Write: n = 8.00/4.003.", "Divide.", "n = 2.00 mol."], "subject": "chemistry", "text": "Answer: 2.00 mol.\nSteps:\n1. Write: n = 8.00/4.003.\n2. Divide.\n3. n = 2.00 mol.", "topic": "stoichiometry"}
{"answer": "Sulfuric acid totals 98.08 g/mol from 2 H, 1 S, and 4 O.", "choices": {"A": "49.04 g/mol", "B": "98.08 g/mol", "C": "114.08 g/mol", "D": "82.08 g/mol"}, "id": "che_0456", "kind": "multiple_choice", "lang": "en", "question": "What is the molar mass of H2SO4?", "steps": ["2x1.008 + 32.06 + 4x16.00.", "Total 98.08.", "Select option B."], "subject": "chemistry", "text": "Answer: 98.08 g/mol.\nSteps:\n1. 2x1.008 + 32.06 + 4x16.00.\n2. Total 98.08.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Formula mass is per formula unit in amu while molar mass is per mole in g/mol.", "choices": null, "id": "che_0457", "kind": "concept", "lang": "en", "question": "How do formula mass and molar mass differ?", "steps": ["Formula mass: one unit, amu.", "Molar mass: one mole, g/mol.", "Numerically equal."], "subject": "chemistry", "text": "Answer: Per unit versus per mole.\nSteps:\n1. Formula mass: one unit, amu.\n2. Molar mass: one mole, g/mol.\n3. Numerically equal.", "topic": "stoichiometry"}
{"answer": "The mass is 150.1 g, from 1.50 mol times 100.09 g/mol.", "choices": null, "id": "che_0458", "kind": "worked_example", "lang": "en", "question": "What mass is 1.50 mol of CaCO3 (M = 100.09 g/mol)?", "steps": ["Write: m = 1.50 x 100.09.", "Multiply.", "m = 150.1 g."], "subject": "chemistry", "text": "Answer: 150.1 g.\nSteps:\n1. Write: m = 1.50 x 100.09.\n2. Multiply.\n3. m = 150.1 g.", "topic": "stoichiometry"}
{"answer": "Je to 0,50 molu, protože 20 děleno 40,08 se rovná 0,50.", "choices": null, "id": "che_0459", "kind": "worked_example", "lang": "cs", "question": "Kolik molů je ve 20 g vápníku (M = 40,08 g/mol)?", "steps": ["Napiš vzorec: n = 20/40,08.", "Vyděl.", "n = 0,50 mol."], "subject": "chemistry", "text": "Answer: 0,50 mol.\nSteps:\n1. Napiš vzorec: n = 20/40,08.\n2. Vyděl.\n3. n = 0,50 mol.", "topic": "stoichiometry"}
{"answer": "The balanced equation is C3H8 + 5O2 -> 3CO2 + 4H2O.", "choices": {"A": "1, 3, 3, 4", "B": "2, 5, 3, 4", "C": "1, 5, 3, 4", "D": "1, 5, 4, 3"}, "id": "che_0460", "kind": "multiple_choice", "lang": "en", "question": "What coefficients balance C3H8 + O2 -> CO2 + H2O?", "steps": ["C: 3 CO2. H: 4 H2O.", "O: 5 O2.", "Select option C."], "subject": "chemistry", "text": "Answer: 1, 5, 3, 4.\nSteps:\n1. C: 3 CO2. H: 4 H2O.\n2. O: 5 O2.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "The stoichiometric map routes mass to moles, across the ratio, then back to mass.", "choices": null, "id": "che_0461", "kind": "concept", "lang": "en", "question": "What is the stoichiometric map?", "steps": ["Mass to moles via M.", "Moles across via ratio.", "Moles to mass via M."], "subject": "chemistry", "text": "Answer: Mass-mole-mole-mass route.\nSteps:\n1. Mass to moles via M.\n2. Moles across via ratio.\n3. Mole to mass via M.", "topic": "stoichiometry"}
{"answer": "Three moles of H2 are needed, from 2 mol NH3 times the 3/2 ratio.", "choices": null, "id": "che_0462", "kind": "worked_example", "lang": "en", "question": "How much H2 is needed to make 2.0 mol NH3 (N2 + 3H2 -> 2NH3)?", "steps": ["Ratio H2:NH3 = 3:2.", "Multiply: 2.0 x 3/2.", "H2 = 3.0 mol."], "subject": "chemistry", "text": "Answer: 3.0 mol.\nSteps:\n1. Ratio H2:NH3 = 3:2.\n2. Multiply: 2.0 x 3/2.\n3. H2 = 3.0 mol.", "topic": "stoichiometry"}
{"answer": "Hydrogen limits because 3 mol H2 pairs with only 1 mol N2, leaving N2 over.", "choices": {"A": "H2 limits", "B": "N2 limits", "C": "Neither limits", "D": "Both limit"}, "id": "che_0463", "kind": "multiple_choice", "lang": "en", "question": "With 3 mol N2 and 3 mol H2 for N2 + 3H2 -> 2NH3, what limits?", "steps": ["3 H2 needs 1 N2.", "N2 is in excess.", "Select option A."], "subject": "chemistry", "text": "Answer: H2 limits.\nSteps:\n1. 3 H2 needs 1 N2.\n2. N2 is in excess.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "Nadbytek reaktantu je množství zbývající po spotřebování limitujícího reaktantu.", "choices": null, "id": "che_0464", "kind": "concept", "lang": "cs", "question": "Co je nadbytek reaktantu?", "steps": ["Více, než reakce spotřebuje.", "Zbude po reakci.", "Opak limitujícího reaktantu."], "subject": "chemistry", "text": "Answer: Nespotřebovaný zbytek.\nSteps:\n1. Více, než reakce spotřebuje.\n2. Zbude po reakci.\n3. Opak limitujícího reaktantu.", "topic": "stoichiometry"}
{"answer": "Excess N2 left is 0.333 mol, from 1.00 minus 0.667 mol consumed.", "choices": null, "id": "che_0465", "kind": "worked_example", "lang": "en", "question": "1.00 mol N2 reacts with 2.00 mol H2 (N2 + 3H2 -> 2NH3). How much N2 remains?", "steps": ["H2 limits: needs 2.00/3 = 0.667 N2.", "Subtract: 1.00 - 0.667.", "N2 left = 0.333 mol."], "subject": "chemistry", "text": "Answer: 0.333 mol.\nSteps:\n1. H2 limits: needs 2.00/3 = 0.667 N2.\n2. Subtract: 1.00 - 0.667.\n3. N2 left = 0.333 mol.", "topic": "stoichiometry"}
{"answer": "The molarity is 0.40 M, from 0.200 mol divided by 0.500 L.", "choices": {"A": "0.10 M", "B": "0.40 M", "C": "1.00 M", "D": "2.50 M"}, "id": "che_0466", "kind": "multiple_choice", "lang": "en", "question": "What is the molarity of 0.200 mol in 0.500 L?", "steps": ["Write: M = 0.200/0.500.", "Divide: 0.40.", "Select option B."], "subject": "chemistry", "text": "Answer: 0.40 M.\nSteps:\n1. Write: M = 0.200/0.500.\n2. Divide: 0.40.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "The volume is 0.200 L, from 0.100 mol divided by 0.500 M.", "choices": null, "id": "che_0467", "kind": "worked_example", "lang": "en", "question": "What volume of 0.500 M solution holds 0.100 mol?", "steps": ["Write: V = n/M.", "Substitute: 0.100/0.500.", "V = 0.200 L."], "subject": "chemistry", "text": "Answer: 0.200 L.\nSteps:\n1. Write: V = n/M.\n2. Substitute: 0.100/0.500.\n3. V = 0.200 L.", "topic": "stoichiometry"}
{"answer": "Koncentrace je 0,2 M, protože 0,3 děleno 1,5 se rovná 0,2.", "choices": null, "id": "che_0468", "kind": "worked_example", "lang": "cs", "question": "Jaká je koncentrace 0,3 molu v 1,5 l?", "steps": ["Napiš vzorec: M = 0,3/1,5.", "Vyděl.", "M = 0,2 mol/l."], "subject": "chemistry", "text": "Answer: 0,2 M.\nSteps:\n1. Napiš vzorec: M = 0,3/1,5.\n2. Vyděl.\n3. M = 0,2 mol/l.", "topic": "stoichiometry"}
{"answer": "The volume is 67.2 L, from 3.00 mol times 22.414 L/mol.", "choices": {"A": "22.4 L", "B": "44.8 L", "C": "33.6 L", "D": "67.2 L"}, "id": "che_0469", "kind": "multiple_choice", "lang": "en", "question": "What volume does 3.00 mol of gas occupy at STP?", "steps": ["Multiply: 3.00 x 22.414.", "Result 67.2 L.", "Select option D."], "subject": "chemistry", "text": "Answer: 67.2 L.\nSteps:\n1. Multiply: 3.00 x 22.414.\n2. Result 67.2 L.\n3. Select option D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "Arrhenius acids release H+ and bases release OH- in water.", "choices": null, "id": "che_0470", "kind": "concept", "lang": "en", "question": "What is the Arrhenius definition?", "steps": ["Acid gives H+ in water.", "Base gives OH- in water.", "Limited to aqueous solutions."], "subject": "chemistry", "text": "Answer: H+ versus OH- in water.\nSteps:\n1. Acid gives H+ in water.\n2. Base gives OH- in water.\n3. Limited to aqueous solutions.", "topic": "acids_bases"}
{"answer": "An Arrhenius base yields hydroxide ions in water.", "choices": {"A": "H+", "B": "Electrons", "C": "OH-", "D": "Salts"}, "id": "che_0471", "kind": "multiple_choice", "lang": "en", "question": "What does an Arrhenius base produce in water?", "steps": ["Recall OH- release.", "Eliminate H+, electrons, salts.", "Select option C."], "subject": "chemistry", "text": "Answer: OH-.\nSteps:\n1. Recall OH- release.\n2. Eliminate H+, electrons, salts.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "The pH is 3.70, from -log(2.0 x 10^-4).", "choices": null, "id": "che_0472", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 2.0 x 10^-4 M HCl.", "steps": ["[H+] = 2.0 x 10^-4 M.", "pH = -log(2.0 x 10^-4).", "pH = 3.70."], "subject": "chemistry", "text": "Answer: 3.70.\nSteps:\n1. [H+] = 2.0 x 10^-4 M.\n2. pH = -log(2.0 x 10^-4).\n3. pH = 3.70.", "topic": "acids_bases"}
{"answer": "Arrheniova kyselina uvolňuje ve vodě ionty H+.", "choices": null, "id": "che_0473", "kind": "concept", "lang": "cs", "question": "Co je Arrheniova kyselina?", "steps": ["Uvolňuje H+ ve vodě.", "Příklad: HCl.", "Platí jen ve vodném prostředí."], "subject": "chemistry", "text": "Answer: Zdroj H+ ve vodě.\nSteps:\n1. Uvolňuje H+ ve vodě.\n2. Příklad: HCl.\n3. Platí jen ve vodném prostředí.", "topic": "acids_bases"}
{"answer": "Hydrofluoric acid ionizes only partly, so it is weak.", "choices": {"A": "HCl", "B": "HF", "C": "HNO3", "D": "HBr"}, "id": "che_0474", "kind": "multiple_choice", "lang": "en", "question": "Which of these is a weak acid?", "steps": ["Strong: HCl, HNO3, HBr.", "HF is famously weak.", "Select option B."], "subject": "chemistry", "text": "Answer: HF.\nSteps:\n1. Strong: HCl, HNO3, HBr.\n2. HF is famously weak.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "Percent ionization is dissociated acid over initial concentration times 100.", "choices": null, "id": "che_0475", "kind": "concept", "lang": "en", "question": "What is percent ionization?", "steps": ["Divide [H+] by initial C.", "Multiply by 100.", "Higher means stronger acid."], "subject": "chemistry", "text": "Answer: Share of acid dissociated.\nSteps:\n1. Divide [H+] by initial C.\n2. Multiply by 100.\n3. Higher means stronger acid.", "topic": "acids_bases"}
{"answer": "Percent ionization is 1.34%, from 1.34 x 10^-3 divided by 0.10.", "choices": null, "id": "che_0476", "kind": "worked_example", "lang": "en", "question": "0.10 M acetic acid gives [H+] = 1.34 x 10^-3 M. Compute percent ionization.", "steps": ["Divide: 1.34 x 10^-3 / 0.10 = 0.0134.", "Multiply by 100.", "Ionization = 1.34%."], "subject": "chemistry", "text": "Answer: 1.34%.\nSteps:\n1. Divide: 1.34 x 10^-3 / 0.10 = 0.0134.\n2. Multiply by 100.\n3. Ionization = 1.34%.", "topic": "acids_bases"}
{"answer": "The first dissociation dominates pH because later Ka values are tiny.", "choices": null, "id": "che_0477", "kind": "concept", "lang": "en", "question": "Why does the first step dominate polyprotic pH?", "steps": ["Ka1 far exceeds Ka2.", "First H+ dwarfs the rest.", "Approximate with Ka1 only."], "subject": "chemistry", "text": "Answer: Ka1 dwarfs later steps.\nSteps:\n1. Ka1 far exceeds Ka2.\n2. First H+ dwarfs the rest.\n3. Approximate with Ka1 only.", "topic": "acids_bases"}
{"answer": "Ka2 of carbonic acid is far smaller than Ka1, so the second proton is very weak.", "choices": {"A": "Large", "B": "Equal to Ka1", "C": "Strong", "D": "Much smaller than Ka1"}, "id": "che_0478", "kind": "multiple_choice", "lang": "en", "question": "How does Ka2 of H2CO3 compare to Ka1?", "steps": ["Second proton harder to lose.", "Ka2 << Ka1.", "Select option D."], "subject": "chemistry", "text": "Answer: Much smaller than Ka1.\nSteps:\n1. Second proton harder to lose.\n2. Ka2 << Ka1.\n3. Select option D.\nAnswer: (D)", "topic": "acids_bases"}
{"answer": "pH je 1,70, protože -log(0,02) = 1,70.", "choices": null, "id": "che_0479", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,02 M HCl.", "steps": ["HCl disociuje plně.", "pH = -log(0,02).", "pH = 1,70."], "subject": "chemistry", "text": "Answer: 1,70.\nSteps:\n1. HCl disociuje plně.\n2. pH = -log(0,02).\n3. pH = 1,70.", "topic": "acids_bases"}
{"answer": "The leveling effect caps acid strength in water at H3O+.", "choices": null, "id": "che_0480", "kind": "concept", "lang": "en", "question": "What is the leveling effect of water?", "steps": ["Strong acids protonate water.", "All become H3O+.", "No stronger acid survives."], "subject": "chemistry", "text": "Answer: Water caps strength at H3O+.\nSteps:\n1. Strong acids protonate water.\n2. All become H3O+.\n3. No stronger acid survives.", "topic": "acids_bases"}
{"answer": "Hydronium is the strongest acid that can exist in water.", "choices": {"A": "H3O+", "B": "HCl", "C": "H2SO4", "D": "CH3COOH"}, "id": "che_0481", "kind": "multiple_choice", "lang": "en", "question": "What is the strongest acid in water?", "steps": ["Stronger acids level to H3O+.", "H3O+ is the cap.", "Select option A."], "subject": "chemistry", "text": "Answer: H3O+.\nSteps:\n1. Stronger acids level to H3O+.\n2. H3O+ is the cap.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "The base-to-acid ratio is 10:1, since log(ratio) = 5.76 - 4.76 = 1.", "choices": null, "id": "che_0482", "kind": "worked_example", "lang": "en", "question": "An acetate buffer (pKa = 4.76) has pH 5.76. Find the base/acid ratio.", "steps": ["Write: 5.76 = 4.76 + log(ratio).", "log(ratio) = 1.", "Ratio = 10:1."], "subject": "chemistry", "text": "Answer: 10:1.\nSteps:\n1. Write: 5.76 = 4.76 + log(ratio).\n2. log(ratio) = 1.\n3. Ratio = 10:1.", "topic": "acids_bases"}
{"answer": "Buffer capacity is the amount of acid or base a buffer absorbs before pH shifts sharply.", "choices": null, "id": "che_0483", "kind": "concept", "lang": "en", "question": "What is buffer capacity?", "steps": ["Depends on concentrations.", "Higher means tougher buffer.", "Exhausted when a partner runs out."], "subject": "chemistry", "text": "Answer: Absorbable acid/base amount.\nSteps:\n1. Depends on concentrations.\n2. Higher means tougher buffer.\n3. Exhausted when a partner runs out.", "topic": "acids_bases"}
{"answer": "Disociační konstanta Ka vyjadřuje sílu kyseliny v rovnováze.", "choices": null, "id": "che_0484", "kind": "concept", "lang": "cs", "question": "Co je disociační konstanta?", "steps": ["Rovnováha disociace.", "Větší Ka = silnější kyselina.", "pKa = -log Ka."], "subject": "chemistry", "text": "Answer: Konstanta síly kyseliny.\nSteps:\n1. Rovnováha disociace.\n2. Větší Ka = silnější kyselina.\n3. pKa = -log Ka.", "topic": "acids_bases"}
{"answer": "Back-titration handles slow or insoluble analytes by reacting excess reagent first.", "choices": {"A": "Strong-strong only", "B": "Slow or insoluble analytes", "C": "Gases only", "D": "Never used"}, "id": "che_0485", "kind": "multiple_choice", "lang": "en", "question": "When is back-titration used?", "steps": ["Direct endpoint unclear.", "Excess reagent added first.", "Select option B."], "subject": "chemistry", "text": "Answer: Slow or insoluble analytes.\nSteps:\n1. Direct endpoint unclear.\n2. Excess reagent added first.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "There are 7.50 mmol, from 15.0 mL times 0.500 M.", "choices": null, "id": "che_0486", "kind": "worked_example", "lang": "en", "question": "How many millimoles are in 15.0 mL of 0.500 M base?", "steps": ["Write: mmol = 15.0 x 0.500.", "Multiply.", "mmol = 7.50."], "subject": "chemistry", "text": "Answer: 7.50 mmol.\nSteps:\n1. Write: mmol = 15.0 x 0.500.\n2. Multiply.\n3. mmol = 7.50.", "topic": "acids_bases"}
{"answer": "[H+] je 1 x 10^-4 M, protože 10 na -4 odpovídá pH 4.", "choices": null, "id": "che_0487", "kind": "worked_example", "lang": "cs", "question": "Roztok má pH 4. Vypočítej [H+].", "steps": ["Napiš vzorec: [H+] = 10^(-4).", "Dosaď.", "[H+] = 1 x 10^-4 M."], "subject": "chemistry", "text": "Answer: 1 x 10^-4 M.\nSteps:\n1. Napiš vzorec: [H+] = 10^(-4).\n2. Dosaď.\n3. [H+] = 1 x 10^-4 M.", "topic": "acids_bases"}
{"answer": "The solution is basic because Kb of NH3 exceeds Ka of HCN.", "choices": {"A": "Acidic", "B": "Neutral", "C": "Basic", "D": "Cannot tell"}, "id": "che_0488", "kind": "multiple_choice", "lang": "en", "question": "Is NH4CN solution acidic or basic (Kb NH3 = 1.8e-5, Ka HCN = 6.2e-10)?", "steps": ["Compare Ka and Kb.", "Kb larger means basic.", "Select option C."], "subject": "chemistry", "text": "Answer: Basic.\nSteps:\n1. Compare Ka and Kb.\n2. Kb larger means basic.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "Alkali metals always take oxidation state +1 in compounds.", "choices": null, "id": "che_0489", "kind": "concept", "lang": "en", "question": "What oxidation state do alkali metals take?", "steps": ["Group 1 loses one electron.", "State is +1 always.", "Example: Na in NaCl."], "subject": "chemistry", "text": "Answer: +1 always.\nSteps:\n1. Group 1 loses one electron.\n2. State is +1 always.\n3. Example: Na in NaCl.", "topic": "redox"}
{"answer": "Sodium is +1 in sodium peroxide, as in all its compounds.", "choices": {"A": "+1", "B": "-1", "C": "0", "D": "+2"}, "id": "che_0490", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of Na in Na2O2?", "steps": ["Alkali metals are +1.", "Applies here too.", "Select option A."], "subject": "chemistry", "text": "Answer: +1.\nSteps:\n1. Alkali metals are +1.\n2. Applies here too.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Chlorine is +5, since Cl + 3(-2) = -1 gives Cl = +5.", "choices": null, "id": "che_0491", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of Cl in ClO3-.", "steps": ["Assign O -2.", "Equation: Cl - 6 = -1.", "Cl = +5."], "subject": "chemistry", "text": "Answer: +5.\nSteps:\n1. Assign O -2.\n2. Equation: Cl - 6 = -1.\n3. Cl = +5.", "topic": "redox"}
{"answer": "Oxidace kovů vzduchem je jejich samovolná reakce s kyslíkem.", "choices": null, "id": "che_0492", "kind": "concept", "lang": "cs", "question": "Co je oxidace kovů vzduchem?", "steps": ["Kov odevzdá elektrony.", "Kyslík se redukuje.", "Vznikají oxidy, např. rez."], "subject": "chemistry", "text": "Answer: Tvorba oxidů na kovu.\nSteps:\n1. Kov odevzdá elektrony.\n2. Kyslík se redukuje.\n3. Vznikají oxidy, např. rez.", "topic": "redox"}
{"answer": "Iron drops from +3 to 0, so it is reduced.", "choices": {"A": "Carbon", "B": "Iron", "C": "Oxygen", "D": "CO"}, "id": "che_0493", "kind": "multiple_choice", "lang": "en", "question": "In Fe2O3 + 3CO -> 2Fe + 3CO2, what is reduced?", "steps": ["Fe goes +3 to 0.", "That is reduction.", "Select option B."], "subject": "chemistry", "text": "Answer: Iron.\nSteps:\n1. Fe goes +3 to 0.\n2. That is reduction.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "The balanced ionic equation is Zn + 2Ag+ -> Zn2+ + 2Ag.", "choices": null, "id": "che_0494", "kind": "worked_example", "lang": "en", "question": "Balance: Zn + Ag+ -> Zn2+ + Ag.", "steps": ["Zn loses 2 e-.", "Need 2 Ag+ to gain them.", "Result: Zn + 2Ag+ -> Zn2+ + 2Ag."], "subject": "chemistry", "text": "Answer: Zn + 2Ag+ -> Zn2+ + 2Ag.\nSteps:\n1. Zn loses 2 e-.\n2. Need 2 Ag+ to gain them.\n3. Result: Zn + 2Ag+ -> Zn2+ + 2Ag.", "topic": "redox"}
{"answer": "The oxidation number method tracks electron loss and gain to find coefficients.", "choices": null, "id": "che_0495", "kind": "concept", "lang": "en", "question": "What is the oxidation number method?", "steps": ["Assign all oxidation states.", "Find changes up and down.", "Scale to equalize electrons."], "subject": "chemistry", "text": "Answer: Balance via electron changes.\nSteps:\n1. Assign all oxidation states.\n2. Find changes up and down.\n3. Scale to equalize electrons.", "topic": "redox"}
{"answer": "Six electrons are lost as sulfur rises from -2 to +4.", "choices": null, "id": "che_0496", "kind": "worked_example", "lang": "en", "question": "How many electrons are lost in H2S -> SO2 (S: -2 to +4)?", "steps": ["Change: -2 to +4.", "Difference = 6 up.", "Electrons lost = 6."], "subject": "chemistry", "text": "Answer: 6 electrons.\nSteps:\n1. Change: -2 to +4.\n2. Difference = 6 up.\n3. Electrons lost = 6.", "topic": "redox"}
{"answer": "Sodium metal donates electrons eagerly, making it a strong reducing agent.", "choices": {"A": "Na", "B": "Cl2", "C": "O2", "D": "F2"}, "id": "che_0497", "kind": "multiple_choice", "lang": "en", "question": "Which is the best reducing agent?", "steps": ["Reducers donate electrons.", "Alkali metal Na tops list.", "Select option A."], "subject": "chemistry", "text": "Answer: Na.\nSteps:\n1. Reducers donate electrons.\n2. Alkali metal Na tops list.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Železo má oxidační číslo +2, protože Fe + (-2) = 0.", "choices": null, "id": "che_0498", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo železa v FeO.", "steps": ["Přiřaď O -2.", "Rovnice: Fe - 2 = 0.", "Fe = +2."], "subject": "chemistry", "text": "Answer: +2.\nSteps:\n1. Přiřaď O -2.\n2. Rovnice: Fe - 2 = 0.\n3. Fe = +2.", "topic": "redox"}
{"answer": "Corrosion cells pair anodic metal dissolving with cathodic oxygen reduction.", "choices": null, "id": "che_0499", "kind": "concept", "lang": "en", "question": "What is a corrosion cell?", "steps": ["Anode: metal oxidizes.", "Cathode: O2 reduces.", "Moisture conducts ions."], "subject": "chemistry", "text": "Answer: Anode-cathode rust pair.\nSteps:\n1. Anode: metal oxidizes.\n2. Cathode: O2 reduces.\n3. Moisture conducts ions.", "topic": "redox"}
{"answer": "Paint blocks air and water from reaching the iron surface.", "choices": {"A": "Oxidizes Fe faster", "B": "Adds salt", "C": "Blocks air and water", "D": "Heats the metal"}, "id": "che_0500", "kind": "multiple_choice", "lang": "en", "question": "How does painting prevent rust?", "steps": ["Rust needs O2 and H2O.", "Paint seals them out.", "Select option C."], "subject": "chemistry", "text": "Answer: Blocks air and water.\nSteps:\n1. Rust needs O2 and H2O.\n2. Paint seals them out.\n3. Select option C.\nAnswer: (C)", "topic": "redox"}
{"answer": "The balanced equation is 2Al + 6HCl -> 2AlCl3 + 3H2.", "choices": null, "id": "che_0501", "kind": "worked_example", "lang": "en", "question": "Balance: Al + HCl -> AlCl3 + H2.", "steps": ["Balance Cl and Al with 2 AlCl3, 6 HCl, 2 Al.", "Check H: 6 each side with 3 H2.", "Result: 2Al + 6HCl -> 2AlCl3 + 3H2."], "subject": "chemistry", "text": "Answer: 2Al + 6HCl -> 2AlCl3 + 3H2.\nSteps:\n1. Balance Cl and Al with 2 AlCl3, 6 HCl, 2 Al.\n2. Check H: 6 each side with 3 H2.\n3. Result: 2Al + 6HCl -> 2AlCl3 + 3H2.", "topic": "redox"}
{"answer": "Redoxní pár tvoří oxidovaná a redukovaná forma téže látky.", "choices": null, "id": "che_0502", "kind": "concept", "lang": "cs", "question": "Co je redoxní pár?", "steps": ["Dvě formy jedné látky.", "Liší se o elektrony.", "Příklad: Fe3+/Fe2+."], "subject": "chemistry", "text": "Answer: Oxidovaná a redukovaná forma.\nSteps:\n1. Dvě formy jedné látky.\n2. Liší se o elektrony.\n3. Příklad: Fe3+/Fe2+.", "topic": "redox"}
{"answer": "Carbon is +4, since C + 2(-2) = 0 gives C = +4.", "choices": {"A": "-4", "B": "0", "C": "+2", "D": "+4"}, "id": "che_0503", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of carbon in CO2?", "steps": ["Assign O -2.", "Solve: C - 4 = 0.", "C = +4; select D."], "subject": "chemistry", "text": "Answer: +4.\nSteps:\n1. Assign O -2.\n2. Solve: C - 4 = 0.\n3. C = +4; select D.\nAnswer: (D)", "topic": "redox"}
{"answer": "Hydrogen peroxide disproportionates into water and oxygen: 2H2O2 -> 2H2O + O2.", "choices": null, "id": "che_0504", "kind": "concept", "lang": "en", "question": "How does hydrogen peroxide disproportionate?", "steps": ["O is -1 in H2O2.", "Part goes to -2 in water.", "Part goes to 0 in O2."], "subject": "chemistry", "text": "Answer: 2H2O2 -> 2H2O + O2.\nSteps:\n1. O is -1 in H2O2.\n2. Part goes to -2 in water.\n3. Part goes to 0 in O2.", "topic": "redox"}
{"answer": "Vyčíslená rovnice je 6Li + N2 -> 2Li3N.", "choices": null, "id": "che_0505", "kind": "worked_example", "lang": "cs", "question": "Vyčísli: Li + N2 -> Li3N.", "steps": ["Dusík: 2 Li3N a 1 N2.", "Lithium: 6 Li.", "Výsledek: 6Li + N2 -> 2Li3N."], "subject": "chemistry", "text": "Answer: 6Li + N2 -> 2Li3N.\nSteps:\n1. Dusík: 2 Li3N a 1 N2.\n2. Lithium: 6 Li.\n3. Výsledek: 6Li + N2 -> 2Li3N.", "topic": "redox"}
{"answer": "Oxygen with fluorine is +2, since O + 2(-1) = 0.", "choices": {"A": "-2", "B": "+2", "C": "0", "D": "-1"}, "id": "che_0506", "kind": "multiple_choice", "lang": "en", "question": "What is oxygen's oxidation state in OF2?", "steps": ["F is -1 each.", "Solve: O - 2 = 0.", "O = +2; select B."], "subject": "chemistry", "text": "Answer: +2.\nSteps:\n1. F is -1 each.\n2. Solve: O - 2 = 0.\n3. O = +2; select B.\nAnswer: (B)", "topic": "redox"}
{"answer": "One electron is lost as Fe2+ becomes Fe3+.", "choices": null, "id": "che_0507", "kind": "worked_example", "lang": "en", "question": "How many electrons are lost in Fe2+ -> Fe3+?", "steps": ["Change: +2 to +3.", "Difference = 1 up.", "Electrons lost = 1."], "subject": "chemistry", "text": "Answer: 1 electron.\nSteps:\n1. Change: +2 to +3.\n2. Difference = 1 up.\n3. Electrons lost = 1.", "topic": "redox"}
{"answer": "Open systems exchange matter and energy; closed systems exchange energy only.", "choices": null, "id": "che_0508", "kind": "concept", "lang": "en", "question": "How do open and closed systems differ?", "steps": ["Open: matter crosses.", "Closed: only energy crosses.", "Isolated: neither crosses."], "subject": "chemistry", "text": "Answer: Matter exchange versus energy only.\nSteps:\n1. Open: matter crosses.\n2. Closed: only energy crosses.\n3. Isolated: neither crosses.", "topic": "thermochemistry"}
{"answer": "A closed system exchanges energy but not matter.", "choices": {"A": "Matter only", "B": "Energy only", "C": "Neither", "D": "Both freely"}, "id": "che_0509", "kind": "multiple_choice", "lang": "en", "question": "What does a closed system exchange?", "steps": ["Matter sealed inside.", "Heat and work pass.", "Select option B."], "subject": "chemistry", "text": "Answer: Energy only.\nSteps:\n1. Matter sealed inside.\n2. Heat and work pass.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "The internal energy change is -150 J, from -300 plus +150 J.", "choices": null, "id": "che_0510", "kind": "worked_example", "lang": "en", "question": "A system releases 300 J of heat while 150 J of work is done on it. Find ΔU.", "steps": ["Write: ΔU = -300 + 150.", "Add.", "ΔU = -150 J."], "subject": "chemistry", "text": "Answer: -150 J.\nSteps:\n1. Write: ΔU = -300 + 150.\n2. Add.\n3. ΔU = -150 J.", "topic": "thermochemistry"}
{"answer": "Vnitřní energie je součet kinetické a potenciální energie částic soustavy.", "choices": null, "id": "che_0511", "kind": "concept", "lang": "cs", "question": "Co je vnitřní energie?", "steps": ["Energie částic soustavy.", "Mění se teplem a prací.", "ΔU = q + w."], "subject": "chemistry", "text": "Answer: Energie částic soustavy.\nSteps:\n1. Energie částic soustavy.\n2. Mění se teplem a prací.\n3. ΔU = q + w.", "topic": "thermochemistry"}
{"answer": "Heat leaving the system is negative by convention.", "choices": {"A": "Negative", "B": "Positive", "C": "Zero", "D": "Infinite"}, "id": "che_0512", "kind": "multiple_choice", "lang": "en", "question": "What sign does released heat (q) have?", "steps": ["System loses energy.", "Loss is negative.", "Select option A."], "subject": "chemistry", "text": "Answer: Negative.\nSteps:\n1. System loses energy.\n2. Loss is negative.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "The water releases 62.8 kJ, from 250 x 4.184 x (-60) J.", "choices": null, "id": "che_0513", "kind": "worked_example", "lang": "en", "question": "250 g of water cools from 90 C to 30 C. Find q.", "steps": ["ΔT = 30 - 90 = -60 C.", "q = 250 x 4.184 x (-60).", "q = -62,760 J = -62.8 kJ."], "subject": "chemistry", "text": "Answer: -62.8 kJ.\nSteps:\n1. ΔT = 30 - 90 = -60 C.\n2. q = 250 x 4.184 x (-60).\n3. q = -62,760 J = -62.8 kJ.", "topic": "thermochemistry"}
{"answer": "Thermal equilibrium means no net heat flow because temperatures are equal.", "choices": null, "id": "che_0514", "kind": "concept", "lang": "en", "question": "What is thermal equilibrium?", "steps": ["Bodies in contact.", "Temperatures equalize.", "Net heat flow stops."], "subject": "chemistry", "text": "Answer: Equal temperatures, no flow.\nSteps:\n1. Bodies in contact.\n2. Temperatures equalize.\n3. Net heat flow stops.", "topic": "thermochemistry"}
{"answer": "The final temperature is 50 C, the average of 80 and 20.", "choices": null, "id": "che_0515", "kind": "worked_example", "lang": "en", "question": "100 g of water at 80 C mixes with 100 g at 20 C. Find the final T.", "steps": ["Equal masses and material.", "Average: (80 + 20)/2.", "T = 50 C."], "subject": "chemistry", "text": "Answer: 50 C.\nSteps:\n1. Equal masses and material.\n2. Average: (80 + 20)/2.\n3. T = 50 C.", "topic": "thermochemistry"}
{"answer": "Heat scales with mass, so doubling mass doubles q for the same ΔT.", "choices": {"A": "Halves q", "B": "No change", "C": "Doubles q", "D": "Quadruples q"}, "id": "che_0516", "kind": "multiple_choice", "lang": "en", "question": "Doubling mass with the same ΔT does what to q?", "steps": ["q = m c ΔT.", "m doubles, rest fixed.", "Select option C."], "subject": "chemistry", "text": "Answer: Doubles q.\nSteps:\n1. q = m c ΔT.\n2. m doubles, rest fixed.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "Potřebné teplo je 12 552 J, protože 300 x 4,184 x 10 se rovná 12 552.", "choices": null, "id": "che_0517", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla ohřeje 300 g vody o 10 °C?", "steps": ["Napiš vzorec: q = 300 x 4,184 x 10.", "Vynásob.", "q = 12 552 J."], "subject": "chemistry", "text": "Answer: 12 552 J.\nSteps:\n1. Napiš vzorec: q = 300 x 4,184 x 10.\n2. Vynásob.\n3. q = 12 552 J.", "topic": "thermochemistry"}
{"answer": "Molar heat capacity is the heat to warm one mole by one degree.", "choices": null, "id": "che_0518", "kind": "concept", "lang": "en", "question": "What is molar heat capacity?", "steps": ["Per mole basis.", "Times ΔT gives q.", "Water is 75.4 J/molC."], "subject": "chemistry", "text": "Answer: Heat per mole per degree.\nSteps:\n1. Per mole basis.\n2. Times ΔT gives q.\n3. Water is 75.4 J/molC.", "topic": "thermochemistry"}
{"answer": "Molar heat capacity uses joules per mole per degree.", "choices": {"A": "J/mol C", "B": "J/g only", "C": "kJ/L", "D": "mol/J"}, "id": "che_0519", "kind": "multiple_choice", "lang": "en", "question": "What are molar heat capacity units?", "steps": ["Energy per mole per degree.", "That is J/mol C.", "Select option A."], "subject": "chemistry", "text": "Answer: J/mol C.\nSteps:\n1. Energy per mole per degree.\n2. That is J/mol C.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "The ΔH is -110.5 kJ, from -393.5 minus -283.0 kJ.", "choices": null, "id": "che_0520", "kind": "worked_example", "lang": "en", "question": "Given C+O2->CO2 (-393.5) and CO+1/2O2->CO2 (-283.0 kJ), find C+1/2O2->CO.", "steps": ["Subtract second from first.", "-393.5 - (-283.0).", "ΔH = -110.5 kJ."], "subject": "chemistry", "text": "Answer: -110.5 kJ.\nSteps:\n1. Subtract second from first.\n2. -393.5 - (-283.0).\n3. ΔH = -110.5 kJ.", "topic": "thermochemistry"}
{"answer": "Slučovací teplo je teplo vzniku 1 molu sloučeniny z prvků.", "choices": null, "id": "che_0521", "kind": "concept", "lang": "cs", "question": "Co je slučovací teplo?", "steps": ["Vznik 1 molu z prvků.", "Standardní stavy.", "Příklad: voda -285,8 kJ/mol."], "subject": "chemistry", "text": "Answer: Teplo vzniku z prvků.\nSteps:\n1. Vznik 1 molu z prvků.\n2. Standardní stavy.\n3. Příklad: voda -285,8 kJ/mol.", "topic": "thermochemistry"}
{"answer": "Aqueous H+ is the reference with ΔHf of zero.", "choices": {"A": "100 kJ/mol", "B": "0 kJ/mol", "C": "-50 kJ/mol", "D": "285.8 kJ/mol"}, "id": "che_0522", "kind": "multiple_choice", "lang": "en", "question": "What is ΔHf of H+(aq)?", "steps": ["Reference ion defined zero.", "All ions relative to it.", "Select option B."], "subject": "chemistry", "text": "Answer: 0 kJ/mol.\nSteps:\n1. Reference ion defined zero.\n2. All ions relative to it.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "ΔS universe is +20 J/K, so the process is spontaneous.", "choices": null, "id": "che_0523", "kind": "worked_example", "lang": "en", "question": "ΔS sys = +50 J/K and ΔS surr = -30 J/K. Compute ΔS universe.", "steps": ["Write: ΔS = 50 + (-30).", "Add.", "ΔS = +20 J/K, spontaneous."], "subject": "chemistry", "text": "Answer: +20 J/K.\nSteps:\n1. Write: ΔS = 50 + (-30).\n2. Add.\n3. ΔS = +20 J/K, spontaneous.", "topic": "thermochemistry"}
{"answer": "Druhý zákon říká, že entropie izolované soustavy samovolně roste.", "choices": null, "id": "che_0524", "kind": "concept", "lang": "cs", "question": "Co je druhý termodynamický zákon?", "steps": ["Entropie vesmíru roste.", "Samovolné děje ji zvyšují.", "Teplo neteče samo do teplejšího."], "subject": "chemistry", "text": "Answer: Entropie roste.\nSteps:\n1. Entropie vesmíru roste.\n2. Samovolné děje ji zvyšují.\n3. Teplo neteče samo do teplejšího.", "topic": "thermochemistry"}
{"answer": "Absolute zero is 0 K, the unreachable minimum temperature.", "choices": {"A": "0 C", "B": "-100 C", "C": "273 K", "D": "0 K"}, "id": "che_0525", "kind": "multiple_choice", "lang": "en", "question": "What is absolute zero?", "steps": ["Kelvin scale starts there.", "Equals -273.15 C.", "Select option D."], "subject": "chemistry", "text": "Answer: 0 K.\nSteps:\n1. Kelvin scale starts there.\n2. Equals -273.15 C.\n3. Select option D.\nAnswer: (D)", "topic": "thermochemistry"}
{"answer": "Boiling needs 38.6 kJ, from 1.00 mol times 38.6 kJ/mol.", "choices": null, "id": "che_0526", "kind": "worked_example", "lang": "en", "question": "How much heat boils 46.1 g of ethanol (ΔHvap = 38.6 kJ/mol, M = 46.07 g/mol)?", "steps": ["Moles = 46.1/46.07 = 1.00.", "Multiply: 1.00 x 38.6.", "Heat = 38.6 kJ."], "subject": "chemistry", "text": "Answer: 38.6 kJ.\nSteps:\n1. Moles = 46.1/46.07 = 1.00.\n2. Multiply: 1.00 x 38.6.\n3. Heat = 38.6 kJ.", "topic": "thermochemistry"}
{"answer": "Haloalkane class counts carbons on the halogen-bearing carbon: one is primary, three is tertiary.", "choices": null, "id": "che_0527", "kind": "concept", "lang": "en", "question": "How are alkyl halides classified?", "steps": ["Count carbons on C-X carbon.", "1 primary, 2 secondary, 3 tertiary.", "Reactivity rises with class in SN1."], "subject": "chemistry", "text": "Answer: Primary, secondary, tertiary.\nSteps:\n1. Count carbons on C-X carbon.\n2. 1 primary, 2 secondary, 3 tertiary.\n3. Reactivity rises with class in SN1.", "topic": "organic_naming"}
{"answer": "(CH3)3CBr has three carbons on the C-Br carbon, so it is tertiary.", "choices": {"A": "Primary", "B": "Secondary", "C": "Tertiary", "D": "Aryl"}, "id": "che_0528", "kind": "multiple_choice", "lang": "en", "question": "How is (CH3)3CBr classified?", "steps": ["Count carbons on C-Br: three.", "Three means tertiary.", "Select option C."], "subject": "chemistry", "text": "Answer: Tertiary.\nSteps:\n1. Count carbons on C-Br: three.\n2. Three means tertiary.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "The name is 2-bromopropane: bromine on carbon 2 of three.", "choices": null, "id": "che_0529", "kind": "worked_example", "lang": "en", "question": "Name CH3CHBrCH3.", "steps": ["Count 3 carbons.", "Br on carbon 2.", "Name: 2-bromopropane."], "subject": "chemistry", "text": "Answer: 2-bromopropane.\nSteps:\n1. Count 3 carbons.\n2. Br on carbon 2.\n3. Name: 2-bromopropane.", "topic": "organic_naming"}
{"answer": "Primární alkohol má -OH na uhlíku s jedním dalším uhlíkem.", "choices": null, "id": "che_0530", "kind": "concept", "lang": "cs", "question": "Co je primární alkohol?", "steps": ["-OH na koncovém uhlíku.", "Jeden sousední uhlík.", "Příklad: ethanol."], "subject": "chemistry", "text": "Answer: -OH na primárním uhlíku.\nSteps:\n1. -OH na koncovém uhlíku.\n2. Jeden sousední uhlík.\n3. Příklad: ethanol.", "topic": "organic_naming"}
{"answer": "The -OH sits on a carbon with one neighbor, so it is primary.", "choices": {"A": "Primary", "B": "Secondary", "C": "Tertiary", "D": "Phenol"}, "id": "che_0531", "kind": "multiple_choice", "lang": "en", "question": "How is CH3CH2CH2OH classified?", "steps": ["C-OH has one carbon neighbor.", "One neighbor means primary.", "Select option A."], "subject": "chemistry", "text": "Answer: Primary.\nSteps:\n1. C-OH has one carbon neighbor.\n2. One neighbor means primary.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "Alkenes number the chain to give the double bond the lowest locant.", "choices": null, "id": "che_0532", "kind": "concept", "lang": "en", "question": "How are alkenes numbered?", "steps": ["Find the double bond.", "Number from nearer end.", "Locant goes before -ene."], "subject": "chemistry", "text": "Answer: Lowest locant for C=C.\nSteps:\n1. Find the double bond.\n2. Number from nearer end.\n3. Locant goes before -ene.", "topic": "organic_naming"}
{"answer": "The name is but-2-ene: double bond starting at carbon 2.", "choices": null, "id": "che_0533", "kind": "worked_example", "lang": "en", "question": "Name CH3CH=CHCH3.", "steps": ["Count 4 carbons.", "Double bond at carbon 2.", "Name: but-2-ene."], "subject": "chemistry", "text": "Answer: But-2-ene.\nSteps:\n1. Count 4 carbons.\n2. Double bond at carbon 2.\n3. Name: but-2-ene.", "topic": "organic_naming"}
{"answer": "Cis-trans isomers differ in substituent sides across a rigid double bond.", "choices": null, "id": "che_0534", "kind": "concept", "lang": "en", "question": "What is cis-trans isomerism?", "steps": ["Double bond blocks rotation.", "Same side is cis.", "Opposite side is trans."], "subject": "chemistry", "text": "Answer: Sides across C=C.\nSteps:\n1. Double bond blocks rotation.\n2. Same side is cis.\n3. Opposite side is trans.", "topic": "organic_naming"}
{"answer": "Cis means both methyl groups sit on the same side of the bond.", "choices": {"A": "Opposite sides", "B": "Same side", "C": "No stereochemistry", "D": "Ring form"}, "id": "che_0535", "kind": "multiple_choice", "lang": "en", "question": "What does cis-2-butene look like?", "steps": ["Cis means same side.", "Both CH3 together.", "Select option B."], "subject": "chemistry", "text": "Answer: Same side.\nSteps:\n1. Cis means same side.\n2. Both CH3 together.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "CH2=CH2 je ethen.", "choices": null, "id": "che_0536", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH2=CH2.", "steps": ["Dva uhlíky.", "Dvojná vazba = -en.", "Název: ethen."], "subject": "chemistry", "text": "Answer: Ethen.\nSteps:\n1. Dva uhlíky.\n2. Dvojná vazba = -en.\n3. Název: ethen.", "topic": "organic_naming"}
{"answer": "Alkynes use the -yne suffix with the lowest locant for the triple bond.", "choices": null, "id": "che_0537", "kind": "concept", "lang": "en", "question": "How are alkynes named?", "steps": ["Find the triple bond.", "Lowest locant applies.", "Suffix is -yne."], "subject": "chemistry", "text": "Answer: Lowest locant plus -yne.\nSteps:\n1. Find the triple bond.\n2. Lowest locant applies.\n3. Suffix is -yne.", "topic": "organic_naming"}
{"answer": "HC triple CH with two carbons is ethyne.", "choices": {"A": "Ethene", "B": "Ethane", "C": "Benzene", "D": "Ethyne"}, "id": "che_0538", "kind": "multiple_choice", "lang": "en", "question": "What is the name of HC≡CH?", "steps": ["Two carbons present.", "Triple bond gives -yne.", "Select option D."], "subject": "chemistry", "text": "Answer: Ethyne.\nSteps:\n1. Two carbons present.\n2. Triple bond gives -yne.\n3. Select option D.\nAnswer: (D)", "topic": "organic_naming"}
{"answer": "The name is propyne: three carbons with a triple bond.", "choices": null, "id": "che_0539", "kind": "worked_example", "lang": "en", "question": "Name CH3C≡CH.", "steps": ["Count 3 carbons.", "Triple bond gives -yne.", "Name: propyne."], "subject": "chemistry", "text": "Answer: Propyne.\nSteps:\n1. Count 3 carbons.\n2. Triple bond gives -yne.\n3. Name: propyne.", "topic": "organic_naming"}
{"answer": "Phenyl is the C6H5- group used as a substituent name.", "choices": null, "id": "che_0540", "kind": "concept", "lang": "en", "question": "What does phenyl mean in naming?", "steps": ["Benzene minus one H.", "Attaches as substituent.", "Example: phenylamine."], "subject": "chemistry", "text": "Answer: C6H5- substituent.\nSteps:\n1. Benzene minus one H.\n2. Attaches as substituent.\n3. Example: phenylamine.", "topic": "organic_naming"}
{"answer": "Fenyl je skupina C6H5- odvozená od benzenu.", "choices": null, "id": "che_0541", "kind": "concept", "lang": "cs", "question": "Co je fenyl?", "steps": ["Benzen bez jednoho H.", "Substituent v názvech.", "Příklad: fenylamin."], "subject": "chemistry", "text": "Answer: Skupina C6H5-.\nSteps:\n1. Benzen bez jednoho H.\n2. Substituent v názvech.\n3. Příklad: fenylamin.", "topic": "organic_naming"}
{"answer": "The C6H5- fragment is called phenyl.", "choices": {"A": "Phenyl", "B": "Benzyl", "C": "Methyl", "D": "Ethyl"}, "id": "che_0542", "kind": "multiple_choice", "lang": "en", "question": "What is the C6H5- group called?", "steps": ["Benzene ring fragment.", "Named phenyl.", "Select option A."], "subject": "chemistry", "text": "Answer: Phenyl.\nSteps:\n1. Benzene ring fragment.\n2. Named phenyl.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "The name is butanoic acid: four carbons ending in -COOH.", "choices": null, "id": "che_0543", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2CH2COOH.", "steps": ["Count 4 carbons.", "-COOH gives -oic acid.", "Name: butanoic acid."], "subject": "chemistry", "text": "Answer: Butanoic acid.\nSteps:\n1. Count 4 carbons.\n2. -COOH gives -oic acid.\n3. Name: butanoic acid.", "topic": "organic_naming"}
{"answer": "C6H6 je benzen.", "choices": null, "id": "che_0544", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu C6H6.", "steps": ["Šestičlenný kruh.", "Aromatické elektrony.", "Název: benzen."], "subject": "chemistry", "text": "Answer: Benzen.\nSteps:\n1. Šestičlenný kruh.\n2. Aromatické elektrony.\n3. Název: benzen.", "topic": "organic_naming"}
{"answer": "Ethers name the smaller group as alkoxy on the larger chain.", "choices": null, "id": "che_0545", "kind": "concept", "lang": "en", "question": "How are ethers named systematically?", "steps": ["Smaller part is alkoxy.", "Larger part is parent.", "Example: methoxyethane."], "subject": "chemistry", "text": "Answer: Alkoxy plus parent.\nSteps:\n1. Smaller part is alkoxy.\n2. Larger part is parent.\n3. Example: methoxyethane.", "topic": "organic_naming"}
{"answer": "Nucleophilic substitution swaps a leaving group for a nucleophile.", "choices": null, "id": "che_0546", "kind": "concept", "lang": "en", "question": "What is nucleophilic substitution?", "steps": ["Nucleophile attacks carbon.", "Leaving group departs.", "SN1 or SN2 pathway."], "subject": "chemistry", "text": "Answer: Nu replaces leaving group.\nSteps:\n1. Nucleophile attacks carbon.\n2. Leaving group departs.\n3. SN1 or SN2 pathway.", "topic": "organic_mechanisms"}
{"answer": "SN2 rate depends on both substrate and nucleophile concentrations.", "choices": {"A": "k[RX] only", "B": "k[RX][Nu]", "C": "k[Nu] only", "D": "k always"}, "id": "che_0547", "kind": "multiple_choice", "lang": "en", "question": "What is the SN2 rate law?", "steps": ["One step with both.", "Rate = k[RX][Nu].", "Select option B."], "subject": "chemistry", "text": "Answer: k[RX][Nu].\nSteps:\n1. One step with both.\n2. Rate = k[RX][Nu].\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "The SN2 rate triples to 3x because rate scales with [Nu].", "choices": null, "id": "che_0548", "kind": "worked_example", "lang": "en", "question": "SN2 rate = k[RX][Nu]. What happens if [Nu] triples?", "steps": ["Write: rate = k[RX] x 3[Nu].", "Factor: 3 x k[RX][Nu].", "Rate becomes 3x."], "subject": "chemistry", "text": "Answer: Rate triples.\nSteps:\n1. Write: rate = k[RX] x 3[Nu].\n2. Factor: 3 x k[RX][Nu].\n3. Rate becomes 3x.", "topic": "organic_mechanisms"}
{"answer": "Nukleofilní substituce nahradí odstupující skupinu nukleofilem.", "choices": null, "id": "che_0549", "kind": "concept", "lang": "cs", "question": "Co je nukleofilní substituce?", "steps": ["Nukleofil napadne uhlík.", "Skupina odstoupí.", "Mechanismus SN1 nebo SN2."], "subject": "chemistry", "text": "Answer: Náhrada skupiny nukleofilem.\nSteps:\n1. Nukleofil napadne uhlík.\n2. Skupina odstoupí.\n3. Mechanismus SN1 nebo SN2.", "topic": "organic_mechanisms"}
{"answer": "Polar aprotic solvents free nucleophiles and speed SN2.", "choices": null, "id": "che_0550", "kind": "concept", "lang": "en", "question": "Which solvents favor SN2?", "steps": ["Nucleophile must stay free.", "Aprotic avoids H-bond cage.", "Examples: acetone, DMSO."], "subject": "chemistry", "text": "Answer: Polar aprotic solvents.\nSteps:\n1. Nucleophile must stay free.\n2. Aprotic avoids H-bond cage.\n3. Examples: acetone, DMSO.", "topic": "organic_mechanisms"}
{"answer": "Polar aprotic solvents leave nucleophiles free to attack.", "choices": {"A": "Polar protic", "B": "Nonpolar only", "C": "Polar aprotic", "D": "Water only"}, "id": "che_0551", "kind": "multiple_choice", "lang": "en", "question": "Which solvent class speeds SN2 most?", "steps": ["Free nucleophile needed.", "Aprotic avoids caging.", "Select option C."], "subject": "chemistry", "text": "Answer: Polar aprotic.\nSteps:\n1. Free nucleophile needed.\n2. Aprotic avoids caging.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "HBr adds across ethene to give bromoethane.", "choices": null, "id": "che_0552", "kind": "worked_example", "lang": "en", "question": "What is the product of HBr addition to ethene?", "steps": ["H adds to one carbon.", "Br adds to the other.", "Product: bromoethane."], "subject": "chemistry", "text": "Answer: Bromoethane.\nSteps:\n1. H adds to one carbon.\n2. Br adds to the other.\n3. Product: bromoethane.", "topic": "organic_mechanisms"}
{"answer": "Carbocations rearrange by hydride or alkyl shifts toward greater stability.", "choices": null, "id": "che_0553", "kind": "concept", "lang": "en", "question": "How do carbocations rearrange?", "steps": ["Neighbor H or alkyl shifts.", "Charge moves to stabler carbon.", "Tertiary preferred."], "subject": "chemistry", "text": "Answer: Shifts toward stability.\nSteps:\n1. Neighbor H or alkyl shifts.\n2. Charge moves to stabler carbon.\n3. Tertiary preferred.", "topic": "organic_mechanisms"}
{"answer": "Hydridový přesmyk přesune H- na sousední karbokation.", "choices": null, "id": "che_0554", "kind": "concept", "lang": "cs", "question": "Co je hydridový přesmyk?", "steps": ["H- migruje ke kationu.", "Náboj se přesune.", "Stabilnější kation vznikne."], "subject": "chemistry", "text": "Answer: Migrace H- ke kationu.\nSteps:\n1. H- migruje ke kationu.\n2. Náboj se přesune.\n3. Stabilnější kation vznikne.", "topic": "organic_mechanisms"}
{"answer": "A methyl shift relocates a CH3 group to the cationic center.", "choices": {"A": "CH3 group", "B": "H-", "C": "Leaving group", "D": "Proton"}, "id": "che_0555", "kind": "multiple_choice", "lang": "en", "question": "What moves in a methyl shift?", "steps": ["Methyl migrates.", "Carries bonding pair.", "Select option A."], "subject": "chemistry", "text": "Answer: CH3 group.\nSteps:\n1. Methyl migrates.\n2. Carries bonding pair.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "The product is 2-chloropropane, with Cl on the middle carbon.", "choices": null, "id": "che_0556", "kind": "worked_example", "lang": "en", "question": "What is the HCl addition product of propene?", "steps": ["H adds to C1.", "Secondary cation forms.", "Cl captures it: 2-chloropropane."], "subject": "chemistry", "text": "Answer: 2-chloropropane.\nSteps:\n1. H adds to C1.\n2. Secondary cation forms.\n3. Cl captures it: 2-chloropropane.", "topic": "organic_mechanisms"}
{"answer": "Backside attack in SN2 flips the stereocenter like an umbrella.", "choices": null, "id": "che_0557", "kind": "concept", "lang": "en", "question": "Why does SN2 invert stereochemistry?", "steps": ["Attack comes from behind.", "Bonds flip over.", "Configuration inverts."], "subject": "chemistry", "text": "Answer: Backside attack flips center.\nSteps:\n1. Attack comes from behind.\n2. Bonds flip over.\n3. Configuration inverts.", "topic": "organic_mechanisms"}
{"answer": "The product is 2-bromobutane, via the secondary carbocation.", "choices": null, "id": "che_0558", "kind": "worked_example", "lang": "en", "question": "What is the HBr addition product of 1-butene?", "steps": ["H adds to C1.", "Cation forms on C2.", "Br captures it: 2-bromobutane."], "subject": "chemistry", "text": "Answer: 2-bromobutane.\nSteps:\n1. H adds to C1.\n2. Cation forms on C2.\n3. Br captures it: 2-bromobutane.", "topic": "organic_mechanisms"}
{"answer": "SN2 always inverts the configuration at the attacked carbon.", "choices": {"A": "Retention", "B": "Racemization", "C": "No change", "D": "Inversion"}, "id": "che_0559", "kind": "multiple_choice", "lang": "en", "question": "What stereochemistry results from SN2?", "steps": ["Backside attack occurs.", "Center flips.", "Select option D."], "subject": "chemistry", "text": "Answer: Inversion.\nSteps:\n1. Backside attack occurs.\n2. Center flips.\n3. Select option D.\nAnswer: (D)", "topic": "organic_mechanisms"}
{"answer": "Eliminací 2-brompropanu vzniká propen.", "choices": null, "id": "che_0560", "kind": "worked_example", "lang": "cs", "question": "Jaký produkt vznikne eliminací 2-brompropanu se silnou bází?", "steps": ["Odstoupí Br a sousední H.", "Vznikne dvojná vazba.", "Produkt: propen."], "subject": "chemistry", "text": "Answer: Propen.\nSteps:\n1. Odstoupí Br a sousední H.\n2. Vznikne dvojná vazba.\n3. Produkt: propen.", "topic": "organic_mechanisms"}
{"answer": "Halogenation prefers tertiary H over secondary over primary.", "choices": null, "id": "che_0561", "kind": "concept", "lang": "en", "question": "What is the selectivity of radical halogenation?", "steps": ["Weaker C-H breaks first.", "Order: 3° > 2° > 1°.", "Bromine most selective."], "subject": "chemistry", "text": "Answer: Tertiary > secondary > primary.\nSteps:\n1. Weaker C-H breaks first.\n2. Order: 3° > 2° > 1°.\n3. Bromine most selective.", "topic": "organic_mechanisms"}
{"answer": "Propane gives 1-chloropropane and 2-chloropropane as a mixture.", "choices": null, "id": "che_0562", "kind": "worked_example", "lang": "en", "question": "What products come from propane monochlorination?", "steps": ["Primary H gives 1-chloro.", "Secondary H gives 2-chloro.", "Both form as a mixture."], "subject": "chemistry", "text": "Answer: 1-chloro and 2-chloropropane.\nSteps:\n1. Primary H gives 1-chloro.\n2. Secondary H gives 2-chloro.\n3. Both form as a mixture.", "topic": "organic_mechanisms"}
{"answer": "Tertiary hydrogens abstract fastest in radical halogenation.", "choices": {"A": "Primary", "B": "Secondary", "C": "Tertiary", "D": "Aromatic"}, "id": "che_0563", "kind": "multiple_choice", "lang": "en", "question": "Which hydrogen reacts fastest in halogenation?", "steps": ["Weakest C-H wins.", "Tertiary is weakest.", "Select option C."], "subject": "chemistry", "text": "Answer: Tertiary.\nSteps:\n1. Weakest C-H wins.\n2. Tertiary is weakest.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "Elektrofil je částice chudá na elektrony, která je přijímá.", "choices": null, "id": "che_0564", "kind": "concept", "lang": "cs", "question": "Co je elektrofil?", "steps": ["Chudý na elektrony.", "Napadá nukleofil.", "Příklad: H+, NO2+."], "subject": "chemistry", "text": "Answer: Akceptor elektronového páru.\nSteps:\n1. Chudý na elektrony.\n2. Napadá nukleofil.\n3. Příklad: H+, NO2+.", "topic": "organic_mechanisms"}
{"answer": "At equilibrium ΔG is zero and forward and reverse rates match.", "choices": null, "id": "che_0565", "kind": "concept", "lang": "en", "question": "How does Gibbs energy relate to equilibrium?", "steps": ["ΔG drives change.", "Zero means no drive.", "Rates are equal there."], "subject": "chemistry", "text": "Answer: ΔG = 0 at equilibrium.\nSteps:\n1. ΔG drives change.\n2. Zero means no drive.\n3. Rates are equal there.", "topic": "equilibrium"}
{"answer": "Dynamic equilibrium has equal forward and reverse rates.", "choices": {"A": "Equal", "B": "Zero both", "C": "Forward faster", "D": "Reverse faster"}, "id": "che_0566", "kind": "multiple_choice", "lang": "en", "question": "How do forward and reverse rates compare at equilibrium?", "steps": ["Both still run.", "Rates match.", "Select option A."], "subject": "chemistry", "text": "Answer: Equal.\nSteps:\n1. Both still run.\n2. Rates match.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "The overall K is 5, from 10 times 0.5.", "choices": null, "id": "che_0567", "kind": "worked_example", "lang": "en", "question": "Step 1 has K1 = 10 and step 2 has K2 = 0.5. Find overall K.", "steps": ["Multiply step constants.", "K = 10 x 0.5.", "K = 5."], "subject": "chemistry", "text": "Answer: 5.\nSteps:\n1. Multiply step constants.\n2. K = 10 x 0.5.\n3. K = 5.", "topic": "equilibrium"}
{"answer": "Rovnovážná směs obsahuje reaktanty i produkty ve stálých koncentracích.", "choices": null, "id": "che_0568", "kind": "concept", "lang": "cs", "question": "Co je rovnovážná směs?", "steps": ["Oba směry běží.", "Koncentrace stálé.", "Poměr určuje K."], "subject": "chemistry", "text": "Answer: Směs reaktantů a produktů.\nSteps:\n1. Oba směry běží.\n2. Koncentrace stálé.\n3. Poměr určuje K.", "topic": "equilibrium"}
{"answer": "Halving all coefficients takes the square root of K.", "choices": {"A": "K squared", "B": "2K", "C": "Square root of K", "D": "K halved"}, "id": "che_0569", "kind": "multiple_choice", "lang": "en", "question": "What happens to K when the equation is halved?", "steps": ["Exponents halve.", "That roots the value.", "Select option C."], "subject": "chemistry", "text": "Answer: Square root of K.\nSteps:\n1. Exponents halve.\n2. That roots the value.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "The system shifts left because Q = 20 exceeds K = 5.", "choices": null, "id": "che_0570", "kind": "worked_example", "lang": "en", "question": "Q = 20 and K = 5. Which way does the system shift?", "steps": ["Compare: 20 > 5.", "Too many products.", "Shifts left."], "subject": "chemistry", "text": "Answer: Shifts left.\nSteps:\n1. Compare: 20 > 5.\n2. Too many products.\n3. Shifts left.", "topic": "equilibrium"}
{"answer": "A catalyst at equilibrium only helps reach it faster, changing nothing else.", "choices": null, "id": "che_0571", "kind": "concept", "lang": "en", "question": "What does adding a catalyst at equilibrium do?", "steps": ["Both rates rise.", "K unchanged.", "No shift occurs."], "subject": "chemistry", "text": "Answer: Nothing but faster balance.\nSteps:\n1. Both rates rise.\n2. K unchanged.\n3. No shift occurs.", "topic": "equilibrium"}
{"answer": "The catalyst leaves the equilibrium position untouched.", "choices": {"A": "Shifts right", "B": "No shift", "C": "Shifts left", "D": "Destroys K"}, "id": "che_0572", "kind": "multiple_choice", "lang": "en", "question": "A catalyst is added at equilibrium. What shift follows?", "steps": ["Rates rise equally.", "Position unchanged.", "Select option B."], "subject": "chemistry", "text": "Answer: No shift.\nSteps:\n1. Rates rise equally.\n2. Position unchanged.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "Doubling volume lowers pressure, shifting toward more gas moles.", "choices": null, "id": "che_0573", "kind": "worked_example", "lang": "en", "question": "Volume doubles for N2O4 <-> 2NO2. Which way is the shift?", "steps": ["Pressure drops.", "System favors more moles.", "Shifts right to NO2."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Pressure drops.\n2. System favors more moles.\n3. Shifts right to NO2.", "topic": "equilibrium"}
{"answer": "Při stejném počtu molů plynu tlak rovnováhu neposune.", "choices": null, "id": "che_0574", "kind": "worked_example", "lang": "cs", "question": "Jak ovlivní tlak rovnováhu se stejnými moly plynu na obou stranách?", "steps": ["Moly se rovnají.", "Žádná strana nezvýhodněna.", "Žádný posun."], "subject": "chemistry", "text": "Answer: Žádný posun.\nSteps:\n1. Moly se rovnají.\n2. Žádná strana nezvýhodněna.\n3. Žádný posun.", "topic": "equilibrium"}
{"answer": "Pressure cannot favor either side when gas moles are equal.", "choices": {"A": "Shifts right", "B": "Shifts left", "C": "K changes", "D": "No shift"}, "id": "che_0575", "kind": "multiple_choice", "lang": "en", "question": "Equal gas moles on both sides: what does pressure do?", "steps": ["No mole advantage.", "Q unchanged.", "Select option D."], "subject": "chemistry", "text": "Answer: No shift.\nSteps:\n1. No mole advantage.\n2. Q unchanged.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "Heating an endothermic reaction raises K as products gain favor.", "choices": null, "id": "che_0576", "kind": "concept", "lang": "en", "question": "How does temperature change K for endothermic reactions?", "steps": ["Heat acts as reactant.", "Warming shifts right.", "K grows."], "subject": "chemistry", "text": "Answer: K rises with temperature.\nSteps:\n1. Heat acts as reactant.\n2. Warming shifts right.\n3. K grows.", "topic": "equilibrium"}
{"answer": "Rising K with temperature marks the reaction as endothermic.", "choices": null, "id": "che_0577", "kind": "worked_example", "lang": "en", "question": "K doubles when heated. Is the reaction endo- or exothermic?", "steps": ["K rises with T.", "Heat favors products.", "Endothermic."], "subject": "chemistry", "text": "Answer: Endothermic.\nSteps:\n1. K rises with T.\n2. Heat favors products.\n3. Endothermic.", "topic": "equilibrium"}
{"answer": "A growing K on heating means heat is consumed: endothermic.", "choices": {"A": "Endothermic", "B": "Exothermic", "C": "Athermal", "D": "Impossible"}, "id": "che_0578", "kind": "multiple_choice", "lang": "en", "question": "Heating increases K. What type of reaction is it?", "steps": ["K up means products favored.", "Heat drives it.", "Select option A."], "subject": "chemistry", "text": "Answer: Endothermic.\nSteps:\n1. K up means products favored.\n2. Heat drives it.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "Compare the ion product Q to Ksp: above it, solid precipitates.", "choices": null, "id": "che_0579", "kind": "concept", "lang": "en", "question": "How do Q and Ksp predict precipitation?", "steps": ["Compute ion product Q.", "Compare to Ksp.", "Q > Ksp means precipitate."], "subject": "chemistry", "text": "Answer: Q above Ksp precipitates.\nSteps:\n1. Compute ion product Q.\n2. Compare to Ksp.\n3. Q > Ksp means precipitate.", "topic": "equilibrium"}
{"answer": "Srážení je vznik pevné látky z roztoku při překročení rozpustnosti.", "choices": null, "id": "che_0580", "kind": "concept", "lang": "cs", "question": "Co je srážení?", "steps": ["Ionty překročí Ksp.", "Vznikne sraženina.", "Příklad: AgCl z Ag+ a Cl-."], "subject": "chemistry", "text": "Answer: Vznik pevné látky z roztoku.\nSteps:\n1. Ionty překročí Ksp.\n2. Vznikne sraženina.\n3. Příklad: AgCl z Ag+ a Cl-.", "topic": "equilibrium"}
{"answer": "Excess ions beyond saturation fall out as solid.", "choices": {"A": "More dissolves", "B": "Precipitate forms", "C": "Nothing happens", "D": "Gas evolves"}, "id": "che_0581", "kind": "multiple_choice", "lang": "en", "question": "What happens when Q exceeds Ksp?", "steps": ["Solution is supersaturated.", "Excess must leave.", "Select option B."], "subject": "chemistry", "text": "Answer: Precipitate forms.\nSteps:\n1. Solution is supersaturated.\n2. Excess must leave.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "No precipitate forms because Q = 1.0 x 10^-10 is below Ksp = 1.8 x 10^-10.", "choices": null, "id": "che_0582", "kind": "worked_example", "lang": "en", "question": "[Ag+] = 1.0e-5 M and [Cl-] = 1.0e-5 M. Does AgCl precipitate (Ksp = 1.8e-10)?", "steps": ["Q = 1.0e-5 x 1.0e-5 = 1.0e-10.", "Compare: 1.0e-10 < 1.8e-10.", "No precipitate."], "subject": "chemistry", "text": "Answer: No precipitate.\nSteps:\n1. Q = 1.0e-5 x 1.0e-5 = 1.0e-10.\n2. Compare: 1.0e-10 < 1.8e-10.\n3. No precipitate.", "topic": "equilibrium"}
{"answer": "The Daniell cell pairs zinc and copper half-cells for a steady 1.10 V.", "choices": null, "id": "che_0583", "kind": "concept", "lang": "en", "question": "What is a Daniell cell?", "steps": ["Zn anode dissolves.", "Cu cathode plates.", "Salt bridge joins halves."], "subject": "chemistry", "text": "Answer: Zn/Cu galvanic cell.\nSteps:\n1. Zn anode dissolves.\n2. Cu cathode plates.\n3. Salt bridge joins halves.", "topic": "electrochemistry"}
{"answer": "The Daniell cell uses zinc and copper electrodes.", "choices": {"A": "Zn and Cu", "B": "Pb and PbO2", "C": "Ag and Au", "D": "Fe and Ni"}, "id": "che_0584", "kind": "multiple_choice", "lang": "en", "question": "Which electrodes does a Daniell cell use?", "steps": ["Classic Zn/Cu pair.", "Eliminate others.", "Select option A."], "subject": "chemistry", "text": "Answer: Zn and Cu.\nSteps:\n1. Classic Zn/Cu pair.\n2. Eliminate others.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "The cell potential is 0.59 V, from 0.34 - (-0.25).", "choices": null, "id": "che_0585", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Ni/Cu with E(Ni) = -0.25 V and E(Cu) = 0.34 V.", "steps": ["Cathode is Cu at 0.34 V.", "Anode is Ni at -0.25 V.", "E = 0.34 - (-0.25) = 0.59 V."], "subject": "chemistry", "text": "Answer: 0.59 V.\nSteps:\n1. Cathode is Cu at 0.34 V.\n2. Anode is Ni at -0.25 V.\n3. E = 0.34 - (-0.25) = 0.59 V.", "topic": "electrochemistry"}
{"answer": "Daniellův článek spojuje zinkovou a měděnou polovinu o napětí 1,10 V.", "choices": null, "id": "che_0586", "kind": "concept", "lang": "cs", "question": "Co je Daniellův článek?", "steps": ["Zinková anoda.", "Měděná katoda.", "Solný můstek spojuje."], "subject": "chemistry", "text": "Answer: Zn/Cu článek 1,10 V.\nSteps:\n1. Zinková anoda.\n2. Měděná katoda.\n3. Solný můstek spojuje.", "topic": "electrochemistry"}
{"answer": "Conventional current flows opposite to electrons: cathode to anode externally.", "choices": {"A": "Anode to cathode", "B": "Cathode to anode", "C": "No flow", "D": "Alternating"}, "id": "che_0587", "kind": "multiple_choice", "lang": "en", "question": "Which way does conventional current flow in the external wire?", "steps": ["Electrons go anode to cathode.", "Current is defined opposite.", "Select option B."], "subject": "chemistry", "text": "Answer: Cathode to anode.\nSteps:\n1. Electrons go anode to cathode.\n2. Current is defined opposite.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "Overpotential is the extra voltage beyond E needed to drive electrolysis at a rate.", "choices": null, "id": "che_0588", "kind": "concept", "lang": "en", "question": "What is overpotential?", "steps": ["Kinetics resist reaction.", "Extra voltage overcomes it.", "Varies by electrode."], "subject": "chemistry", "text": "Answer: Extra voltage for kinetics.\nSteps:\n1. Kinetics resist reaction.\n2. Extra voltage overcomes it.\n3. Varies by electrode.", "topic": "electrochemistry"}
{"answer": "The potential is 1.16 V, from 1.10 - 0.0296 x log(0.01).", "choices": null, "id": "che_0589", "kind": "worked_example", "lang": "en", "question": "E° = 1.10 V, n = 2, Q = 0.01 at 25 C. Compute E.", "steps": ["Write: E = 1.10 - 0.0296 x log(0.01).", "log(0.01) = -2.", "E = 1.10 + 0.0592 = 1.16 V."], "subject": "chemistry", "text": "Answer: 1.16 V.\nSteps:\n1. Write: E = 1.10 - 0.0296 x log(0.01).\n2. log(0.01) = -2.\n3. E = 1.10 + 0.0592 = 1.16 V.", "topic": "electrochemistry"}
{"answer": "K is about 3.5 x 10^15, from log K = 2 x 0.46 / 0.0592 = 15.54.", "choices": null, "id": "che_0590", "kind": "worked_example", "lang": "en", "question": "A cell has n = 2 and E° = 0.46 V. Estimate K at 25 C.", "steps": ["Write: log K = nE°/0.0592.", "Substitute: 2 x 0.46/0.0592 = 15.54.", "K = 10^15.54 = 3.5 x 10^15."], "subject": "chemistry", "text": "Answer: 3.5 x 10^15.\nSteps:\n1. Write: log K = nE°/0.0592.\n2. Substitute: 2 x 0.46/0.0592 = 15.54.\n3. K = 10^15.54 = 3.5 x 10^15.", "topic": "electrochemistry"}
{"answer": "A large positive E° means a huge equilibrium constant favoring products.", "choices": {"A": "Tiny K", "B": "K is zero", "C": "Very large K", "D": "Negative K"}, "id": "che_0591", "kind": "multiple_choice", "lang": "en", "question": "What K matches a large positive E°?", "steps": ["log K scales with E°.", "Large E° gives huge K.", "Select option C."], "subject": "chemistry", "text": "Answer: Very large K.\nSteps:\n1. log K scales with E°.\n2. Large E° gives huge K.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "Fuel cells convert fuel and oxygen directly into electricity and water.", "choices": null, "id": "che_0592", "kind": "concept", "lang": "en", "question": "How does a fuel cell work?", "steps": ["Fuel oxidizes at anode.", "Oxygen reduces at cathode.", "Steady feed sustains power."], "subject": "chemistry", "text": "Answer: Fuel plus O2 give power.\nSteps:\n1. Fuel oxidizes at anode.\n2. Oxygen reduces at cathode.\n3. Steady feed sustains power.", "topic": "electrochemistry"}
{"answer": "Náboj je 7200 C, protože 2 A krát 3600 s se rovná 7200 C.", "choices": null, "id": "che_0593", "kind": "worked_example", "lang": "cs", "question": "Jaký náboj proteče při 2 A za 1 hodinu?", "steps": ["Převeď čas: 3600 s.", "Q = 2 x 3600.", "Q = 7200 C."], "subject": "chemistry", "text": "Answer: 7200 C.\nSteps:\n1. Převeď čas: 3600 s.\n2. Q = 2 x 3600.\n3. Q = 7200 C.", "topic": "electrochemistry"}
{"answer": "The plated zinc mass is 1.22 g, from 3600 C giving 0.01866 mol Zn.", "choices": null, "id": "che_0594", "kind": "worked_example", "lang": "en", "question": "What mass of Zn plates at 2.00 A for 30.0 min (M = 65.38 g/mol)?", "steps": ["Q = 2.00 x 1800 = 3600 C.", "Mol e- = 0.03731; Zn = 0.01866 mol.", "Mass = 0.01866 x 65.38 = 1.22 g."], "subject": "chemistry", "text": "Answer: 1.22 g.\nSteps:\n1. Q = 2.00 x 1800 = 3600 C.\n2. Mol e- = 0.03731; Zn = 0.01866 mol.\n3. Mass = 0.01866 x 65.38 = 1.22 g.", "topic": "electrochemistry"}
{"answer": "The anode supplies the plating metal by dissolving into the bath.", "choices": {"A": "Plating metal", "B": "Object", "C": "Inert rod", "D": "Plastic"}, "id": "che_0595", "kind": "multiple_choice", "lang": "en", "question": "In electroplating, what is the anode made of?", "steps": ["Anode dissolves to feed ions.", "Made of plating metal.", "Select option A."], "subject": "chemistry", "text": "Answer: Plating metal.\nSteps:\n1. Anode dissolves to feed ions.\n2. Made of plating metal.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "Pipelines gain cathodic protection from buried sacrificial anodes.", "choices": null, "id": "che_0596", "kind": "concept", "lang": "en", "question": "How are pipelines protected from corrosion?", "steps": ["Bury Mg or Zn anodes.", "They corrode instead.", "Pipe stays cathodic."], "subject": "chemistry", "text": "Answer: Sacrificial anodes.\nSteps:\n1. Bury Mg or Zn anodes.\n2. They corrode instead.\n3. Pipe stays cathodic.", "topic": "electrochemistry"}
{"answer": "The oxygen volume is 22.4 L, from 1.00 mol times 22.414 L/mol.", "choices": null, "id": "che_0597", "kind": "worked_example", "lang": "en", "question": "What volume of O2 at STP comes from 4.00 mol of electrons?", "steps": ["4 e- give 1 O2: 1.00 mol.", "Multiply: 1.00 x 22.414.", "V = 22.4 L."], "subject": "chemistry", "text": "Answer: 22.4 L.\nSteps:\n1. 4 e- give 1 O2: 1.00 mol.\n2. Multiply: 1.00 x 22.414.\n3. V = 22.4 L.", "topic": "electrochemistry"}
{"answer": "Palivový článek mění palivo a kyslík přímo na elektřinu a vodu.", "choices": null, "id": "che_0598", "kind": "concept", "lang": "cs", "question": "Co je palivový článek?", "steps": ["Vodík na anodě.", "Kyslík na katodě.", "Trvalý přívod = výkon."], "subject": "chemistry", "text": "Answer: Přímá přeměna paliva na proud.\nSteps:\n1. Vodík na anodě.\n2. Kyslík na katodě.\n3. Trvalý přívod = výkon.", "topic": "electrochemistry"}
{"answer": "Hydrogen fuel cells combine H2 and O2 into water and power.", "choices": {"A": "Coal", "B": "Hydrogen", "C": "Uranium", "D": "Gasoline"}, "id": "che_0599", "kind": "multiple_choice", "lang": "en", "question": "What fuel do common fuel cells use?", "steps": ["H2 oxidizes cleanly.", "Only water forms.", "Select option B."], "subject": "chemistry", "text": "Answer: Hydrogen.\nSteps:\n1. H2 oxidizes cleanly.\n2. Only water forms.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "The charge is 9.57 x 10^4 C, from 0.992 mol of electrons.", "choices": null, "id": "che_0600", "kind": "worked_example", "lang": "en", "question": "What charge makes 1.00 g of H2 by electrolysis (M = 2.016 g/mol)?", "steps": ["Mol H2 = 1.00/2.016 = 0.496.", "Mol e- = 0.992.", "Q = 0.992 x 96485 = 9.57 x 10^4 C."], "subject": "chemistry", "text": "Answer: 9.57 x 10^4 C.\nSteps:\n1. Mol H2 = 1.00/2.016 = 0.496.\n2. Mol e- = 0.992.\n3. Q = 0.992 x 96485 = 9.57 x 10^4 C.", "topic": "electrochemistry"}
{"answer": "Chemists count particles by weighing because moles link atomic mass to grams.", "choices": null, "id": "che_0601", "kind": "concept", "lang": "en", "question": "Why do chemists use moles?", "steps": ["Atoms are too small to count.", "Moles group 6e23 particles.", "Mass in grams equals atomic mass."], "subject": "chemistry", "text": "Answer: Counting particles by weighing.\nSteps:\n1. Atoms are too small to count.\n2. Moles group 6e23 particles.\n3. Mass in grams equals atomic mass.", "topic": "stoichiometry"}
{"answer": "The mass is 15.89 g, from 0.250 mol times 63.55 g/mol.", "choices": {"A": "7.94 g", "B": "31.78 g", "C": "15.89 g", "D": "63.55 g"}, "id": "che_0602", "kind": "multiple_choice", "lang": "en", "question": "What mass is 0.250 mol of copper (M = 63.55 g/mol)?", "steps": ["Write: m = 0.250 x 63.55.", "Multiply: 15.89.", "Select option C."], "subject": "chemistry", "text": "Answer: 15.89 g.\nSteps:\n1. Write: m = 0.250 x 63.55.\n2. Multiply: 15.89.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "There are 0.185 mol, from 5.00 g divided by 26.98 g/mol.", "choices": null, "id": "che_0603", "kind": "worked_example", "lang": "en", "question": "How many moles are in 5.00 g of aluminum (M = 26.98 g/mol)?", "steps": ["Write: n = 5.00/26.98.", "Divide.", "n = 0.185 mol."], "subject": "chemistry", "text": "Answer: 0.185 mol.\nSteps:\n1. Write: n = 5.00/26.98.\n2. Divide.\n3. n = 0.185 mol.", "topic": "stoichiometry"}
{"answer": "Molární objem plynu je objem 1 molu plynu, za STP 22,414 l/mol.", "choices": null, "id": "che_0604", "kind": "concept", "lang": "cs", "question": "Co je molární objem plynu?", "steps": ["Objem 1 molu plynu.", "Za STP 22,414 l/mol.", "Stejný pro všechny ideální plyny."], "subject": "chemistry", "text": "Answer: Objem 1 molu plynu.\nSteps:\n1. Objem 1 molu plynu.\n2. Za STP 22,414 l/mol.\n3. Stejný pro všechny ideální plyny.", "topic": "stoichiometry"}
{"answer": "There are 5.97 x 10^23 molecules, from 0.992 mol times Avogadro's number.", "choices": null, "id": "che_0605", "kind": "worked_example", "lang": "en", "question": "How many molecules are in 2.00 g of H2 (M = 2.016 g/mol)?", "steps": ["Moles = 2.00/2.016 = 0.992.", "Multiply: 0.992 x 6.022 x 10^23.", "N = 5.97 x 10^23."], "subject": "chemistry", "text": "Answer: 5.97 x 10^23.\nSteps:\n1. Moles = 2.00/2.016 = 0.992.\n2. Multiply: 0.992 x 6.022 x 10^23.\n3. N = 5.97 x 10^23.", "topic": "stoichiometry"}
{"answer": "Calcium hydroxide totals 74.10 g/mol from Ca, 2 O, and 2 H.", "choices": {"A": "74.10 g/mol", "B": "57.09 g/mol", "C": "100.09 g/mol", "D": "40.08 g/mol"}, "id": "che_0606", "kind": "multiple_choice", "lang": "en", "question": "What is the molar mass of Ca(OH)2?", "steps": ["40.08 + 2x16.00 + 2x1.008.", "Total 74.10.", "Select option A."], "subject": "chemistry", "text": "Answer: 74.10 g/mol.\nSteps:\n1. 40.08 + 2x16.00 + 2x1.008.\n2. Total 74.10.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "The gravimetric factor converts precipitate mass to analyte mass via molar mass ratio.", "choices": null, "id": "che_0607", "kind": "concept", "lang": "en", "question": "What is a gravimetric factor?", "steps": ["Weigh a precipitate.", "Ratio of molar masses.", "Multiply to get analyte."], "subject": "chemistry", "text": "Answer: Precipitate-to-analyte ratio.\nSteps:\n1. Weigh a precipitate.\n2. Ratio of molar masses.\n3. Multiply to get analyte.", "topic": "stoichiometry"}
{"answer": "The chloride mass is 70.90 g, from 2.00 mol times 35.45 g/mol.", "choices": null, "id": "che_0608", "kind": "worked_example", "lang": "en", "question": "2.00 mol of AgCl precipitates. What mass of Cl does it hold?", "steps": ["Each AgCl has 1 Cl.", "Moles Cl = 2.00.", "Mass = 2.00 x 35.45 = 70.90 g."], "subject": "chemistry", "text": "Answer: 70.90 g.\nSteps:\n1. Each AgCl has 1 Cl.\n2. Moles Cl = 2.00.\n3. Mass = 2.00 x 35.45 = 70.90 g.", "topic": "stoichiometry"}
{"answer": "Hmotnost je 112,04 g, protože 4 krát 28,01 se rovná 112,04.", "choices": null, "id": "che_0609", "kind": "worked_example", "lang": "cs", "question": "Jaká je hmotnost 4 molů CO (M = 28,01 g/mol)?", "steps": ["Napiš vzorec: m = 4 x 28,01.", "Vynásob.", "m = 112,04 g."], "subject": "chemistry", "text": "Answer: 112,04 g.\nSteps:\n1. Napiš vzorec: m = 4 x 28,01.\n2. Vynásob.\n3. m = 112,04 g.", "topic": "stoichiometry"}
{"answer": "The balanced equation is 2Fe + 3Cl2 -> 2FeCl3.", "choices": {"A": "1, 3, 2", "B": "2, 3, 2", "C": "2, 1, 2", "D": "1, 1, 1"}, "id": "che_0610", "kind": "multiple_choice", "lang": "en", "question": "What coefficients balance Fe + Cl2 -> FeCl3?", "steps": ["Fe: 2 each side.", "Cl: 6 each side.", "Select option B."], "subject": "chemistry", "text": "Answer: 2, 3, 2.\nSteps:\n1. Fe: 2 each side.\n2. Cl: 6 each side.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "One mole of O2 is needed, from 0.5 mol CH4 times the 2/1 ratio.", "choices": null, "id": "che_0611", "kind": "worked_example", "lang": "en", "question": "How much O2 burns 0.50 mol of CH4 (CH4 + 2O2 -> CO2 + 2H2O)?", "steps": ["Ratio O2:CH4 = 2:1.", "Multiply: 0.50 x 2.", "O2 = 1.00 mol."], "subject": "chemistry", "text": "Answer: 1.00 mol.\nSteps:\n1. Ratio O2:CH4 = 2:1.\n2. Multiply: 0.50 x 2.\n3. O2 = 1.00 mol.", "topic": "stoichiometry"}
{"answer": "Side reactions consume reactants into unwanted products, cutting the main yield.", "choices": null, "id": "che_0612", "kind": "concept", "lang": "en", "question": "Why do side reactions lower yield?", "steps": ["Reactants split pathways.", "Less goes to product.", "Yield falls below theory."], "subject": "chemistry", "text": "Answer: Reactants diverted elsewhere.\nSteps:\n1. Reactants split pathways.\n2. Less goes to product.\n3. Yield falls below theory.", "topic": "stoichiometry"}
{"answer": "Hydrogen limits because 2 mol H2 needs only 1 mol O2, leaving O2 over.", "choices": {"A": "H2 limits", "B": "O2 limits", "C": "Neither limits", "D": "Both limit"}, "id": "che_0613", "kind": "multiple_choice", "lang": "en", "question": "With 2 mol H2 and 2 mol O2 for 2H2 + O2 -> 2H2O, what limits?", "steps": ["2 H2 needs 1 O2.", "O2 is in excess.", "Select option A."], "subject": "chemistry", "text": "Answer: H2 limits.\nSteps:\n1. 2 H2 needs 1 O2.\n2. O2 is in excess.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "Teoretický výtěžek je maximální množství produktu ze stechiometrie.", "choices": null, "id": "che_0614", "kind": "concept", "lang": "cs", "question": "Co je teoretický výtěžek?", "steps": ["Výpočet z rovnice.", "Předpoklad úplné reakce.", "Skutečnost bývá nižší."], "subject": "chemistry", "text": "Answer: Stechiometrické maximum.\nSteps:\n1. Výpočet z rovnice.\n2. Předpoklad úplné reakce.\n3. Skutečnost bývá nižší.", "topic": "stoichiometry"}
{"answer": "The actual yield is 30 g, from 0.75 times 40 g.", "choices": null, "id": "che_0615", "kind": "worked_example", "lang": "en", "question": "Theoretical yield is 40 g at 75% yield. Find the actual yield.", "steps": ["Write: actual = 0.75 x 40.", "Multiply.", "Actual = 30 g."], "subject": "chemistry", "text": "Answer: 30 g.\nSteps:\n1. Write: actual = 0.75 x 40.\n2. Multiply.\n3. Actual = 30 g.", "topic": "stoichiometry"}
{"answer": "The molarity is 0.20 M, from 0.0500 mol divided by 0.250 L.", "choices": {"A": "0.02 M", "B": "0.50 M", "C": "5.0 M", "D": "0.20 M"}, "id": "che_0616", "kind": "multiple_choice", "lang": "en", "question": "What is the molarity of 0.0500 mol in 250 mL?", "steps": ["Convert: 250 mL = 0.250 L.", "Divide: 0.0500/0.250.", "Select option D."], "subject": "chemistry", "text": "Answer: 0.20 M.\nSteps:\n1. Convert: 250 mL = 0.250 L.\n2. Divide: 0.0500/0.250.\n3. Select option D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "Dilute to 400 mL total, since 50 x 4.0 / 0.50 = 400 mL.", "choices": null, "id": "che_0617", "kind": "worked_example", "lang": "en", "question": "How to dilute 50 mL of 4.0 M stock to 0.50 M?", "steps": ["Use M1V1 = M2V2.", "V2 = 50 x 4.0/0.50 = 400 mL.", "Add 350 mL solvent."], "subject": "chemistry", "text": "Answer: Dilute to 400 mL.\nSteps:\n1. Use M1V1 = M2V2.\n2. V2 = 50 x 4.0/0.50 = 400 mL.\n3. Add 350 mL solvent.", "topic": "stoichiometry"}
{"answer": "Je to 0,2 molu, protože 0,1 krát 2 se rovná 0,2.", "choices": null, "id": "che_0618", "kind": "worked_example", "lang": "cs", "question": "Kolik molů je ve 100 ml 2M roztoku?", "steps": ["Převeď objem: 0,1 l.", "Vynásob: 0,1 x 2.", "n = 0,2 mol."], "subject": "chemistry", "text": "Answer: 0,2 mol.\nSteps:\n1. Převeď objem: 0,1 l.\n2. Vynásob: 0,1 x 2.\n3. n = 0,2 mol.", "topic": "stoichiometry"}
{"answer": "Carbon dioxide density is 1.96 g/L, from 44.01 g divided by 22.414 L.", "choices": {"A": "1.25 g/L", "B": "1.96 g/L", "C": "0.98 g/L", "D": "2.50 g/L"}, "id": "che_0619", "kind": "multiple_choice", "lang": "en", "question": "What is the density of CO2 gas at STP?", "steps": ["Mass of 1 mol = 44.01 g.", "Divide: 44.01/22.414.", "Select option B."], "subject": "chemistry", "text": "Answer: 1.96 g/L.\nSteps:\n1. Mass of 1 mol = 44.01 g.\n2. Divide: 44.01/22.414.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Ammonia and water form two conjugate pairs: NH4+/NH3 and H2O/OH-.", "choices": null, "id": "che_0620", "kind": "concept", "lang": "en", "question": "What conjugate pairs appear in NH3 + H2O <-> NH4+ + OH-?", "steps": ["NH4+ pairs with NH3.", "H2O pairs with OH-.", "Each differs by one H+."], "subject": "chemistry", "text": "Answer: NH4+/NH3 and H2O/OH-.\nSteps:\n1. NH4+ pairs with NH3.\n2. H2O pairs with OH-.\n3. Each differs by one H+.", "topic": "acids_bases"}
{"answer": "Removing a proton from water gives hydroxide, OH-.", "choices": {"A": "OH(-)", "B": "H3O(+)", "C": "O2(-)", "D": "H2"}, "id": "che_0621", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate base of H2O?", "steps": ["Remove one H+.", "Left with OH-.", "Select option A."], "subject": "chemistry", "text": "Answer: OH-.\nSteps:\n1. Remove one H+.\n2. Left with OH-.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "The pH is 1.40, from -log(0.040).", "choices": null, "id": "che_0622", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.040 M HBr.", "steps": ["HBr dissociates fully.", "pH = -log(0.040).", "pH = 1.40."], "subject": "chemistry", "text": "Answer: 1.40.\nSteps:\n1. HBr dissociates fully.\n2. pH = -log(0.040).\n3. pH = 1.40.", "topic": "acids_bases"}
{"answer": "Konjugovaný pár tvoří kyselina a zásada lišící se o jeden proton.", "choices": null, "id": "che_0623", "kind": "concept", "lang": "cs", "question": "Co je konjugovaný pár?", "steps": ["Dvě částice, rozdíl H+.", "Příklad: HCl/Cl-.", "Silná kyselina = slabá báze."], "subject": "chemistry", "text": "Answer: Dvojice lišící se o H+.\nSteps:\n1. Dvě částice, rozdíl H+.\n2. Příklad: HCl/Cl-.\n3. Silná kyselina = slabá báze.", "topic": "acids_bases"}
{"answer": "Adding a proton to carbonate gives hydrogen carbonate, HCO3-.", "choices": {"A": "CO2", "B": "HCO3(-)", "C": "H2CO3", "D": "OH(-)"}, "id": "che_0624", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate acid of CO3(2-)?", "steps": ["Add one H+.", "Result is HCO3-.", "Select option B."], "subject": "chemistry", "text": "Answer: HCO3-.\nSteps:\n1. Add one H+.\n2. Result is HCO3-.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "Hydroxide concentration is 3.16 x 10^-3 M, from pOH = 14 - 11.5 = 2.5.", "choices": null, "id": "che_0625", "kind": "worked_example", "lang": "en", "question": "A solution has pH 11.50. Compute [OH-].", "steps": ["pOH = 14 - 11.50 = 2.50.", "Write: [OH-] = 10^(-2.50).", "[OH-] = 3.16 x 10^-3 M."], "subject": "chemistry", "text": "Answer: 3.16 x 10^-3 M.\nSteps:\n1. pOH = 14 - 11.50 = 2.50.\n2. Write: [OH-] = 10^(-2.50).\n3. [OH-] = 3.16 x 10^-3 M.", "topic": "acids_bases"}
{"answer": "Group 1 hydroxides and heavy Group 2 hydroxides are strong bases.", "choices": null, "id": "che_0626", "kind": "concept", "lang": "en", "question": "Which hydroxides are strong bases?", "steps": ["Group 1: NaOH, KOH.", "Heavy Group 2: Ca, Sr, Ba.", "They dissociate fully."], "subject": "chemistry", "text": "Answer: Group 1 and heavy Group 2.\nSteps:\n1. Group 1: NaOH, KOH.\n2. Heavy Group 2: Ca, Sr, Ba.\n3. They dissociate fully.", "topic": "acids_bases"}
{"answer": "The pH is 12.30, from [OH-] = 0.020 M giving pOH 1.70.", "choices": null, "id": "che_0627", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.010 M Ca(OH)2.", "steps": ["[OH-] = 2 x 0.010 = 0.020 M.", "pOH = -log(0.020) = 1.70.", "pH = 14 - 1.70 = 12.30."], "subject": "chemistry", "text": "Answer: 12.30.\nSteps:\n1. [OH-] = 2 x 0.010 = 0.020 M.\n2. pOH = -log(0.020) = 1.70.\n3. pH = 14 - 1.70 = 12.30.", "topic": "acids_bases"}
{"answer": "Each Ca(OH)2 releases two hydroxide ions.", "choices": {"A": "1", "B": "3", "C": "2", "D": "0"}, "id": "che_0628", "kind": "multiple_choice", "lang": "en", "question": "How many OH- does one Ca(OH)2 release?", "steps": ["Formula has two OH.", "Both release.", "Select option C."], "subject": "chemistry", "text": "Answer: 2.\nSteps:\n1. Formula has two OH.\n2. Both release.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "pOH je 1,30, protože -log(0,05) = 1,30.", "choices": null, "id": "che_0629", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pOH roztoku 0,05 M NaOH.", "steps": ["NaOH disociuje plně.", "pOH = -log(0,05).", "pOH = 1,30."], "subject": "chemistry", "text": "Answer: 1,30.\nSteps:\n1. NaOH disociuje plně.\n2. pOH = -log(0,05).\n3. pOH = 1,30.", "topic": "acids_bases"}
{"answer": "Acid rain forms when SO2 and NOx dissolve into sulfuric and nitric acids.", "choices": null, "id": "che_0630", "kind": "concept", "lang": "en", "question": "What chemistry causes acid rain?", "steps": ["Burning releases SO2, NOx.", "They oxidize and dissolve.", "Rain pH drops below 5.6."], "subject": "chemistry", "text": "Answer: SO2 and NOx acids.\nSteps:\n1. Burning releases SO2, NOx.\n2. They oxidize and dissolve.\n3. Rain pH drops below 5.6.", "topic": "acids_bases"}
{"answer": "Rain below pH 5.6 counts as acid rain.", "choices": {"A": "7.0", "B": "8.0", "C": "6.5", "D": "5.6"}, "id": "che_0631", "kind": "multiple_choice", "lang": "en", "question": "Below what pH is rain called acid rain?", "steps": ["Natural rain is ~5.6.", "Lower means polluted.", "Select option D."], "subject": "chemistry", "text": "Answer: 5.6.\nSteps:\n1. Natural rain is ~5.6.\n2. Lower means polluted.\n3. Select option D.\nAnswer: (D)", "topic": "acids_bases"}
{"answer": "Exactly 40.0 mL of NaOH is needed, matching 4.00 mmol of H+.", "choices": null, "id": "che_0632", "kind": "worked_example", "lang": "en", "question": "What volume of 0.100 M NaOH neutralizes 10.0 mL of 0.200 M H2SO4?", "steps": ["H+ = 2 x 10.0 x 0.200 = 4.00 mmol.", "Same mmol NaOH needed.", "V = 4.00/0.100 = 40.0 mL."], "subject": "chemistry", "text": "Answer: 40.0 mL.\nSteps:\n1. H+ = 2 x 10.0 x 0.200 = 4.00 mmol.\n2. Same mmol NaOH needed.\n3. V = 4.00/0.100 = 40.0 mL.", "topic": "acids_bases"}
{"answer": "Diprotic titrations show two endpoints, one per proton.", "choices": null, "id": "che_0633", "kind": "concept", "lang": "en", "question": "Why do diprotic titrations have two endpoints?", "steps": ["First proton neutralized.", "Then the second.", "Two jumps appear."], "subject": "chemistry", "text": "Answer: One endpoint per proton.\nSteps:\n1. First proton neutralized.\n2. Then the second.\n3. Two jumps appear.", "topic": "acids_bases"}
{"answer": "Kyselý déšť je déšť s pH pod 5,6 kvůli oxidům síry a dusíku.", "choices": null, "id": "che_0634", "kind": "concept", "lang": "cs", "question": "Co je kyselý déšť?", "steps": ["Emise SO2 a NOx.", "Vznik kyselin v atmosféře.", "pH pod 5,6."], "subject": "chemistry", "text": "Answer: Déšť s pH pod 5,6.\nSteps:\n1. Emise SO2 a NOx.\n2. Vznik kyselin v atmosféře.\n3. pH pod 5,6.", "topic": "acids_bases"}
{"answer": "Phenol red is yellow in acid and red in base.", "choices": {"A": "Yellow acid, red base", "B": "Red acid, yellow base", "C": "Blue both", "D": "Pink both"}, "id": "che_0635", "kind": "multiple_choice", "lang": "en", "question": "How does phenol red change color?", "steps": ["Acid form yellow.", "Base form red.", "Select option A."], "subject": "chemistry", "text": "Answer: Yellow acid, red base.\nSteps:\n1. Acid form yellow.\n2. Base form red.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "The concentration is 5.01 x 10^-7 M, from 10 raised to -6.30.", "choices": null, "id": "che_0636", "kind": "worked_example", "lang": "en", "question": "A solution has pH 6.30. Compute [H+].", "steps": ["Write: [H+] = 10^(-6.30).", "Evaluate.", "[H+] = 5.01 x 10^-7 M."], "subject": "chemistry", "text": "Answer: 5.01 x 10^-7 M.\nSteps:\n1. Write: [H+] = 10^(-6.30).\n2. Evaluate.\n3. [H+] = 5.01 x 10^-7 M.", "topic": "acids_bases"}
{"answer": "pH je 3, protože -log(0,001) = 3.", "choices": null, "id": "che_0637", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,001 M HNO3.", "steps": ["HNO3 disociuje plně.", "pH = -log(0,001).", "pH = 3."], "subject": "chemistry", "text": "Answer: 3.\nSteps:\n1. HNO3 disociuje plně.\n2. pH = -log(0,001).\n3. pH = 3.", "topic": "acids_bases"}
{"answer": "Carbonate hydrolyzes to make OH-, so the solution is basic.", "choices": {"A": "Acidic", "B": "Neutral", "C": "Basic", "D": "Cannot tell"}, "id": "che_0638", "kind": "multiple_choice", "lang": "en", "question": "Is Na2CO3 solution acidic or basic?", "steps": ["CO3(2-) is base of weak acid.", "It makes OH-.", "Select option C."], "subject": "chemistry", "text": "Answer: Basic.\nSteps:\n1. CO3(2-) is base of weak acid.\n2. It makes OH-.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "Halogens are -1 except with oxygen or more electronegative halogens.", "choices": null, "id": "che_0639", "kind": "concept", "lang": "en", "question": "What oxidation states do halogens take?", "steps": ["Normal rule: -1.", "With O: positive states.", "Example: Cl in ClO3- is +5."], "subject": "chemistry", "text": "Answer: Usually -1, positive with O.\nSteps:\n1. Normal rule: -1.\n2. With O: positive states.\n3. Example: Cl in ClO3- is +5.", "topic": "redox"}
{"answer": "Chlorine is +1, since +1 + Cl + (-2) = 0.", "choices": {"A": "-1", "B": "0", "C": "+1", "D": "+3"}, "id": "che_0640", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of Cl in HClO?", "steps": ["H +1, O -2.", "Solve: 1 + Cl - 2 = 0.", "Cl = +1; select C."], "subject": "chemistry", "text": "Answer: +1.\nSteps:\n1. H +1, O -2.\n2. Solve: 1 + Cl - 2 = 0.\n3. Cl = +1; select C.\nAnswer: (C)", "topic": "redox"}
{"answer": "Silicon is +4, since Si + 2(-2) = 0 gives Si = +4.", "choices": null, "id": "che_0641", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of Si in SiO2.", "steps": ["Assign O -2.", "Equation: Si - 4 = 0.", "Si = +4."], "subject": "chemistry", "text": "Answer: +4.\nSteps:\n1. Assign O -2.\n2. Equation: Si - 4 = 0.\n3. Si = +4.", "topic": "redox"}
{"answer": "Oxidovadlo je látka, která přijímá elektrony a sama se redukuje.", "choices": null, "id": "che_0642", "kind": "concept", "lang": "cs", "question": "Co je oxidovadlo?", "steps": ["Přijímá elektrony.", "Samo se redukuje.", "Příklad: O2, Cl2."], "subject": "chemistry", "text": "Answer: Příjemce elektronů.\nSteps:\n1. Přijímá elektrony.\n2. Samo se redukuje.\n3. Příklad: O2, Cl2.", "topic": "redox"}
{"answer": "Hydrogen goes from 0 to +1, so it is oxidized.", "choices": {"A": "CuO", "B": "H2", "C": "Cu", "D": "O"}, "id": "che_0643", "kind": "multiple_choice", "lang": "en", "question": "In CuO + H2 -> Cu + H2O, what is oxidized?", "steps": ["H goes 0 to +1.", "That is oxidation.", "Select option B."], "subject": "chemistry", "text": "Answer: H2.\nSteps:\n1. H goes 0 to +1.\n2. That is oxidation.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "The balanced equation is 4P + 5O2 -> 2P2O5.", "choices": null, "id": "che_0644", "kind": "worked_example", "lang": "en", "question": "Balance: P + O2 -> P2O5.", "steps": ["Balance P with 2 P2O5 and 4 P.", "Count O: 10 each side.", "Use 5 O2: 4P + 5O2 -> 2P2O5."], "subject": "chemistry", "text": "Answer: 4P + 5O2 -> 2P2O5.\nSteps:\n1. Balance P with 2 P2O5 and 4 P.\n2. Count O: 10 each side.\n3. Use 5 O2: 4P + 5O2 -> 2P2O5.", "topic": "redox"}
{"answer": "Permanganate titrations use purple MnO4- that turns colorless as Mn2+ at the endpoint.", "choices": null, "id": "che_0645", "kind": "concept", "lang": "en", "question": "How does permanganate titration work?", "steps": ["MnO4- oxidizes analyte.", "Purple fades to colorless.", "First pink marks endpoint."], "subject": "chemistry", "text": "Answer: Purple to colorless endpoint.\nSteps:\n1. MnO4- oxidizes analyte.\n2. Purple fades to colorless.\n3. First pink marks endpoint.", "topic": "redox"}
{"answer": "Three electrons are gained as chromium drops from +6 to +3.", "choices": null, "id": "che_0646", "kind": "worked_example", "lang": "en", "question": "How many electrons are gained in Cr(+6) -> Cr(+3)?", "steps": ["Change: +6 to +3.", "Difference = 3 down.", "Electrons gained = 3."], "subject": "chemistry", "text": "Answer: 3 electrons.\nSteps:\n1. Change: +6 to +3.\n2. Difference = 3 down.\n3. Electrons gained = 3.", "topic": "redox"}
{"answer": "Iodide gives up electrons most easily among the halides.", "choices": {"A": "F(-)", "B": "Cl(-)", "C": "Br(-)", "D": "I(-)"}, "id": "che_0647", "kind": "multiple_choice", "lang": "en", "question": "Which halide is the strongest reducing agent?", "steps": ["Largest ion oxidizes easiest.", "I- tops the series.", "Select option D."], "subject": "chemistry", "text": "Answer: I-.\nSteps:\n1. Largest ion oxidizes easiest.\n2. I- tops the series.\n3. Select option D.\nAnswer: (D)", "topic": "redox"}
{"answer": "Mangan má oxidační číslo +4, protože Mn + 2(-2) = 0.", "choices": null, "id": "che_0648", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo manganu v MnO2.", "steps": ["Přiřaď O -2.", "Rovnice: Mn - 4 = 0.", "Mn = +4."], "subject": "chemistry", "text": "Answer: +4.\nSteps:\n1. Přiřaď O -2.\n2. Rovnice: Mn - 4 = 0.\n3. Mn = +4.", "topic": "redox"}
{"answer": "Aluminum forms a tight oxide skin that blocks further attack.", "choices": null, "id": "che_0649", "kind": "concept", "lang": "en", "question": "Why does aluminum resist corrosion?", "steps": ["Surface oxidizes fast.", "Dense Al2O3 layer forms.", "Layer seals the metal."], "subject": "chemistry", "text": "Answer: Protective oxide layer.\nSteps:\n1. Surface oxidizes fast.\n2. Dense Al2O3 layer forms.\n3. Layer seals the metal.", "topic": "redox"}
{"answer": "A sealing oxide layer stops aluminum corrosion.", "choices": {"A": "Oxide layer", "B": "Paint only", "C": "Oil coating", "D": "Noble metal"}, "id": "che_0650", "kind": "multiple_choice", "lang": "en", "question": "What protects aluminum from corrosion?", "steps": ["Al2O3 seals surface.", "Eliminate paint, oil, noble.", "Select option A."], "subject": "chemistry", "text": "Answer: Oxide layer.\nSteps:\n1. Al2O3 seals surface.\n2. Eliminate paint, oil, noble.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "The balanced equation is C2H4 + 3O2 -> 2CO2 + 2H2O.", "choices": null, "id": "che_0651", "kind": "worked_example", "lang": "en", "question": "Balance: C2H4 + O2 -> CO2 + H2O.", "steps": ["Balance C with 2 CO2.", "Balance H with 2 H2O.", "Balance O with 3 O2."], "subject": "chemistry", "text": "Answer: C2H4 + 3O2 -> 2CO2 + 2H2O.\nSteps:\n1. Balance C with 2 CO2.\n2. Balance H with 2 H2O.\n3. Balance O with 3 O2.", "topic": "redox"}
{"answer": "Elektrodový děj je oxidace na anodě nebo redukce na katodě.", "choices": null, "id": "che_0652", "kind": "concept", "lang": "cs", "question": "Co je elektrodový děj?", "steps": ["Na anodě oxidace.", "Na katodě redukce.", "Elektrony tečou vnějškem."], "subject": "chemistry", "text": "Answer: Oxidace či redukce na elektrodě.\nSteps:\n1. Na anodě oxidace.\n2. Na katodě redukce.\n3. Elektrony tečou vnějškem.", "topic": "redox"}
{"answer": "Sulfur is -2, since 2(+1) + S = 0 gives S = -2.", "choices": {"A": "-2", "B": "0", "C": "+2", "D": "+4"}, "id": "che_0653", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of sulfur in H2S?", "steps": ["H is +1 each.", "Solve: 2 + S = 0.", "S = -2; select A."], "subject": "chemistry", "text": "Answer: -2.\nSteps:\n1. H is +1 each.\n2. Solve: 2 + S = 0.\n3. S = -2; select A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Combustion analysis burns a sample so CO2 and H2O reveal C and H content.", "choices": null, "id": "che_0654", "kind": "concept", "lang": "en", "question": "How does combustion analysis find formulas?", "steps": ["Burn sample in O2.", "Weigh CO2 and H2O.", "Back-calculate C and H."], "subject": "chemistry", "text": "Answer: Burn, weigh, back-calculate.\nSteps:\n1. Burn sample in O2.\n2. Weigh CO2 and H2O.\n3. Back-calculate C and H.", "topic": "redox"}
{"answer": "Vyčíslená rovnice je 2HgO -> 2Hg + O2.", "choices": null, "id": "che_0655", "kind": "worked_example", "lang": "cs", "question": "Vyčísli: HgO -> Hg + O2.", "steps": ["Kyslík: 2 HgO a 1 O2.", "Rtuť: 2 Hg.", "Výsledek: 2HgO -> 2Hg + O2."], "subject": "chemistry", "text": "Answer: 2HgO -> 2Hg + O2.\nSteps:\n1. Kyslík: 2 HgO a 1 O2.\n2. Rtuť: 2 Hg.\n3. Výsledek: 2HgO -> 2Hg + O2.", "topic": "redox"}
{"answer": "Each nitrogen averages +1, since 2N + (-2) = 0.", "choices": {"A": "0", "B": "+1", "C": "+2", "D": "-1"}, "id": "che_0656", "kind": "multiple_choice", "lang": "en", "question": "What is nitrogen's oxidation state in N2O?", "steps": ["O is -2.", "Solve: 2N - 2 = 0.", "N = +1; select B."], "subject": "chemistry", "text": "Answer: +1.\nSteps:\n1. O is -2.\n2. Solve: 2N - 2 = 0.\n3. N = +1; select B.\nAnswer: (B)", "topic": "redox"}
{"answer": "Two electrons transfer: each Na loses 1 and Cl2 gains 2.", "choices": null, "id": "che_0657", "kind": "worked_example", "lang": "en", "question": "How many electrons transfer in 2Na + Cl2 -> 2NaCl?", "steps": ["Each Na: 0 -> +1, loses 1.", "Two Na lose 2 total.", "Cl2 gains 2; transfer = 2 e-."], "subject": "chemistry", "text": "Answer: 2 electrons.\nSteps:\n1. Each Na: 0 -> +1, loses 1.\n2. Two Na lose 2 total.\n3. Cl2 gains 2; transfer = 2 e-.", "topic": "redox"}
{"answer": "The zeroth law states bodies in thermal equilibrium with a third share a temperature.", "choices": null, "id": "che_0658", "kind": "concept", "lang": "en", "question": "What is the zeroth law of thermodynamics?", "steps": ["A matches C in temperature.", "B matches C too.", "Then A matches B."], "subject": "chemistry", "text": "Answer: Shared temperature transitive.\nSteps:\n1. A matches C in temperature.\n2. B matches C too.\n3. Then A matches B.", "topic": "thermochemistry"}
{"answer": "The zeroth law founds the temperature concept and thermometry.", "choices": {"A": "Temperature", "B": "Pressure", "C": "Entropy", "D": "Enthalpy"}, "id": "che_0659", "kind": "multiple_choice", "lang": "en", "question": "What concept does the zeroth law define?", "steps": ["Equilibrium transitivity.", "That defines temperature.", "Select option A."], "subject": "chemistry", "text": "Answer: Temperature.\nSteps:\n1. Equilibrium transitivity.\n2. That defines temperature.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "The internal energy change is +1000 J, from +800 plus +200 J.", "choices": null, "id": "che_0660", "kind": "worked_example", "lang": "en", "question": "A system absorbs 800 J of heat while 200 J of work is done on it. Find ΔU.", "steps": ["Write: ΔU = 800 + 200.", "Add.", "ΔU = +1000 J."], "subject": "chemistry", "text": "Answer: +1000 J.\nSteps:\n1. Write: ΔU = 800 + 200.\n2. Add.\n3. ΔU = +1000 J.", "topic": "thermochemistry"}
{"answer": "Tepelná rovnováha znamená stejné teploty a nulový čistý tok tepla.", "choices": null, "id": "che_0661", "kind": "concept", "lang": "cs", "question": "Co je tepelná rovnováha?", "steps": ["Tělesa v kontaktu.", "Teploty se vyrovnají.", "Tok tepla ustane."], "subject": "chemistry", "text": "Answer: Stejné teploty, žádný tok.\nSteps:\n1. Tělesa v kontaktu.\n2. Teploty se vyrovnají.\n3. Tok tepla ustane.", "topic": "thermochemistry"}
{"answer": "Heat always flows spontaneously from hot bodies to cold ones.", "choices": {"A": "Cold to hot", "B": "Hot to cold", "C": "Never flows", "D": "Sideways only"}, "id": "che_0662", "kind": "multiple_choice", "lang": "en", "question": "Which way does heat flow spontaneously?", "steps": ["Second law direction.", "Hot loses, cold gains.", "Select option B."], "subject": "chemistry", "text": "Answer: Hot to cold.\nSteps:\n1. Second law direction.\n2. Hot loses, cold gains.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "The heat is 19,250 J, from 500 x 0.385 x 100.", "choices": null, "id": "che_0663", "kind": "worked_example", "lang": "en", "question": "How much heat warms 500 g of copper by 100 C (c = 0.385 J/gC)?", "steps": ["Write: q = 500 x 0.385 x 100.", "Multiply.", "q = 19,250 J."], "subject": "chemistry", "text": "Answer: 19,250 J.\nSteps:\n1. Write: q = 500 x 0.385 x 100.\n2. Multiply.\n3. q = 19,250 J.", "topic": "thermochemistry"}
{"answer": "Heat moves by conduction through contact, convection by flow, and radiation by waves.", "choices": null, "id": "che_0664", "kind": "concept", "lang": "en", "question": "What are the three heat transfer methods?", "steps": ["Conduction via contact.", "Convection via fluid flow.", "Radiation via waves."], "subject": "chemistry", "text": "Answer: Conduction, convection, radiation.\nSteps:\n1. Conduction via contact.\n2. Convection via fluid flow.\n3. Radiation via waves.", "topic": "thermochemistry"}
{"answer": "Melting needs 18.03 kJ, from 3.00 mol times 6.01 kJ/mol.", "choices": null, "id": "che_0665", "kind": "worked_example", "lang": "en", "question": "How much heat melts 54.0 g of ice (ΔHfus = 6.01 kJ/mol)?", "steps": ["Moles = 54.0/18.015 = 3.00.", "Multiply: 3.00 x 6.01.", "Heat = 18.03 kJ."], "subject": "chemistry", "text": "Answer: 18.03 kJ.\nSteps:\n1. Moles = 54.0/18.015 = 3.00.\n2. Multiply: 3.00 x 6.01.\n3. Heat = 18.03 kJ.", "topic": "thermochemistry"}
{"answer": "Condensation forms liquid bonds and releases heat, so it is exothermic.", "choices": {"A": "Exothermic", "B": "Endothermic", "C": "Athermal", "D": "Isolated"}, "id": "che_0666", "kind": "multiple_choice", "lang": "en", "question": "Is condensation endothermic or exothermic?", "steps": ["Bonds form going liquid.", "Forming releases energy.", "Select option A."], "subject": "chemistry", "text": "Answer: Exothermic.\nSteps:\n1. Bonds form going liquid.\n2. Forming releases energy.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "K roztátí je třeba 30,05 kJ, protože 5 molů krát 6,01 se rovná 30,05.", "choices": null, "id": "che_0667", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla roztaví 90 g ledu (ΔH = 6,01 kJ/mol)?", "steps": ["Moly = 90/18 = 5.", "Vynásob: 5 x 6,01.", "Teplo = 30,05 kJ."], "subject": "chemistry", "text": "Answer: 30,05 kJ.\nSteps:\n1. Moly = 90/18 = 5.\n2. Vynásob: 5 x 6,01.\n3. Teplo = 30,05 kJ.", "topic": "thermochemistry"}
{"answer": "Enthalpy diagrams plot energy levels of reactants and products with ΔH as the gap.", "choices": null, "id": "che_0668", "kind": "concept", "lang": "en", "question": "What is an enthalpy diagram?", "steps": ["Levels for reactants.", "Levels for products.", "Gap equals ΔH."], "subject": "chemistry", "text": "Answer: Energy levels with ΔH gap.\nSteps:\n1. Levels for reactants.\n2. Levels for products.\n3. Gap equals ΔH.", "topic": "thermochemistry"}
{"answer": "Endothermic products sit above reactants on the energy diagram.", "choices": {"A": "Below reactants", "B": "Equal to reactants", "C": "Above reactants", "D": "At zero"}, "id": "che_0669", "kind": "multiple_choice", "lang": "en", "question": "Where are products on an endothermic diagram?", "steps": ["Endo absorbs energy.", "Products hold more.", "Select option C."], "subject": "chemistry", "text": "Answer: Above reactants.\nSteps:\n1. Endo absorbs energy.\n2. Products hold more.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "Two moles release 200 kJ, double the per-mole ΔH of -100 kJ.", "choices": null, "id": "che_0670", "kind": "worked_example", "lang": "en", "question": "A reaction releases 100 kJ per mole of fuel. How much for 2.00 mol?", "steps": ["Scale: 2.00 x (-100).", "Multiply.", "Heat = -200 kJ."], "subject": "chemistry", "text": "Answer: -200 kJ.\nSteps:\n1. Scale: 2.00 x (-100).\n2. Multiply.\n3. Heat = -200 kJ.", "topic": "thermochemistry"}
{"answer": "Endotermická reakce pohlcuje teplo z okolí a má kladnou změnu entalpie.", "choices": null, "id": "che_0671", "kind": "concept", "lang": "cs", "question": "Co je endotermická reakce?", "steps": ["Pohlcuje teplo.", "ΔH je kladné.", "Příklad: tání ledu."], "subject": "chemistry", "text": "Answer: Reakce pohlcující teplo.\nSteps:\n1. Pohlcuje teplo.\n2. ΔH je kladné.\n3. Příklad: tání ledu.", "topic": "thermochemistry"}
{"answer": "Melting raises disorder, so ΔS is positive.", "choices": {"A": "Negative", "B": "Positive", "C": "Zero", "D": "Undefined"}, "id": "che_0672", "kind": "multiple_choice", "lang": "en", "question": "What is the sign of ΔS for melting ice?", "steps": ["Solid to liquid.", "Disorder rises.", "Select option B."], "subject": "chemistry", "text": "Answer: Positive.\nSteps:\n1. Solid to liquid.\n2. Disorder rises.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "ΔG is -19.6 kJ, from 40 minus 298 x 0.200.", "choices": null, "id": "che_0673", "kind": "worked_example", "lang": "en", "question": "ΔH = +40 kJ and ΔS = +0.200 kJ/K at 298 K. Compute ΔG.", "steps": ["Write: ΔG = 40 - 298 x 0.200.", "Simplify: 40 - 59.6.", "ΔG = -19.6 kJ."], "subject": "chemistry", "text": "Answer: -19.6 kJ.\nSteps:\n1. Write: ΔG = 40 - 298 x 0.200.\n2. Simplify: 40 - 59.6.\n3. ΔG = -19.6 kJ.", "topic": "thermochemistry"}
{"answer": "Entropie vesmíru je součet entropie soustavy a okolí; u samovolných dějů roste.", "choices": null, "id": "che_0674", "kind": "concept", "lang": "cs", "question": "Co je entropie vesmíru?", "steps": ["Soustava plus okolí.", "Samovolné děje ji zvyšují.", "Druhý zákon ji řídí."], "subject": "chemistry", "text": "Answer: Celková entropie děje.\nSteps:\n1. Soustava plus okolí.\n2. Samovolné děje ji zvyšují.\n3. Druhý zákon ji řídí.", "topic": "thermochemistry"}
{"answer": "Positive ΔH needs high T so the -TΔS term can win.", "choices": {"A": "ΔH<0, ΔS>0", "B": "ΔH<0, ΔS<0", "C": "ΔH>0, ΔS<0", "D": "ΔH>0, ΔS>0"}, "id": "che_0675", "kind": "multiple_choice", "lang": "en", "question": "Which signs give spontaneity only at high T?", "steps": ["Need ΔG < 0 via -TΔS.", "Requires ΔS > 0 with ΔH > 0.", "Select option D."], "subject": "chemistry", "text": "Answer: ΔH>0, ΔS>0.\nSteps:\n1. Need ΔG < 0 via -TΔS.\n2. Requires ΔS > 0 with ΔH > 0.\n3. Select option D.\nAnswer: (D)", "topic": "thermochemistry"}
{"answer": "Freezing releases 6.01 kJ per mole, the reverse of fusion.", "choices": null, "id": "che_0676", "kind": "worked_example", "lang": "en", "question": "How much heat is released freezing 1.00 mol of water (ΔHfus = 6.01 kJ/mol)?", "steps": ["Freezing reverses melting.", "Heat = -6.01 kJ/mol.", "Total = -6.01 kJ."], "subject": "chemistry", "text": "Answer: -6.01 kJ.\nSteps:\n1. Freezing reverses melting.\n2. Heat = -6.01 kJ/mol.\n3. Total = -6.01 kJ.", "topic": "thermochemistry"}
{"answer": "Halogen substituents use fluoro-, chloro-, bromo-, and iodo- prefixes.", "choices": null, "id": "che_0677", "kind": "concept", "lang": "en", "question": "What prefixes name halogen substituents?", "steps": ["F gives fluoro.", "Cl gives chloro.", "Br gives bromo, I gives iodo."], "subject": "chemistry", "text": "Answer: Fluoro, chloro, bromo, iodo.\nSteps:\n1. F gives fluoro.\n2. Cl gives chloro.\n3. Br gives bromo, I gives iodo.", "topic": "organic_naming"}
{"answer": "A fluorine substituent is named with the fluoro- prefix.", "choices": {"A": "Fluorite", "B": "Fluoro", "C": "Fluoride", "D": "Fluorine"}, "id": "che_0678", "kind": "multiple_choice", "lang": "en", "question": "What prefix names an F substituent?", "steps": ["Substituent form needed.", "That is fluoro.", "Select option B."], "subject": "chemistry", "text": "Answer: Fluoro.\nSteps:\n1. Substituent form needed.\n2. That is fluoro.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is 1-chloropropane: chlorine on carbon 1.", "choices": null, "id": "che_0679", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2CH2Cl.", "steps": ["Count 3 carbons.", "Cl on carbon 1.", "Name: 1-chloropropane."], "subject": "chemistry", "text": "Answer: 1-chloropropane.\nSteps:\n1. Count 3 carbons.\n2. Cl on carbon 1.\n3. Name: 1-chloropropane.", "topic": "organic_naming"}
{"answer": "Poloha substituentu se značí číslem uhlíku před názvem.", "choices": null, "id": "che_0680", "kind": "concept", "lang": "cs", "question": "Jak se značí poloha substituentu?", "steps": ["Očísluj řetězec.", "Číslo před název.", "Příklad: 2-chlorpropan."], "subject": "chemistry", "text": "Answer: Číslem před názvem.\nSteps:\n1. Očísluj řetězec.\n2. Číslo před název.\n3. Příklad: 2-chlorpropan.", "topic": "organic_naming"}
{"answer": "1,2-dichloroethane has two carbons, each bearing one chlorine.", "choices": {"A": "2", "B": "1", "C": "3", "D": "4"}, "id": "che_0681", "kind": "multiple_choice", "lang": "en", "question": "How many carbons are in 1,2-dichloroethane?", "steps": ["Ethane root = 2.", "Dichloro adds none.", "Select option A."], "subject": "chemistry", "text": "Answer: 2.\nSteps:\n1. Ethane root = 2.\n2. Dichloro adds none.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "The name is propan-2-ol: -OH on carbon 2 of three.", "choices": null, "id": "che_0682", "kind": "worked_example", "lang": "en", "question": "Name CH3CH(OH)CH3.", "steps": ["Count 3 carbons.", "-OH on carbon 2.", "Name: propan-2-ol."], "subject": "chemistry", "text": "Answer: Propan-2-ol.\nSteps:\n1. Count 3 carbons.\n2. -OH on carbon 2.\n3. Name: propan-2-ol.", "topic": "organic_naming"}
{"answer": "Secondary alcohols have -OH on a carbon with two neighbors; tertiary have three.", "choices": null, "id": "che_0683", "kind": "concept", "lang": "en", "question": "How do secondary and tertiary alcohols differ?", "steps": ["Count carbon neighbors.", "Two means secondary.", "Three means tertiary."], "subject": "chemistry", "text": "Answer: Two versus three neighbors.\nSteps:\n1. Count carbon neighbors.\n2. Two means secondary.\n3. Three means tertiary.", "topic": "organic_naming"}
{"answer": "The name is 2-methylpropan-2-ol: -OH and methyl on carbon 2.", "choices": null, "id": "che_0684", "kind": "worked_example", "lang": "en", "question": "Name (CH3)3COH.", "steps": ["Longest chain: 3 = propane.", "-OH on carbon 2.", "Methyl on carbon 2: 2-methylpropan-2-ol."], "subject": "chemistry", "text": "Answer: 2-methylpropan-2-ol.\nSteps:\n1. Longest chain: 3 = propane.\n2. -OH on carbon 2.\n3. Methyl on carbon 2: 2-methylpropan-2-ol.", "topic": "organic_naming"}
{"answer": "The C-OH carbon has three carbon neighbors, so it is tertiary.", "choices": {"A": "Primary", "B": "Secondary", "C": "Tertiary", "D": "Quaternary"}, "id": "che_0685", "kind": "multiple_choice", "lang": "en", "question": "How is (CH3)3COH classified?", "steps": ["Count neighbors: three.", "Three means tertiary.", "Select option C."], "subject": "chemistry", "text": "Answer: Tertiary.\nSteps:\n1. Count neighbors: three.\n2. Three means tertiary.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "CH3OH je methanol.", "choices": null, "id": "che_0686", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH3OH.", "steps": ["Jeden uhlík.", "Skupina -OH = -ol.", "Název: methanol."], "subject": "chemistry", "text": "Answer: Methanol.\nSteps:\n1. Jeden uhlík.\n2. Skupina -OH = -ol.\n3. Název: methanol.", "topic": "organic_naming"}
{"answer": "Alkene names combine locant, cis/trans tag, and the -ene root.", "choices": null, "id": "che_0687", "kind": "concept", "lang": "en", "question": "How are cis/trans alkenes named fully?", "steps": ["Number the double bond.", "Assign cis or trans.", "Write tag, locant, root."], "subject": "chemistry", "text": "Answer: Tag plus locant plus root.\nSteps:\n1. Number the double bond.\n2. Assign cis or trans.\n3. Write tag, locant, root.", "topic": "organic_naming"}
{"answer": "Trans means the methyl groups sit on opposite sides.", "choices": {"A": "Opposite sides", "B": "Same side", "C": "Ring form", "D": "No geometry"}, "id": "che_0688", "kind": "multiple_choice", "lang": "en", "question": "What does trans-2-butene look like?", "steps": ["Trans means across.", "Groups oppose.", "Select option A."], "subject": "chemistry", "text": "Answer: Opposite sides.\nSteps:\n1. Trans means across.\n2. Groups oppose.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "The name is but-1-ene: double bond starting at carbon 1.", "choices": null, "id": "che_0689", "kind": "worked_example", "lang": "en", "question": "Name CH2=CHCH2CH3.", "steps": ["Count 4 carbons.", "Double bond at carbon 1.", "Name: but-1-ene."], "subject": "chemistry", "text": "Answer: But-1-ene.\nSteps:\n1. Count 4 carbons.\n2. Double bond at carbon 1.\n3. Name: but-1-ene.", "topic": "organic_naming"}
{"answer": "Alkyne locants mark where the triple bond starts with lowest numbers.", "choices": null, "id": "che_0690", "kind": "concept", "lang": "en", "question": "How do alkyne locants work?", "steps": ["Find triple bond.", "Number lowest there.", "Example: but-2-yne."], "subject": "chemistry", "text": "Answer: Lowest number at triple bond.\nSteps:\n1. Find triple bond.\n2. Number lowest there.\n3. Example: but-2-yne.", "topic": "organic_naming"}
{"answer": "Trojná vazba se v názvu značí koncovkou -yn s číslem polohy.", "choices": null, "id": "che_0691", "kind": "concept", "lang": "cs", "question": "Co značí trojná vazba v názvu?", "steps": ["Koncovka -yn.", "Číslo polohy.", "Příklad: but-2-yn."], "subject": "chemistry", "text": "Answer: Koncovku -yn s číslem.\nSteps:\n1. Koncovka -yn.\n2. Číslo polohy.\n3. Příklad: but-2-yn.", "topic": "organic_naming"}
{"answer": "The locant 2 marks the triple bond starting at carbon 2.", "choices": {"A": "Carbon 1", "B": "Carbon 2", "C": "Carbon 3", "D": "Carbon 4"}, "id": "che_0692", "kind": "multiple_choice", "lang": "en", "question": "Where is the triple bond in but-2-yne?", "steps": ["Read the locant: 2.", "Bond starts at carbon 2.", "Select option B."], "subject": "chemistry", "text": "Answer: Carbon 2.\nSteps:\n1. Read the locant: 2.\n2. Bond starts at carbon 2.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is ethylbenzene: an ethyl group on benzene.", "choices": null, "id": "che_0693", "kind": "worked_example", "lang": "en", "question": "Name C6H5CH2CH3.", "steps": ["Benzene ring present.", "Ethyl substituent attached.", "Name: ethylbenzene."], "subject": "chemistry", "text": "Answer: Ethylbenzene.\nSteps:\n1. Benzene ring present.\n2. Ethyl substituent attached.\n3. Name: ethylbenzene.", "topic": "organic_naming"}
{"answer": "CH≡CH je ethyn.", "choices": null, "id": "che_0694", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH≡CH.", "steps": ["Dva uhlíky.", "Trojná vazba = -yn.", "Název: ethyn."], "subject": "chemistry", "text": "Answer: Ethyn.\nSteps:\n1. Dva uhlíky.\n2. Trojná vazba = -yn.\n3. Název: ethyn.", "topic": "organic_naming"}
{"answer": "Acid chlorides replace -OH with Cl and use the -oyl chloride suffix.", "choices": null, "id": "che_0695", "kind": "concept", "lang": "en", "question": "How are acid chlorides named?", "steps": ["Start from acid name.", "Change -ic acid to -oyl.", "Add chloride: ethanoyl chloride."], "subject": "chemistry", "text": "Answer: -oyl chloride suffix.\nSteps:\n1. Start from acid name.\n2. Change -ic acid to -oyl.\n3. Add chloride: ethanoyl chloride.", "topic": "organic_naming"}
{"answer": "Polar protic solvents stabilize SN1 carbocations and leaving groups.", "choices": null, "id": "che_0696", "kind": "concept", "lang": "en", "question": "Which solvents favor SN1?", "steps": ["Carbocation needs solvation.", "Protic solvents stabilize ions.", "Examples: water, ethanol."], "subject": "chemistry", "text": "Answer: Polar protic solvents.\nSteps:\n1. Carbocation needs solvation.\n2. Protic solvents stabilize ions.\n3. Examples: water, ethanol.", "topic": "organic_mechanisms"}
{"answer": "SN1 needs ion-stabilizing polar protic solvents.", "choices": {"A": "Polar protic", "B": "Polar aprotic", "C": "Nonpolar", "D": "No solvent"}, "id": "che_0697", "kind": "multiple_choice", "lang": "en", "question": "Which solvent class speeds SN1 most?", "steps": ["Carbocation must be solvated.", "Protic polar works best.", "Select option A."], "subject": "chemistry", "text": "Answer: Polar protic.\nSteps:\n1. Carbocation must be solvated.\n2. Protic polar works best.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "The SN1 rate halves to 0.5x because rate equals k[RX].", "choices": null, "id": "che_0698", "kind": "worked_example", "lang": "en", "question": "SN1 rate = k[RX]. What happens if [RX] is halved?", "steps": ["Write: rate = k x 0.5[RX].", "Factor: 0.5 x k[RX].", "Rate becomes 0.5x."], "subject": "chemistry", "text": "Answer: Rate halves.\nSteps:\n1. Write: rate = k x 0.5[RX].\n2. Factor: 0.5 x k[RX].\n3. Rate becomes 0.5x.", "topic": "organic_mechanisms"}
{"answer": "SN1 je dvoukroková substituce přes karbokation.", "choices": null, "id": "che_0699", "kind": "concept", "lang": "cs", "question": "Co je substituce SN1?", "steps": ["Odchod skupiny.", "Vznik karbokationu.", "Atak nukleofilu."], "subject": "chemistry", "text": "Answer: Dvoukroková substituce.\nSteps:\n1. Odchod skupiny.\n2. Vznik karbokationu.\n3. Atak nukleofilu.", "topic": "organic_mechanisms"}
{"answer": "The cationic carbon is sp2 with three groups in one plane.", "choices": null, "id": "che_0700", "kind": "concept", "lang": "en", "question": "What is carbocation geometry?", "steps": ["sp2 hybridization.", "Three planar bonds.", "Empty p orbital above."], "subject": "chemistry", "text": "Answer: Trigonal planar.\nSteps:\n1. sp2 hybridization.\n2. Three planar bonds.\n3. Empty p orbital above.", "topic": "organic_mechanisms"}
{"answer": "Three planar bonds around sp2 carbon make trigonal planar geometry.", "choices": {"A": "Tetrahedral", "B": "Linear", "C": "Trigonal planar", "D": "Bent"}, "id": "che_0701", "kind": "multiple_choice", "lang": "en", "question": "What shape does a carbocation have?", "steps": ["sp2 carbon center.", "Three groups flat.", "Select option C."], "subject": "chemistry", "text": "Answer: Trigonal planar.\nSteps:\n1. sp2 carbon center.\n2. Three groups flat.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "The product is propan-2-ol, with -OH on the middle carbon.", "choices": null, "id": "che_0702", "kind": "worked_example", "lang": "en", "question": "What is the acid hydration product of propene?", "steps": ["H adds to C1.", "Water captures C2 cation.", "Product: propan-2-ol."], "subject": "chemistry", "text": "Answer: Propan-2-ol.\nSteps:\n1. H adds to C1.\n2. Water captures C2 cation.\n3. Product: propan-2-ol.", "topic": "organic_mechanisms"}
{"answer": "Primary alcohols oxidize to aldehydes then acids; secondary to ketones; tertiary resist.", "choices": null, "id": "che_0703", "kind": "concept", "lang": "en", "question": "How do alcohol classes oxidize?", "steps": ["Primary: aldehyde, then acid.", "Secondary: ketone.", "Tertiary: no reaction."], "subject": "chemistry", "text": "Answer: Class sets oxidation path.\nSteps:\n1. Primary: aldehyde, then acid.\n2. Secondary: ketone.\n3. Tertiary: no reaction.", "topic": "organic_mechanisms"}
{"answer": "Oxidace alkoholů zvyšuje oxidační číslo uhlíku: primární na kyselinu, sekundární na keton.", "choices": null, "id": "che_0704", "kind": "concept", "lang": "cs", "question": "Co je oxidace alkoholů?", "steps": ["Primární: aldehyd, kyselina.", "Sekundární: keton.", "Terciární: nereaguje."], "subject": "chemistry", "text": "Answer: Přeměna podle třídy.\nSteps:\n1. Primární: aldehyd, kyselina.\n2. Sekundární: keton.\n3. Terciární: nereaguje.", "topic": "organic_mechanisms"}
{"answer": "Primary alcohols first give aldehydes, which oxidize further to acids.", "choices": {"A": "Ketone only", "B": "Aldehyde then acid", "C": "No reaction", "D": "Alkene"}, "id": "che_0705", "kind": "multiple_choice", "lang": "en", "question": "What does primary alcohol oxidation give?", "steps": ["First aldehyde forms.", "Then acid forms.", "Select option B."], "subject": "chemistry", "text": "Answer: Aldehyde then acid.\nSteps:\n1. First aldehyde forms.\n2. Then acid forms.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "Chlorine adds across ethene to give 1,2-dichloroethane.", "choices": null, "id": "che_0706", "kind": "worked_example", "lang": "en", "question": "What is the Cl2 addition product of ethene?", "steps": ["Double bond opens.", "Each carbon takes Cl.", "Product: 1,2-dichloroethane."], "subject": "chemistry", "text": "Answer: 1,2-dichloroethane.\nSteps:\n1. Double bond opens.\n2. Each carbon takes Cl.\n3. Product: 1,2-dichloroethane.", "topic": "organic_mechanisms"}
{"answer": "Bromine water loses its brown color when an alkene is present.", "choices": null, "id": "che_0707", "kind": "concept", "lang": "en", "question": "How does the bromine test detect alkenes?", "steps": ["Brown Br2 solution added.", "Alkene consumes Br2.", "Color vanishes."], "subject": "chemistry", "text": "Answer: Brown color disappears.\nSteps:\n1. Brown Br2 solution added.\n2. Alkene consumes Br2.\n3. Color vanishes.", "topic": "organic_mechanisms"}
{"answer": "The balanced equation is C3H8 + 5O2 -> 3CO2 + 4H2O.", "choices": null, "id": "che_0708", "kind": "worked_example", "lang": "en", "question": "Balance propane combustion: C3H8 + O2 -> CO2 + H2O.", "steps": ["Balance C with 3 CO2.", "Balance H with 4 H2O.", "Balance O with 5 O2."], "subject": "chemistry", "text": "Answer: C3H8 + 5O2 -> 3CO2 + 4H2O.\nSteps:\n1. Balance C with 3 CO2.\n2. Balance H with 4 H2O.\n3. Balance O with 5 O2.", "topic": "organic_mechanisms"}
{"answer": "Alkenes consume bromine, so the brown solution decolorizes.", "choices": {"A": "Stays brown", "B": "Forms precipitate", "C": "Explodes", "D": "Decolorizes"}, "id": "che_0709", "kind": "multiple_choice", "lang": "en", "question": "What does Br2 water do with an alkene?", "steps": ["Br2 adds to C=C.", "Brown color consumed.", "Select option D."], "subject": "chemistry", "text": "Answer: Decolorizes.\nSteps:\n1. Br2 adds to C=C.\n2. Brown color consumed.\n3. Select option D.\nAnswer: (D)", "topic": "organic_mechanisms"}
{"answer": "Adicí chloru na ethen vzniká 1,2-dichlorethan.", "choices": null, "id": "che_0710", "kind": "worked_example", "lang": "cs", "question": "Jaký produkt vznikne adicí Cl2 na ethen?", "steps": ["Dvojná vazba se otevře.", "Každý uhlík přijme chlor.", "Produkt: 1,2-dichlorethan."], "subject": "chemistry", "text": "Answer: 1,2-dichlorethan.\nSteps:\n1. Dvojná vazba se otevře.\n2. Každý uhlík přijme chlor.\n3. Produkt: 1,2-dichlorethan.", "topic": "organic_mechanisms"}
{"answer": "Addition polymerization joins alkenes directly; condensation links monomers losing small molecules.", "choices": null, "id": "che_0711", "kind": "concept", "lang": "en", "question": "How do addition and condensation polymers differ?", "steps": ["Addition: C=C opens, no loss.", "Condensation: water lost.", "Examples: polyethene, nylon."], "subject": "chemistry", "text": "Answer: Direct join versus loss of water.\nSteps:\n1. Addition: C=C opens, no loss.\n2. Condensation: water lost.\n3. Examples: polyethene, nylon.", "topic": "organic_mechanisms"}
{"answer": "The PVC monomer is chloroethene, CH2=CHCl.", "choices": null, "id": "che_0712", "kind": "worked_example", "lang": "en", "question": "What monomer makes PVC?", "steps": ["PVC repeats -CH2-CHCl-.", "Monomer has C=C.", "Monomer: chloroethene."], "subject": "chemistry", "text": "Answer: Chloroethene.\nSteps:\n1. PVC repeats -CH2-CHCl-.\n2. Monomer has C=C.\n3. Monomer: chloroethene.", "topic": "organic_mechanisms"}
{"answer": "PVC polymerizes from chloroethene monomers.", "choices": {"A": "Chloroethene", "B": "Ethene", "C": "Propene", "D": "Styrene"}, "id": "che_0713", "kind": "multiple_choice", "lang": "en", "question": "Which monomer forms PVC?", "steps": ["Repeat holds Cl.", "Only chloroethene fits.", "Select option A."], "subject": "chemistry", "text": "Answer: Chloroethene.\nSteps:\n1. Repeat holds Cl.\n2. Only chloroethene fits.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "Polymerace spojuje monomery do dlouhých řetězců.", "choices": null, "id": "che_0714", "kind": "concept", "lang": "cs", "question": "Co je polymerace?", "steps": ["Monomery se spojují.", "Vzniká polymer.", "Adice nebo kondenzace."], "subject": "chemistry", "text": "Answer: Tvorba polymerů z monomerů.\nSteps:\n1. Monomery se spojují.\n2. Vzniká polymer.\n3. Adice nebo kondenzace.", "topic": "organic_mechanisms"}
{"answer": "K expressions put products over reactants with coefficients as exponents.", "choices": null, "id": "che_0715", "kind": "concept", "lang": "en", "question": "What are the rules for writing K?", "steps": ["Products in numerator.", "Reactants in denominator.", "Coefficients become exponents."], "subject": "chemistry", "text": "Answer: Products over reactants, powers.\nSteps:\n1. Products in numerator.\n2. Reactants in denominator.\n3. Coefficients become exponents.", "topic": "equilibrium"}
{"answer": "K equals [B] squared over [A] for A <-> 2B.", "choices": {"A": "[A]/[B]", "B": "[B]^2/[A]", "C": "[A]/[B]^2", "D": "[B]/[A]"}, "id": "che_0716", "kind": "multiple_choice", "lang": "en", "question": "What is K for A <-> 2B?", "steps": ["Products over reactants.", "Exponent 2 on B.", "Select option B."], "subject": "chemistry", "text": "Answer: [B]^2/[A].\nSteps:\n1. Products over reactants.\n2. Exponent 2 on B.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "K is 0.90, from 0.30 squared divided by 0.10.", "choices": null, "id": "che_0717", "kind": "worked_example", "lang": "en", "question": "For A <-> 2B with [A] = 0.10 M and [B] = 0.30 M, compute K.", "steps": ["Write: K = [B]^2/[A].", "Substitute: 0.09/0.10.", "K = 0.90."], "subject": "chemistry", "text": "Answer: 0.90.\nSteps:\n1. Write: K = [B]^2/[A].\n2. Substitute: 0.09/0.10.\n3. K = 0.90.", "topic": "equilibrium"}
{"answer": "Chemická rovnováha je stav stejných rychlostí obou směrů reakce.", "choices": null, "id": "che_0718", "kind": "concept", "lang": "cs", "question": "Co je chemická rovnováha?", "steps": ["Oba směry stejně rychlé.", "Koncentrace stálé.", "Dynamický stav."], "subject": "chemistry", "text": "Answer: Stejné rychlosti obou směrů.\nSteps:\n1. Oba směry stejně rychlé.\n2. Koncentrace stálé.\n3. Dynamický stav.", "topic": "equilibrium"}
{"answer": "With K = 10^8, products vastly outnumber reactants at equilibrium.", "choices": {"A": "Reactants dominate", "B": "Nothing reacts", "C": "Products dominate", "D": "K is invalid"}, "id": "che_0719", "kind": "multiple_choice", "lang": "en", "question": "A reaction has K = 10^8. What dominates at equilibrium?", "steps": ["Huge K favors products.", "Reactants nearly gone.", "Select option C."], "subject": "chemistry", "text": "Answer: Products dominate.\nSteps:\n1. Huge K favors products.\n2. Reactants nearly gone.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "The system shifts right because Q = 0.1 is less than K = 2.", "choices": null, "id": "che_0720", "kind": "worked_example", "lang": "en", "question": "Q = 0.1 and K = 2. Which way does the system shift?", "steps": ["Compare: 0.1 < 2.", "Too few products.", "Shifts right."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Compare: 0.1 < 2.\n2. Too few products.\n3. Shifts right.", "topic": "equilibrium"}
{"answer": "Cooling an exothermic reaction shifts it toward products.", "choices": null, "id": "che_0721", "kind": "concept", "lang": "en", "question": "How does temperature shift exothermic equilibrium?", "steps": ["Heat is a product.", "Cooling removes it.", "Shift replaces it rightward."], "subject": "chemistry", "text": "Answer: Cooling shifts right.\nSteps:\n1. Heat is a product.\n2. Cooling removes it.\n3. Shift replaces it rightward.", "topic": "equilibrium"}
{"answer": "At fixed pressure the volume grows, favoring more gas moles.", "choices": {"A": "Fewer moles", "B": "More moles", "C": "No shift", "D": "Solids"}, "id": "che_0722", "kind": "multiple_choice", "lang": "en", "question": "Adding inert gas at constant pressure shifts toward what?", "steps": ["Volume expands.", "Lower partial pressures.", "Select option B."], "subject": "chemistry", "text": "Answer: More moles.\nSteps:\n1. Volume expands.\n2. Lower partial pressures.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "High temperature shifts the exothermic Haber reaction left, cutting NH3.", "choices": null, "id": "che_0723", "kind": "worked_example", "lang": "en", "question": "How does high temperature affect NH3 yield (exothermic Haber)?", "steps": ["Heat is a product.", "Adding heat shifts left.", "NH3 yield falls."], "subject": "chemistry", "text": "Answer: Yield falls.\nSteps:\n1. Heat is a product.\n2. Adding heat shifts left.\n3. NH3 yield falls.", "topic": "equilibrium"}
{"answer": "Zahřátí endotermické rovnováhy ji posune k produktům.", "choices": null, "id": "che_0724", "kind": "worked_example", "lang": "cs", "question": "Kam posune zahřátí endotermickou rovnováhu?", "steps": ["Teplo je reaktant.", "Přidání tepla.", "Posun k produktům."], "subject": "chemistry", "text": "Answer: K produktům.\nSteps:\n1. Teplo je reaktant.\n2. Přidání tepla.\n3. Posun k produktům.", "topic": "equilibrium"}
{"answer": "Cooling an endothermic reaction lowers K as reactants gain favor.", "choices": {"A": "K rises", "B": "No change", "C": "Shifts right", "D": "K falls"}, "id": "che_0725", "kind": "multiple_choice", "lang": "en", "question": "What does cooling do to an endothermic K?", "steps": ["Heat is a reactant.", "Removing it shifts left.", "Select option D."], "subject": "chemistry", "text": "Answer: K falls.\nSteps:\n1. Heat is a reactant.\n2. Removing it shifts left.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "Coupled equilibria multiply their constants into one overall K.", "choices": null, "id": "che_0726", "kind": "concept", "lang": "en", "question": "How do coupled equilibria combine?", "steps": ["Add the equations.", "Multiply the K values.", "Intermediates cancel."], "subject": "chemistry", "text": "Answer: K values multiply.\nSteps:\n1. Add the equations.\n2. Multiply the K values.\n3. Intermediates cancel.", "topic": "equilibrium"}
{"answer": "The reverse K is 5, the reciprocal of 0.2.", "choices": null, "id": "che_0727", "kind": "worked_example", "lang": "en", "question": "Forward K = 0.20 for C <-> D. What is K for the reverse?", "steps": ["Reverse inverts the ratio.", "K_rev = 1/0.20.", "K_rev = 5."], "subject": "chemistry", "text": "Answer: 5.\nSteps:\n1. Reverse inverts the ratio.\n2. K_rev = 1/0.20.\n3. K_rev = 5.", "topic": "equilibrium"}
{"answer": "Reversing flips the ratio, so K becomes its reciprocal.", "choices": {"A": "1/K", "B": "K squared", "C": "2K", "D": "K"}, "id": "che_0728", "kind": "multiple_choice", "lang": "en", "question": "What is K of the reversed reaction?", "steps": ["Products and reactants swap.", "Ratio inverts.", "Select option A."], "subject": "chemistry", "text": "Answer: 1/K.\nSteps:\n1. Products and reactants swap.\n2. Ratio inverts.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "The solubility is 1.05 x 10^-5 M, the square root of 1.1 x 10^-10.", "choices": null, "id": "che_0729", "kind": "worked_example", "lang": "en", "question": "BaSO4 has Ksp = 1.1 x 10^-10. Compute its molar solubility.", "steps": ["Write: s^2 = Ksp.", "Substitute: s = sqrt(1.1 x 10^-10).", "s = 1.05 x 10^-5 M."], "subject": "chemistry", "text": "Answer: 1.05 x 10^-5 M.\nSteps:\n1. Write: s^2 = Ksp.\n2. Substitute: s = sqrt(1.1 x 10^-10).\n3. s = 1.05 x 10^-5 M.", "topic": "equilibrium"}
{"answer": "Nasycený roztok obsahuje maximální množství rozpuštěné látky při dané teplotě.", "choices": null, "id": "che_0730", "kind": "concept", "lang": "cs", "question": "Co je nasycený roztok?", "steps": ["Maximum rozpuštěné látky.", "Rovnováha s pevnou fází.", "Víc se nerozpustí."], "subject": "chemistry", "text": "Answer: Roztok s maximem látky.\nSteps:\n1. Maximum rozpuštěné látky.\n2. Rovnováha s pevnou fází.\n3. Víc se nerozpustí.", "topic": "equilibrium"}
{"answer": "A saturated solution holds the maximum dissolved solute at that temperature.", "choices": {"A": "No solute", "B": "Max dissolved solute", "C": "Precipitate only", "D": "Pure solvent"}, "id": "che_0731", "kind": "multiple_choice", "lang": "en", "question": "What does a saturated solution hold?", "steps": ["Dissolving at its limit.", "Solid may coexist.", "Select option B."], "subject": "chemistry", "text": "Answer: Max dissolved solute.\nSteps:\n1. Dissolving at its limit.\n2. Solid may coexist.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "A precipitate forms because Q = 5.0 x 10^-9 exceeds Ksp = 1.1 x 10^-10.", "choices": null, "id": "che_0732", "kind": "worked_example", "lang": "en", "question": "Q = 5.0e-9 for BaSO4 (Ksp = 1.1e-10). Does it precipitate?", "steps": ["Compare Q to Ksp.", "5.0e-9 > 1.1e-10.", "Yes, precipitate forms."], "subject": "chemistry", "text": "Answer: Yes, precipitates.\nSteps:\n1. Compare Q to Ksp.\n2. 5.0e-9 > 1.1e-10.\n3. Yes, precipitate forms.", "topic": "equilibrium"}
{"answer": "The electrochemical series ranks half-cells by standard reduction potential.", "choices": null, "id": "che_0733", "kind": "concept", "lang": "en", "question": "What is the electrochemical series?", "steps": ["List half-reactions.", "Order by E°.", "Top oxidizes, bottom reduces."], "subject": "chemistry", "text": "Answer: Half-cells ranked by E°.\nSteps:\n1. List half-reactions.\n2. Order by E°.\n3. Top oxidizes, bottom reduces.", "topic": "electrochemistry"}
{"answer": "The highest E° species gains electrons most eagerly.", "choices": {"A": "Lowest E°", "B": "Negative E°", "C": "Highest E°", "D": "Zero E°"}, "id": "che_0734", "kind": "multiple_choice", "lang": "en", "question": "Which species is the strongest oxidizing agent?", "steps": ["Oxidizers want electrons.", "Highest E° wants most.", "Select option C."], "subject": "chemistry", "text": "Answer: Highest E°.\nSteps:\n1. Oxidizers want electrons.\n2. Highest E° wants most.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "The cell potential is 0.78 V, from 0.34 - (-0.44).", "choices": null, "id": "che_0735", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Fe/Cu with E(Fe) = -0.44 V and E(Cu) = 0.34 V.", "steps": ["Cathode is Cu at 0.34 V.", "Anode is Fe at -0.44 V.", "E = 0.34 - (-0.44) = 0.78 V."], "subject": "chemistry", "text": "Answer: 0.78 V.\nSteps:\n1. Cathode is Cu at 0.34 V.\n2. Anode is Fe at -0.44 V.\n3. E = 0.34 - (-0.44) = 0.78 V.", "topic": "electrochemistry"}
{"answer": "Elektrochemická řada řadí kovy podle standardního potenciálu.", "choices": null, "id": "che_0736", "kind": "concept", "lang": "cs", "question": "Co je elektrochemická řada?", "steps": ["Seznam poloreakcí.", "Seřazení podle E°.", "Předpovídá reakce."], "subject": "chemistry", "text": "Answer: Žebříček potenciálů.\nSteps:\n1. Seznam poloreakcí.\n2. Seřazení podle E°.\n3. Předpovídá reakce.", "topic": "electrochemistry"}
{"answer": "Metals above hydrogen reduce H+ to H2 gas in acids.", "choices": {"A": "Dissolves in acids", "B": "Never reacts", "C": "Plates hydrogen", "D": "Explodes"}, "id": "che_0737", "kind": "multiple_choice", "lang": "en", "question": "What does a metal above H in the series do?", "steps": ["It reduces H+.", "H2 gas evolves.", "Select option A."], "subject": "chemistry", "text": "Answer: Dissolves in acids.\nSteps:\n1. It reduces H+.\n2. H2 gas evolves.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "Positive E°cell predicts a spontaneous redox reaction.", "choices": null, "id": "che_0738", "kind": "concept", "lang": "en", "question": "How does E° predict redox spontaneity?", "steps": ["Compute E°cell.", "Positive means ΔG negative.", "Reaction runs forward."], "subject": "chemistry", "text": "Answer: Positive E° means spontaneous.\nSteps:\n1. Compute E°cell.\n2. Positive means ΔG negative.\n3. Reaction runs forward.", "topic": "electrochemistry"}
{"answer": "ΔG is -114 kJ, from -2 x 96485 x 0.59 J.", "choices": null, "id": "che_0739", "kind": "worked_example", "lang": "en", "question": "Compute ΔG for n = 2 and E = 0.59 V (F = 96485 C/mol).", "steps": ["Write: ΔG = -2 x 96485 x 0.59.", "Multiply: -113,852 J.", "ΔG = -114 kJ."], "subject": "chemistry", "text": "Answer: -114 kJ.\nSteps:\n1. Write: ΔG = -2 x 96485 x 0.59.\n2. Multiply: -113,852 J.\n3. ΔG = -114 kJ.", "topic": "electrochemistry"}
{"answer": "The potential is 0.53 V, from 0.59 - 0.0296 x log(100).", "choices": null, "id": "che_0740", "kind": "worked_example", "lang": "en", "question": "E° = 0.59 V, n = 2, Q = 100 at 25 C. Compute E.", "steps": ["Write: E = 0.59 - 0.0296 x 2.", "Subtract: 0.59 - 0.0592.", "E = 0.53 V."], "subject": "chemistry", "text": "Answer: 0.53 V.\nSteps:\n1. Write: E = 0.59 - 0.0296 x 2.\n2. Subtract: 0.59 - 0.0592.\n3. E = 0.53 V.", "topic": "electrochemistry"}
{"answer": "With Q = 1, the log term vanishes and E equals E°.", "choices": {"A": "E is zero", "B": "E equals E°", "C": "E doubles", "D": "E reverses"}, "id": "che_0741", "kind": "multiple_choice", "lang": "en", "question": "What is E when Q = 1 in the Nernst equation?", "steps": ["log(1) = 0.", "Correction term zero.", "Select option B."], "subject": "chemistry", "text": "Answer: E equals E°.\nSteps:\n1. log(1) = 0.\n2. Correction term zero.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "Molten NaCl electrolysis yields sodium metal and chlorine gas.", "choices": null, "id": "che_0742", "kind": "concept", "lang": "en", "question": "What are the products of molten NaCl electrolysis?", "steps": ["Cathode: Na+ to Na.", "Anode: Cl- to Cl2.", "No water involved."], "subject": "chemistry", "text": "Answer: Na and Cl2.\nSteps:\n1. Cathode: Na+ to Na.\n2. Anode: Cl- to Cl2.\n3. No water involved.", "topic": "electrochemistry"}
{"answer": "Vzniká sodík na katodě a chlor na anodě.", "choices": null, "id": "che_0743", "kind": "worked_example", "lang": "cs", "question": "Jaké produkty dá elektrolýza taveniny NaCl?", "steps": ["Katoda: Na+ na Na.", "Anoda: Cl- na Cl2.", "Produkty: Na a Cl2."], "subject": "chemistry", "text": "Answer: Na a Cl2.\nSteps:\n1. Katoda: Na+ na Na.\n2. Anoda: Cl- na Cl2.\n3. Produkty: Na a Cl2.", "topic": "electrochemistry"}
{"answer": "The chlorine volume is 22.4 L, from 1.00 mol times 22.414 L/mol.", "choices": null, "id": "che_0744", "kind": "worked_example", "lang": "en", "question": "What volume of Cl2 at STP comes from 2.00 mol of electrons?", "steps": ["2 e- give 1 Cl2: 1.00 mol.", "Multiply: 1.00 x 22.414.", "V = 22.4 L."], "subject": "chemistry", "text": "Answer: 22.4 L.\nSteps:\n1. 2 e- give 1 Cl2: 1.00 mol.\n2. Multiply: 1.00 x 22.414.\n3. V = 22.4 L.", "topic": "electrochemistry"}
{"answer": "Sodium ions reduce to sodium metal at the cathode.", "choices": {"A": "Na metal", "B": "H2 gas", "C": "O2 gas", "D": "NaOH"}, "id": "che_0745", "kind": "multiple_choice", "lang": "en", "question": "What forms at the cathode in molten NaCl electrolysis?", "steps": ["Na+ gains electron.", "Metal deposits.", "Select option A."], "subject": "chemistry", "text": "Answer: Na metal.\nSteps:\n1. Na+ gains electron.\n2. Metal deposits.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "Lithium-ion cells shuttle Li+ between graphite and metal oxide electrodes.", "choices": null, "id": "che_0746", "kind": "concept", "lang": "en", "question": "How does a lithium-ion battery work?", "steps": ["Li+ leaves graphite.", "Li+ enters oxide.", "Reverse on charge."], "subject": "chemistry", "text": "Answer: Li+ shuttles between electrodes.\nSteps:\n1. Li+ leaves graphite.\n2. Li+ enters oxide.\n3. Reverse on charge.", "topic": "electrochemistry"}
{"answer": "The charge is 24,121 C, from 0.250 mol times 96,485 C/mol.", "choices": null, "id": "che_0747", "kind": "worked_example", "lang": "en", "question": "What charge do 0.250 mol of electrons carry?", "steps": ["Write: Q = 0.250 x 96485.", "Multiply.", "Q = 24,121 C."], "subject": "chemistry", "text": "Answer: 24,121 C.\nSteps:\n1. Write: Q = 0.250 x 96485.\n2. Multiply.\n3. Q = 24,121 C.", "topic": "electrochemistry"}
{"answer": "Lithiový akumulátor přenáší ionty Li+ mezi elektrodami.", "choices": null, "id": "che_0748", "kind": "concept", "lang": "cs", "question": "Co je lithiový akumulátor?", "steps": ["Li+ putují mezi elektrodami.", "Grafit a oxid kovu.", "Dobíjecí chemie."], "subject": "chemistry", "text": "Answer: Článek s Li+ ionty.\nSteps:\n1. Li+ putují mezi elektrodami.\n2. Grafit a oxid kovu.\n3. Dobíjecí chemie.", "topic": "electrochemistry"}
{"answer": "Lithium ions carry the charge inside a Li-ion cell.", "choices": {"A": "Electrons only", "B": "H+", "C": "Li+", "D": "O2-"}, "id": "che_0749", "kind": "multiple_choice", "lang": "en", "question": "What is the charge carrier in a Li-ion cell?", "steps": ["Ions cross electrolyte.", "Those ions are Li+.", "Select option C."], "subject": "chemistry", "text": "Answer: Li+.\nSteps:\n1. Ions cross electrolyte.\n2. Those ions are Li+.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "The plated iron mass is 3.13 g, from 10,800 C giving 0.05597 mol Fe.", "choices": null, "id": "che_0750", "kind": "worked_example", "lang": "en", "question": "What mass of Fe plates from Fe2+ at 3.00 A for 1.00 h (M = 55.845 g/mol)?", "steps": ["Q = 3.00 x 3600 = 10,800 C.", "Mol e- = 0.11193; Fe = 0.05597 mol.", "Mass = 0.05597 x 55.845 = 3.13 g."], "subject": "chemistry", "text": "Answer: 3.13 g.\nSteps:\n1. Q = 3.00 x 3600 = 10,800 C.\n2. Mol e- = 0.11193; Fe = 0.05597 mol.\n3. Mass = 0.05597 x 55.845 = 3.13 g.", "topic": "electrochemistry"}
{"answer": "The atomic mass unit is 1/12 the mass of a carbon-12 atom.", "choices": null, "id": "che_0751", "kind": "concept", "lang": "en", "question": "What is the atomic mass unit?", "steps": ["Based on carbon-12.", "One unit is 1/12 of it.", "Equals 1.661e-27 kg."], "subject": "chemistry", "text": "Answer: 1/12 of carbon-12.\nSteps:\n1. Based on carbon-12.\n2. One unit is 1/12 of it.\n3. Equals 1.661e-27 kg.", "topic": "stoichiometry"}
{"answer": "One amu is defined as 1/12 the mass of a carbon-12 atom.", "choices": {"A": "1 gram", "B": "1/12 of carbon-12", "C": "1 mole", "D": "1 liter"}, "id": "che_0752", "kind": "multiple_choice", "lang": "en", "question": "What does 1 amu equal?", "steps": ["Carbon-12 standard.", "Divide by 12.", "Select option B."], "subject": "chemistry", "text": "Answer: 1/12 of carbon-12.\nSteps:\n1. Carbon-12 standard.\n2. Divide by 12.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "The mass is 100.90 g, from 5.00 mol times 20.180 g/mol.", "choices": null, "id": "che_0753", "kind": "worked_example", "lang": "en", "question": "What mass is 5.00 mol of neon (M = 20.180 g/mol)?", "steps": ["Write: m = 5.00 x 20.180.", "Multiply.", "m = 100.90 g."], "subject": "chemistry", "text": "Answer: 100.90 g.\nSteps:\n1. Write: m = 5.00 x 20.180.\n2. Multiply.\n3. m = 100.90 g.", "topic": "stoichiometry"}
{"answer": "Atomová hmotnostní jednotka je 1/12 hmotnosti atomu uhlíku 12.", "choices": null, "id": "che_0754", "kind": "concept", "lang": "cs", "question": "Co je atomová hmotnostní jednotka?", "steps": ["Základ uhlík 12.", "Jednotka je 1/12.", "Rovná se 1,661e-27 kg."], "subject": "chemistry", "text": "Answer: 1/12 uhlíku 12.\nSteps:\n1. Základ uhlík 12.\n2. Jednotka je 1/12.\n3. Rovná se 1,661e-27 kg.", "topic": "stoichiometry"}
{"answer": "There are 0.494 mol, from 12.0 g divided by 24.305 g/mol.", "choices": null, "id": "che_0755", "kind": "worked_example", "lang": "en", "question": "How many moles are in 12.0 g of magnesium (M = 24.305 g/mol)?", "steps": ["Write: n = 12.0/24.305.", "Divide.", "n = 0.494 mol."], "subject": "chemistry", "text": "Answer: 0.494 mol.\nSteps:\n1. Write: n = 12.0/24.305.\n2. Divide.\n3. n = 0.494 mol.", "topic": "stoichiometry"}
{"answer": "Ammonia totals 17.03 g/mol from 1 N and 3 H.", "choices": {"A": "14.01 g/mol", "B": "16.04 g/mol", "C": "17.03 g/mol", "D": "18.02 g/mol"}, "id": "che_0756", "kind": "multiple_choice", "lang": "en", "question": "What is the molar mass of NH3?", "steps": ["14.01 + 3x1.008.", "Total 17.03.", "Select option C."], "subject": "chemistry", "text": "Answer: 17.03 g/mol.\nSteps:\n1. 14.01 + 3x1.008.\n2. Total 17.03.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "Mass spectrometry weighs isotopes to give average atomic masses.", "choices": null, "id": "che_0757", "kind": "concept", "lang": "en", "question": "How does mass spectrometry give atomic mass?", "steps": ["Ions sort by mass.", "Abundances measured.", "Weighted average taken."], "subject": "chemistry", "text": "Answer: Weighted isotope average.\nSteps:\n1. Ions sort by mass.\n2. Abundances measured.\n3. Weighted average taken.", "topic": "stoichiometry"}
{"answer": "There are 1.00 x 10^23 atoms, from 0.1665 mol times Avogadro's number.", "choices": null, "id": "che_0758", "kind": "worked_example", "lang": "en", "question": "How many atoms are in 2.00 g of carbon (M = 12.011 g/mol)?", "steps": ["Moles = 2.00/12.011 = 0.1665.", "Multiply: 0.1665 x 6.022 x 10^23.", "N = 1.00 x 10^23."], "subject": "chemistry", "text": "Answer: 1.00 x 10^23.\nSteps:\n1. Moles = 2.00/12.011 = 0.1665.\n2. Multiply: 0.1665 x 6.022 x 10^23.\n3. N = 1.00 x 10^23.", "topic": "stoichiometry"}
{"answer": "Hmotnost je 41,44 g, protože 0,2 krát 207,2 se rovná 41,44.", "choices": null, "id": "che_0759", "kind": "worked_example", "lang": "cs", "question": "Jaká je hmotnost 0,2 molu olova (M = 207,2 g/mol)?", "steps": ["Napiš vzorec: m = 0,2 x 207,2.", "Vynásob.", "m = 41,44 g."], "subject": "chemistry", "text": "Answer: 41,44 g.\nSteps:\n1. Napiš vzorec: m = 0,2 x 207,2.\n2. Vynásob.\n3. m = 41,44 g.", "topic": "stoichiometry"}
{"answer": "The balanced equation is H2 + Cl2 -> 2HCl.", "choices": {"A": "1, 1, 2", "B": "2, 1, 2", "C": "1, 2, 2", "D": "2, 2, 2"}, "id": "che_0760", "kind": "multiple_choice", "lang": "en", "question": "What coefficients balance H2 + Cl2 -> HCl?", "steps": ["H: 2 HCl.", "Cl: 2 HCl.", "Select option A."], "subject": "chemistry", "text": "Answer: 1, 1, 2.\nSteps:\n1. H: 2 HCl.\n2. Cl: 2 HCl.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "The CO2 mass is 33.0 g, from 0.75 mol times 44.01 g/mol.", "choices": null, "id": "che_0761", "kind": "worked_example", "lang": "en", "question": "What mass of CO2 forms from 0.25 mol of propane (C3H8 + 5O2 -> 3CO2 + 4H2O)?", "steps": ["Moles CO2 = 0.25 x 3 = 0.75.", "Multiply: 0.75 x 44.01.", "Mass = 33.0 g."], "subject": "chemistry", "text": "Answer: 33.0 g.\nSteps:\n1. Moles CO2 = 0.25 x 3 = 0.75.\n2. Multiply: 0.75 x 44.01.\n3. Mass = 33.0 g.", "topic": "stoichiometry"}
{"answer": "Atom economy is the share of reactant mass ending in the desired product.", "choices": null, "id": "che_0762", "kind": "concept", "lang": "en", "question": "What is atom economy?", "steps": ["Divide product mass by reactants.", "Times 100 percent.", "Higher means greener."], "subject": "chemistry", "text": "Answer: Product share of mass.\nSteps:\n1. Divide product mass by reactants.\n2. Times 100 percent.\n3. Higher means greener.", "topic": "stoichiometry"}
{"answer": "Full atom economy means every reactant atom lands in the product.", "choices": {"A": "No product forms", "B": "Half is waste", "C": "Gas evolves", "D": "All atoms in product"}, "id": "che_0763", "kind": "multiple_choice", "lang": "en", "question": "What does 100% atom economy mean?", "steps": ["No atoms wasted.", "All in desired product.", "Select option D."], "subject": "chemistry", "text": "Answer: All atoms in product.\nSteps:\n1. No atoms wasted.\n2. All in desired product.\n3. Select option D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "Limitující reaktant určíš porovnáním poměrů molů ke koeficientům.", "choices": null, "id": "che_0764", "kind": "concept", "lang": "cs", "question": "Jak se určí limitující reaktant?", "steps": ["Vyděl moly koeficientem.", "Nejmenší podíl limituje.", "Ten určí výtěžek."], "subject": "chemistry", "text": "Answer: Nejmenším poměrem molů.\nSteps:\n1. Vyděl moly koeficientem.\n2. Nejmenší podíl limituje.\n3. Ten určí výtěžek.", "topic": "stoichiometry"}
{"answer": "The ammonia mass is 56.3 g, from 3.307 mol times 17.031 g/mol.", "choices": null, "id": "che_0765", "kind": "worked_example", "lang": "en", "question": "What mass of NH3 forms from 10.0 g H2 with excess N2?", "steps": ["Moles H2 = 10.0/2.016 = 4.960.", "NH3 = 4.960 x 2/3 = 3.307 mol.", "Mass = 3.307 x 17.031 = 56.3 g."], "subject": "chemistry", "text": "Answer: 56.3 g.\nSteps:\n1. Moles H2 = 10.0/2.016 = 4.960.\n2. NH3 = 4.960 x 2/3 = 3.307 mol.\n3. Mass = 3.307 x 17.031 = 56.3 g.", "topic": "stoichiometry"}
{"answer": "Molality counts moles per kilogram of solvent, unlike molarity per liter of solution.", "choices": {"A": "L of solution", "B": "kg of solvent", "C": "kg of solution", "D": "L of solvent"}, "id": "che_0766", "kind": "multiple_choice", "lang": "en", "question": "How is molality defined?", "steps": ["Moles of solute.", "Per kg of solvent.", "Select option B."], "subject": "chemistry", "text": "Answer: kg of solvent.\nSteps:\n1. Moles of solute.\n2. Per kg of solvent.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "The molality is 0.500 m, from 1.00 mol divided by 2.00 kg.", "choices": null, "id": "che_0767", "kind": "worked_example", "lang": "en", "question": "1.00 mol of NaCl dissolves in 2.00 kg of water. Find molality.", "steps": ["Write: m = 1.00/2.00.", "Divide.", "m = 0.500 mol/kg."], "subject": "chemistry", "text": "Answer: 0.500 m.\nSteps:\n1. Write: m = 1.00/2.00.\n2. Divide.\n3. m = 0.500 mol/kg.", "topic": "stoichiometry"}
{"answer": "Objem je 44,8 l, protože 2 krát 22,414 se rovná 44,828.", "choices": null, "id": "che_0768", "kind": "worked_example", "lang": "cs", "question": "Jaký objem mají 2 moly plynu za normálních podmínek?", "steps": ["Napiš vzorec: V = 2 x 22,414.", "Vynásob.", "V = 44,8 l."], "subject": "chemistry", "text": "Answer: 44,8 l.\nSteps:\n1. Napiš vzorec: V = 2 x 22,414.\n2. Vynásob.\n3. V = 44,8 l.", "topic": "stoichiometry"}
{"answer": "The volume is 11.2 L, from 0.500 mol times 22.414 L/mol.", "choices": {"A": "11.2 L", "B": "22.4 L", "C": "5.6 L", "D": "44.8 L"}, "id": "che_0769", "kind": "multiple_choice", "lang": "en", "question": "What volume does 0.500 mol of gas occupy at STP?", "steps": ["Multiply: 0.500 x 22.414.", "Result 11.2 L.", "Select option A."], "subject": "chemistry", "text": "Answer: 11.2 L.\nSteps:\n1. Multiply: 0.500 x 22.414.\n2. Result 11.2 L.\n3. Select option A.\nAnswer: (A)", "topic": "stoichiometry"}
{"answer": "The hydronium ion H3O+ is a proton bound to a water molecule.", "choices": null, "id": "che_0770", "kind": "concept", "lang": "en", "question": "What is the hydronium ion?", "steps": ["H+ joins H2O.", "Forms H3O+.", "True form of acidity."], "subject": "chemistry", "text": "Answer: H+ bound to water.\nSteps:\n1. H+ joins H2O.\n2. Forms H3O+.\n3. True form of acidity.", "topic": "acids_bases"}
{"answer": "Free protons hydrate instantly to H3O+ in water.", "choices": {"A": "Bare H+", "B": "H2 gas", "C": "H3O+", "D": "OH-"}, "id": "che_0771", "kind": "multiple_choice", "lang": "en", "question": "How does H+ exist in water?", "steps": ["Protons hydrate.", "Form is H3O+.", "Select option C."], "subject": "chemistry", "text": "Answer: H3O+.\nSteps:\n1. Protons hydrate.\n2. Form is H3O+.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "The pH is 2.10, from -log(0.0080).", "choices": null, "id": "che_0772", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.0080 M HCl.", "steps": ["[H+] = 0.0080 M.", "pH = -log(0.0080).", "pH = 2.10."], "subject": "chemistry", "text": "Answer: 2.10.\nSteps:\n1. [H+] = 0.0080 M.\n2. pH = -log(0.0080).\n3. pH = 2.10.", "topic": "acids_bases"}
{"answer": "Hydroniový ion H3O+ je proton navázaný na molekulu vody.", "choices": null, "id": "che_0773", "kind": "concept", "lang": "cs", "question": "Co je hydroniový ion?", "steps": ["H+ se váže na H2O.", "Vzniká H3O+.", "Skutečná forma kyselosti."], "subject": "chemistry", "text": "Answer: H+ navázaný na vodu.\nSteps:\n1. H+ se váže na H2O.\n2. Vzniká H3O+.\n3. Skutečná forma kyselosti.", "topic": "acids_bases"}
{"answer": "Removing a proton from H3O+ leaves water, H2O.", "choices": {"A": "OH(-)", "B": "H2O", "C": "O2(-)", "D": "H2"}, "id": "che_0774", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate base of H3O+?", "steps": ["Remove one H+.", "Left with H2O.", "Select option B."], "subject": "chemistry", "text": "Answer: H2O.\nSteps:\n1. Remove one H+.\n2. Left with H2O.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "Hydroxide concentration is 1.0 x 10^-11 M, from pOH = 14 - 3 = 11.", "choices": null, "id": "che_0775", "kind": "worked_example", "lang": "en", "question": "A solution has pH 3.00. Compute [OH-].", "steps": ["pOH = 14 - 3.00 = 11.00.", "Write: [OH-] = 10^(-11).", "[OH-] = 1.0 x 10^-11 M."], "subject": "chemistry", "text": "Answer: 1.0 x 10^-11 M.\nSteps:\n1. pOH = 14 - 3.00 = 11.00.\n2. Write: [OH-] = 10^(-11).\n3. [OH-] = 1.0 x 10^-11 M.", "topic": "acids_bases"}
{"answer": "A strong acid has a weak conjugate base, and vice versa.", "choices": null, "id": "che_0776", "kind": "concept", "lang": "en", "question": "How are acid and conjugate base strengths related?", "steps": ["Strong acid donates easily.", "Its base holds H+ weakly.", "Ka x Kb = Kw proves it."], "subject": "chemistry", "text": "Answer: Inversely related strengths.\nSteps:\n1. Strong acid donates easily.\n2. Its base holds H+ weakly.\n3. Ka x Kb = Kw proves it.", "topic": "acids_bases"}
{"answer": "Kb is 5.6 x 10^-10, from 1.0 x 10^-14 divided by 1.8 x 10^-5.", "choices": null, "id": "che_0777", "kind": "worked_example", "lang": "en", "question": "An acid has Ka = 1.8 x 10^-5. Compute Kb of its conjugate base.", "steps": ["Write: Kb = Kw/Ka.", "Substitute: 1.0e-14/1.8e-5.", "Kb = 5.6 x 10^-10."], "subject": "chemistry", "text": "Answer: 5.6 x 10^-10.\nSteps:\n1. Write: Kb = Kw/Ka.\n2. Substitute: 1.0e-14/1.8e-5.\n3. Kb = 5.6 x 10^-10.", "topic": "acids_bases"}
{"answer": "The product Ka x Kb always equals Kw = 1.0 x 10^-14.", "choices": {"A": "1.0 x 10^-14", "B": "14", "C": "1.0", "D": "0"}, "id": "che_0778", "kind": "multiple_choice", "lang": "en", "question": "What is Ka x Kb for NH4+/NH3 at 25 C?", "steps": ["Conjugate pair rule.", "Product equals Kw.", "Select option A."], "subject": "chemistry", "text": "Answer: 1.0 x 10^-14.\nSteps:\n1. Conjugate pair rule.\n2. Product equals Kw.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "pH je 2,40, protože -log(0,004) = 2,40.", "choices": null, "id": "che_0779", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,004 M HCl.", "steps": ["HCl disociuje plně.", "pH = -log(0,004).", "pH = 2,40."], "subject": "chemistry", "text": "Answer: 2,40.\nSteps:\n1. HCl disociuje plně.\n2. pH = -log(0,004).\n3. pH = 2,40.", "topic": "acids_bases"}
{"answer": "Salt ions from weak acids or bases react with water to shift pH.", "choices": null, "id": "che_0780", "kind": "concept", "lang": "en", "question": "Why do some salts change pH?", "steps": ["Weak-parent ions hydrolyze.", "H+ or OH- released.", "Strong-parent ions stay neutral."], "subject": "chemistry", "text": "Answer: Hydrolysis of weak-parent ions.\nSteps:\n1. Weak-parent ions hydrolyze.\n2. H+ or OH- released.\n3. Strong-parent ions stay neutral.", "topic": "acids_bases"}
{"answer": "Both ions come from strong parents, so neither hydrolyzes.", "choices": {"A": "Acidic", "B": "Neutral", "C": "Basic", "D": "Cannot tell"}, "id": "che_0781", "kind": "multiple_choice", "lang": "en", "question": "Is NaCl solution acidic or basic?", "steps": ["Na+ from strong base.", "Cl- from strong acid.", "Select option B."], "subject": "chemistry", "text": "Answer: Neutral.\nSteps:\n1. Na+ from strong base.\n2. Cl- from strong acid.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "The buffer pH is 3.76, from 4.76 + log(0.1).", "choices": null, "id": "che_0782", "kind": "worked_example", "lang": "en", "question": "An acetate buffer (pKa = 4.76) has base/acid = 0.10. Find pH.", "steps": ["Write: pH = 4.76 + log(0.10).", "log(0.10) = -1.", "pH = 3.76."], "subject": "chemistry", "text": "Answer: 3.76.\nSteps:\n1. Write: pH = 4.76 + log(0.10).\n2. log(0.10) = -1.\n3. pH = 3.76.", "topic": "acids_bases"}
{"answer": "Buffers are made by mixing a weak acid with its conjugate salt.", "choices": null, "id": "che_0783", "kind": "concept", "lang": "en", "question": "How are buffers prepared?", "steps": ["Pick acid near target pH.", "Add its salt.", "Ratio sets exact pH."], "subject": "chemistry", "text": "Answer: Weak acid plus its salt.\nSteps:\n1. Pick acid near target pH.\n2. Add its salt.\n3. Ratio sets exact pH.", "topic": "acids_bases"}
{"answer": "Hydrolýza solí je reakce iontů soli s vodou měnící pH.", "choices": null, "id": "che_0784", "kind": "concept", "lang": "cs", "question": "Co je hydrolýza solí?", "steps": ["Ionty reagují s vodou.", "Vzniká H+ nebo OH-.", "Silné páry nereagují."], "subject": "chemistry", "text": "Answer: Reakce iontů s vodou.\nSteps:\n1. Ionty reagují s vodou.\n2. Vzniká H+ nebo OH-.\n3. Silné páry nereagují.", "topic": "acids_bases"}
{"answer": "The conjugate base hydrolyzes, leaving excess OH- above pH 7.", "choices": {"A": "pH 7", "B": "Below 7", "C": "Above 7", "D": "pH 1"}, "id": "che_0785", "kind": "multiple_choice", "lang": "en", "question": "What is the equivalence pH of weak acid with strong base?", "steps": ["Salt of weak acid forms.", "Anion makes OH-.", "Select option C."], "subject": "chemistry", "text": "Answer: Above 7.\nSteps:\n1. Salt of weak acid forms.\n2. Anion makes OH-.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "There are 10.0 mmol, from 25.0 mL times 0.400 M.", "choices": null, "id": "che_0786", "kind": "worked_example", "lang": "en", "question": "How many millimoles are in 25.0 mL of 0.400 M NaOH?", "steps": ["Write: mmol = 25.0 x 0.400.", "Multiply.", "mmol = 10.0."], "subject": "chemistry", "text": "Answer: 10.0 mmol.\nSteps:\n1. Write: mmol = 25.0 x 0.400.\n2. Multiply.\n3. mmol = 10.0.", "topic": "acids_bases"}
{"answer": "[OH-] je 1 x 10^-2 M, protože pOH = 14 - 12 = 2.", "choices": null, "id": "che_0787", "kind": "worked_example", "lang": "cs", "question": "Roztok má pH 12. Vypočítej [OH-].", "steps": ["pOH = 14 - 12 = 2.", "Napiš vzorec: [OH-] = 10^(-2).", "[OH-] = 1 x 10^-2 M."], "subject": "chemistry", "text": "Answer: 1 x 10^-2 M.\nSteps:\n1. pOH = 14 - 12 = 2.\n2. Napiš vzorec: [OH-] = 10^(-2).\n3. [OH-] = 1 x 10^-2 M.", "topic": "acids_bases"}
{"answer": "Cyanide hydrolyzes to make OH-, so the solution is basic.", "choices": {"A": "Basic", "B": "Acidic", "C": "Neutral", "D": "Cannot tell"}, "id": "che_0788", "kind": "multiple_choice", "lang": "en", "question": "Is KCN solution acidic or basic?", "steps": ["CN- from weak HCN.", "It makes OH-.", "Select option A."], "subject": "chemistry", "text": "Answer: Basic.\nSteps:\n1. CN- from weak HCN.\n2. It makes OH-.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "Hydrogen is +1 except in metal hydrides, where it is -1.", "choices": null, "id": "che_0789", "kind": "concept", "lang": "en", "question": "When is hydrogen's oxidation state negative?", "steps": ["Normal rule: H is +1.", "Metals less electronegative.", "In hydrides H is -1."], "subject": "chemistry", "text": "Answer: In metal hydrides.\nSteps:\n1. Normal rule: H is +1.\n2. Metals less electronegative.\n3. In hydrides H is -1.", "topic": "redox"}
{"answer": "Calcium is +2, so each H must be -1 to balance.", "choices": {"A": "+1", "B": "-1", "C": "0", "D": "+2"}, "id": "che_0790", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of H in CaH2?", "steps": ["Ca is +2.", "Solve: 2 + 2H = 0.", "H = -1; select B."], "subject": "chemistry", "text": "Answer: -1.\nSteps:\n1. Ca is +2.\n2. Solve: 2 + 2H = 0.\n3. H = -1; select B.\nAnswer: (B)", "topic": "redox"}
{"answer": "Boron is +3, since 3(+1) + B + 3(-2) = 0.", "choices": null, "id": "che_0791", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of B in H3BO3.", "steps": ["Assign H +1 and O -2.", "Equation: 3 + B - 6 = 0.", "B = +3."], "subject": "chemistry", "text": "Answer: +3.\nSteps:\n1. Assign H +1 and O -2.\n2. Equation: 3 + B - 6 = 0.\n3. B = +3.", "topic": "redox"}
{"answer": "Redukční činidlo odevzdává elektrony a samo se oxiduje.", "choices": null, "id": "che_0792", "kind": "concept", "lang": "cs", "question": "Co je redukční činidlo?", "steps": ["Odevzdává elektrony.", "Samo se oxiduje.", "Příklad: Zn, H2."], "subject": "chemistry", "text": "Answer: Dárce elektronů.\nSteps:\n1. Odevzdává elektrony.\n2. Samo se oxiduje.\n3. Příklad: Zn, H2.", "topic": "redox"}
{"answer": "Magnesium loses electrons to oxygen, so it is the reducing agent.", "choices": {"A": "Mg", "B": "O2", "C": "MgO", "D": "Heat"}, "id": "che_0793", "kind": "multiple_choice", "lang": "en", "question": "In 2Mg + O2 -> 2MgO, what is the reducing agent?", "steps": ["Mg is oxidized.", "Oxidized species reduces.", "Select option A."], "subject": "chemistry", "text": "Answer: Mg.\nSteps:\n1. Mg is oxidized.\n2. Oxidized species reduces.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "The balanced equation is C + 2H2 -> CH4.", "choices": null, "id": "che_0794", "kind": "worked_example", "lang": "en", "question": "Balance: C + H2 -> CH4.", "steps": ["Balance H with 2 H2.", "Check C: 1 each side.", "Result: C + 2H2 -> CH4."], "subject": "chemistry", "text": "Answer: C + 2H2 -> CH4.\nSteps:\n1. Balance H with 2 H2.\n2. Check C: 1 each side.\n3. Result: C + 2H2 -> CH4.", "topic": "redox"}
{"answer": "Balance first as in acid, then neutralize H+ with OH- into water.", "choices": null, "id": "che_0795", "kind": "concept", "lang": "en", "question": "How is redox balanced in basic solution?", "steps": ["Balance as in acid.", "Add OH- to both sides.", "Combine H+ and OH- to H2O."], "subject": "chemistry", "text": "Answer: Acid method plus OH- fix.\nSteps:\n1. Balance as in acid.\n2. Add OH- to both sides.\n3. Combine H+ and OH- to H2O.", "topic": "redox"}
{"answer": "Three electrons are gained as nitrogen drops from +5 to +2.", "choices": null, "id": "che_0796", "kind": "worked_example", "lang": "en", "question": "How many electrons are gained in NO3- -> NO?", "steps": ["N goes +5 to +2.", "Change = 3 down.", "Electrons gained = 3."], "subject": "chemistry", "text": "Answer: 3 electrons.\nSteps:\n1. N goes +5 to +2.\n2. Change = 3 down.\n3. Electrons gained = 3.", "topic": "redox"}
{"answer": "Chlorine gains electrons to form chloride, so Cl2 is reduced.", "choices": {"A": "Na", "B": "NaCl", "C": "Cl2", "D": "None"}, "id": "che_0797", "kind": "multiple_choice", "lang": "en", "question": "In 2Na + Cl2 -> 2NaCl, what is reduced?", "steps": ["Cl goes 0 to -1.", "That is reduction.", "Select option C."], "subject": "chemistry", "text": "Answer: Cl2.\nSteps:\n1. Cl goes 0 to -1.\n2. That is reduction.\n3. Select option C.\nAnswer: (C)", "topic": "redox"}
{"answer": "Uhlík má oxidační číslo +2, protože C + (-2) = 0.", "choices": null, "id": "che_0798", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo uhlíku v CO.", "steps": ["Přiřaď O -2.", "Rovnice: C - 2 = 0.", "C = +2."], "subject": "chemistry", "text": "Answer: +2.\nSteps:\n1. Přiřaď O -2.\n2. Rovnice: C - 2 = 0.\n3. C = +2.", "topic": "redox"}
{"answer": "Smelting reduces metal oxides with carbon or CO to free metals.", "choices": null, "id": "che_0799", "kind": "concept", "lang": "en", "question": "How does smelting extract metals?", "steps": ["Heat oxide ore.", "Carbon reduces it.", "Metal melts out."], "subject": "chemistry", "text": "Answer: Carbon reduces ore oxides.\nSteps:\n1. Heat oxide ore.\n2. Carbon reduces it.\n3. Metal melts out.", "topic": "redox"}
{"answer": "Coke provides CO that reduces iron ore in the blast furnace.", "choices": {"A": "Oxygen", "B": "Coke", "C": "Water", "D": "Acid"}, "id": "che_0800", "kind": "multiple_choice", "lang": "en", "question": "What reduces iron ore in a blast furnace?", "steps": ["Need a reducer.", "Coke supplies CO.", "Select option B."], "subject": "chemistry", "text": "Answer: Coke.\nSteps:\n1. Need a reducer.\n2. Coke supplies CO.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "The balanced equation is TiCl4 + 2Mg -> Ti + 2MgCl2.", "choices": null, "id": "che_0801", "kind": "worked_example", "lang": "en", "question": "Balance: TiCl4 + Mg -> Ti + MgCl2.", "steps": ["Balance Cl with 2 MgCl2.", "Balance Mg with 2 Mg.", "Result: TiCl4 + 2Mg -> Ti + 2MgCl2."], "subject": "chemistry", "text": "Answer: TiCl4 + 2Mg -> Ti + 2MgCl2.\nSteps:\n1. Balance Cl with 2 MgCl2.\n2. Balance Mg with 2 Mg.\n3. Result: TiCl4 + 2Mg -> Ti + 2MgCl2.", "topic": "redox"}
{"answer": "V metalurgii se oxidace používá k pražení a redukce k získání kovu.", "choices": null, "id": "che_0802", "kind": "concept", "lang": "cs", "question": "Jak se redox používá v metalurgii?", "steps": ["Pražení: oxidace sulfidů.", "Tavení: redukce oxidů.", "Výsledek: čistý kov."], "subject": "chemistry", "text": "Answer: Pražení a redukce rud.\nSteps:\n1. Pražení: oxidace sulfidů.\n2. Tavení: redukce oxidů.\n3. Výsledek: čistý kov.", "topic": "redox"}
{"answer": "Phosphorus is +5, since 2P + 5(-2) = 0 gives P = +5.", "choices": {"A": "+2", "B": "+3", "C": "+4", "D": "+5"}, "id": "che_0803", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of P in P2O5?", "steps": ["Assign O -2.", "Solve: 2P - 10 = 0.", "P = +5; select D."], "subject": "chemistry", "text": "Answer: +5.\nSteps:\n1. Assign O -2.\n2. Solve: 2P - 10 = 0.\n3. P = +5; select D.\nAnswer: (D)", "topic": "redox"}
{"answer": "Redox indicators change color at a specific electrode potential.", "choices": null, "id": "che_0804", "kind": "concept", "lang": "en", "question": "What are redox indicators?", "steps": ["Oxidized form one color.", "Reduced form another.", "Flip marks endpoint."], "subject": "chemistry", "text": "Answer: Color at set potential.\nSteps:\n1. Oxidized form one color.\n2. Reduced form another.\n3. Flip marks endpoint.", "topic": "redox"}
{"answer": "Vyčíslená rovnice je 2Ag2O -> 4Ag + O2.", "choices": null, "id": "che_0805", "kind": "worked_example", "lang": "cs", "question": "Vyčísli: Ag2O -> Ag + O2.", "steps": ["Kyslík: 2 Ag2O a 1 O2.", "Stříbro: 4 Ag.", "Výsledek: 2Ag2O -> 4Ag + O2."], "subject": "chemistry", "text": "Answer: 2Ag2O -> 4Ag + O2.\nSteps:\n1. Kyslík: 2 Ag2O a 1 O2.\n2. Stříbro: 4 Ag.\n3. Výsledek: 2Ag2O -> 4Ag + O2.", "topic": "redox"}
{"answer": "The Mn2+ ion has manganese at +2 by its charge.", "choices": {"A": "+2", "B": "+4", "C": "+7", "D": "0"}, "id": "che_0806", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of Mn in Mn2+?", "steps": ["Monoatomic ion rule.", "State equals charge.", "Select option A."], "subject": "chemistry", "text": "Answer: +2.\nSteps:\n1. Monoatomic ion rule.\n2. State equals charge.\n3. Select option A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Two electrons are lost as copper goes from 0 to +2.", "choices": null, "id": "che_0807", "kind": "worked_example", "lang": "en", "question": "How many electrons are lost in Cu -> Cu2+?", "steps": ["Change: 0 to +2.", "Difference = 2 up.", "Electrons lost = 2."], "subject": "chemistry", "text": "Answer: 2 electrons.\nSteps:\n1. Change: 0 to +2.\n2. Difference = 2 up.\n3. Electrons lost = 2.", "topic": "redox"}
{"answer": "Heat is energy in transit while temperature measures average particle energy.", "choices": null, "id": "che_0808", "kind": "concept", "lang": "en", "question": "How do heat and temperature differ?", "steps": ["Heat flows between bodies.", "Temperature is intensity.", "Same T can hold more heat."], "subject": "chemistry", "text": "Answer: Energy flow versus intensity.\nSteps:\n1. Heat flows between bodies.\n2. Temperature is intensity.\n3. Same T can hold more heat.", "topic": "thermochemistry"}
{"answer": "Temperature reflects the average kinetic energy of particles.", "choices": {"A": "Total mass", "B": "Total volume", "C": "Average kinetic energy", "D": "Total charge"}, "id": "che_0809", "kind": "multiple_choice", "lang": "en", "question": "What does temperature measure?", "steps": ["Faster particles mean hotter.", "Average kinetic energy.", "Select option C."], "subject": "chemistry", "text": "Answer: Average kinetic energy.\nSteps:\n1. Faster particles mean hotter.\n2. Average kinetic energy.\n3. Select option C.\nAnswer: (C)", "topic": "thermochemistry"}
{"answer": "The internal energy change is -150 J, from -100 plus -50 J.", "choices": null, "id": "che_0810", "kind": "worked_example", "lang": "en", "question": "A system releases 100 J of heat and does 50 J of work. Find ΔU.", "steps": ["Write: ΔU = -100 + (-50).", "Add.", "ΔU = -150 J."], "subject": "chemistry", "text": "Answer: -150 J.\nSteps:\n1. Write: ΔU = -100 + (-50).\n2. Add.\n3. ΔU = -150 J.", "topic": "thermochemistry"}
{"answer": "Teplota je míra průměrné kinetické energie částic.", "choices": null, "id": "che_0811", "kind": "concept", "lang": "cs", "question": "Co je teplota?", "steps": ["Průměrná energie částic.", "Měří se teploměrem.", "Jednotky: °C, K."], "subject": "chemistry", "text": "Answer: Míra energie částic.\nSteps:\n1. Průměrná energie částic.\n2. Měří se teploměrem.\n3. Jednotky: °C, K.", "topic": "thermochemistry"}
{"answer": "The SI unit of heat energy is the joule.", "choices": {"A": "Joule", "B": "Watt", "C": "Newton", "D": "Pascal"}, "id": "che_0812", "kind": "multiple_choice", "lang": "en", "question": "What is the SI unit of heat?", "steps": ["Heat is energy.", "Energy unit is joule.", "Select option A."], "subject": "chemistry", "text": "Answer: Joule.\nSteps:\n1. Heat is energy.\n2. Energy unit is joule.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "The heat is 20.9 kJ, from 1000 g x 4.184 x 5.", "choices": null, "id": "che_0813", "kind": "worked_example", "lang": "en", "question": "How much heat warms 1.00 kg of water by 5.00 C?", "steps": ["Write: q = 1000 x 4.184 x 5.", "Multiply: 20,920 J.", "q = 20.9 kJ."], "subject": "chemistry", "text": "Answer: 20.9 kJ.\nSteps:\n1. Write: q = 1000 x 4.184 x 5.\n2. Multiply: 20,920 J.\n3. q = 20.9 kJ.", "topic": "thermochemistry"}
{"answer": "Metals heat quickly because their specific heats are low.", "choices": null, "id": "che_0814", "kind": "concept", "lang": "en", "question": "Why do metals heat faster than water?", "steps": ["Low specific heat.", "Little energy per degree.", "Example: Al 0.897 J/gC."], "subject": "chemistry", "text": "Answer: Low specific heat.\nSteps:\n1. Low specific heat.\n2. Little energy per degree.\n3. Example: Al 0.897 J/gC.", "topic": "thermochemistry"}
{"answer": "The rise is 26.0 C, from 2000 J divided by (200 x 0.385).", "choices": null, "id": "che_0815", "kind": "worked_example", "lang": "en", "question": "200 g of Cu (c = 0.385 J/gC) gains 2000 J. Find ΔT.", "steps": ["Write: ΔT = 2000/(200 x 0.385).", "Divide: 2000/77.", "ΔT = 26.0 C."], "subject": "chemistry", "text": "Answer: 26.0 C.\nSteps:\n1. Write: ΔT = 2000/(200 x 0.385).\n2. Divide: 2000/77.\n3. ΔT = 26.0 C.", "topic": "thermochemistry"}
{"answer": "Water's hydrogen bonding gives it the highest common specific heat.", "choices": {"A": "Iron", "B": "Water", "C": "Copper", "D": "Lead"}, "id": "che_0816", "kind": "multiple_choice", "lang": "en", "question": "Which has the highest specific heat?", "steps": ["Water is 4.184 J/gC.", "Metals far lower.", "Select option B."], "subject": "chemistry", "text": "Answer: Water.\nSteps:\n1. Water is 4.184 J/gC.\n2. Metals far lower.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "Potřebné teplo je 4184 J, protože 1000 x 4,184 x 1 se rovná 4184.", "choices": null, "id": "che_0817", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla ohřeje 1 kg vody o 1 °C?", "steps": ["Napiš vzorec: q = 1000 x 4,184 x 1.", "Vynásob.", "q = 4184 J."], "subject": "chemistry", "text": "Answer: 4184 J.\nSteps:\n1. Napiš vzorec: q = 1000 x 4,184 x 1.\n2. Vynásob.\n3. q = 4184 J.", "topic": "thermochemistry"}
{"answer": "Latent heat changes phase at constant temperature without a thermometer rise.", "choices": null, "id": "che_0818", "kind": "concept", "lang": "en", "question": "What is latent heat?", "steps": ["Heat for phase change.", "Temperature stays flat.", "Bonds rearrange instead."], "subject": "chemistry", "text": "Answer: Heat of phase change.\nSteps:\n1. Heat for phase change.\n2. Temperature stays flat.\n3. Bonds rearrange instead.", "topic": "thermochemistry"}
{"answer": "Phase changes absorb or release heat while temperature holds steady.", "choices": {"A": "Rising T", "B": "Falling T", "C": "Any T", "D": "Constant T"}, "id": "che_0819", "kind": "multiple_choice", "lang": "en", "question": "At what temperature does latent heat act?", "steps": ["Phase change plateau.", "T stays fixed.", "Select option D."], "subject": "chemistry", "text": "Answer: Constant T.\nSteps:\n1. Phase change plateau.\n2. T stays fixed.\n3. Select option D.\nAnswer: (D)", "topic": "thermochemistry"}
{"answer": "The overall ΔH is +50 kJ, from +20 plus +30 kJ.", "choices": null, "id": "che_0820", "kind": "worked_example", "lang": "en", "question": "A->B has ΔH = +20 kJ and B->C has ΔH = +30 kJ. Find ΔH for A->C.", "steps": ["Apply Hess's law: sum steps.", "Add: 20 + 30.", "ΔH = +50 kJ."], "subject": "chemistry", "text": "Answer: +50 kJ.\nSteps:\n1. Apply Hess's law: sum steps.\n2. Add: 20 + 30.\n3. ΔH = +50 kJ.", "topic": "thermochemistry"}
{"answer": "Skupenské teplo je teplo potřebné ke změně skupenství při stálé teplotě.", "choices": null, "id": "che_0821", "kind": "concept", "lang": "cs", "question": "Co je skupenské teplo?", "steps": ["Teplo fázové změny.", "Teplota se nemění.", "Příklady: tání, var."], "subject": "chemistry", "text": "Answer: Teplo změny skupenství.\nSteps:\n1. Teplo fázové změny.\n2. Teplota se nemění.\n3. Příklady: tání, var.", "topic": "thermochemistry"}
{"answer": "Sublimation absorbs heat to free molecules directly into gas.", "choices": {"A": "Endothermic", "B": "Exothermic", "C": "Athermal", "D": "Nuclear"}, "id": "che_0822", "kind": "multiple_choice", "lang": "en", "question": "Is sublimation endothermic or exothermic?", "steps": ["Bonds break to gas.", "Breaking needs energy.", "Select option A."], "subject": "chemistry", "text": "Answer: Endothermic.\nSteps:\n1. Bonds break to gas.\n2. Breaking needs energy.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "ΔG is -90 kJ, from -60 minus 300 x 0.100.", "choices": null, "id": "che_0823", "kind": "worked_example", "lang": "en", "question": "ΔH = -60 kJ and ΔS = +0.100 kJ/K at 300 K. Compute ΔG.", "steps": ["Write: ΔG = -60 - 300 x 0.100.", "Simplify: -60 - 30.", "ΔG = -90 kJ."], "subject": "chemistry", "text": "Answer: -90 kJ.\nSteps:\n1. Write: ΔG = -60 - 300 x 0.100.\n2. Simplify: -60 - 30.\n3. ΔG = -90 kJ.", "topic": "thermochemistry"}
{"answer": "Samovolný děj probíhá bez vnějšího přísunu energie.", "choices": null, "id": "che_0824", "kind": "concept", "lang": "cs", "question": "Co je samovolný děj?", "steps": ["Běží sám od sebe.", "ΔG je záporné.", "Může být pomalý."], "subject": "chemistry", "text": "Answer: Děj bez vnější energie.\nSteps:\n1. Běží sám od sebe.\n2. ΔG je záporné.\n3. Může být pomalý.", "topic": "thermochemistry"}
{"answer": "Positive ΔG means the process needs driving and is nonspontaneous.", "choices": {"A": "Spontaneous", "B": "Nonspontaneous", "C": "At equilibrium", "D": "Impossible"}, "id": "che_0825", "kind": "multiple_choice", "lang": "en", "question": "What does ΔG > 0 mean?", "steps": ["Free energy rises.", "Needs external drive.", "Select option B."], "subject": "chemistry", "text": "Answer: Nonspontaneous.\nSteps:\n1. Free energy rises.\n2. Needs external drive.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "Vaporizing needs 77.2 kJ, from 2.00 mol times 38.6 kJ/mol.", "choices": null, "id": "che_0826", "kind": "worked_example", "lang": "en", "question": "How much heat vaporizes 2.00 mol of ethanol (ΔHvap = 38.6 kJ/mol)?", "steps": ["Write: q = 2.00 x 38.6.", "Multiply.", "q = 77.2 kJ."], "subject": "chemistry", "text": "Answer: 77.2 kJ.\nSteps:\n1. Write: q = 2.00 x 38.6.\n2. Multiply.\n3. q = 77.2 kJ.", "topic": "thermochemistry"}
{"answer": "Substituents are listed alphabetically, ignoring di- and tri- prefixes.", "choices": null, "id": "che_0827", "kind": "concept", "lang": "en", "question": "In what order are substituents listed?", "steps": ["Sort alphabetically.", "Ignore di-, tri-.", "Example: ethyl before methyl."], "subject": "chemistry", "text": "Answer: Alphabetical order.\nSteps:\n1. Sort alphabetically.\n2. Ignore di-, tri-.\n3. Example: ethyl before methyl.", "topic": "organic_naming"}
{"answer": "Ethyl comes before methyl alphabetically.", "choices": {"A": "Methyl", "B": "Ethyl", "C": "Propyl", "D": "Butyl"}, "id": "che_0828", "kind": "multiple_choice", "lang": "en", "question": "Which substituent is listed first?", "steps": ["Compare first letters.", "E beats M.", "Select option B."], "subject": "chemistry", "text": "Answer: Ethyl.\nSteps:\n1. Compare first letters.\n2. E beats M.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is 2-methylbutane: four carbons with a methyl on carbon 2.", "choices": null, "id": "che_0829", "kind": "worked_example", "lang": "en", "question": "Name CH3CH(CH3)CH2CH3.", "steps": ["Longest chain: 4 = butane.", "Methyl on carbon 2.", "Name: 2-methylbutane."], "subject": "chemistry", "text": "Answer: 2-methylbutane.\nSteps:\n1. Longest chain: 4 = butane.\n2. Methyl on carbon 2.\n3. Name: 2-methylbutane.", "topic": "organic_naming"}
{"answer": "Substituenty se řadí abecedně bez ohledu na předpony di- a tri-.", "choices": null, "id": "che_0830", "kind": "concept", "lang": "cs", "question": "Jak se řadí substituenty?", "steps": ["Abecední pořadí.", "Di- a tri- se ignorují.", "Příklad: ethyl před methyl."], "subject": "chemistry", "text": "Answer: Abecedně.\nSteps:\n1. Abecední pořadí.\n2. Di- a tri- se ignorují.\n3. Příklad: ethyl před methyl.", "topic": "organic_naming"}
{"answer": "The di- prefix counts two identical substituents.", "choices": {"A": "Two methyls", "B": "Two chains", "C": "Two bonds", "D": "Two rings"}, "id": "che_0831", "kind": "multiple_choice", "lang": "en", "question": "What does dimethyl mean?", "steps": ["Di- means two.", "Two methyl groups.", "Select option A."], "subject": "chemistry", "text": "Answer: Two methyls.\nSteps:\n1. Di- means two.\n2. Two methyl groups.\n3. Select option A.\nAnswer: (A)", "topic": "organic_naming"}
{"answer": "The name is 2-methylpentane: five carbons with a methyl on carbon 2.", "choices": null, "id": "che_0832", "kind": "worked_example", "lang": "en", "question": "Name (CH3)2CHCH2CH2CH3.", "steps": ["Longest chain: 5 = pentane.", "Methyl on carbon 2.", "Name: 2-methylpentane."], "subject": "chemistry", "text": "Answer: 2-methylpentane.\nSteps:\n1. Longest chain: 5 = pentane.\n2. Methyl on carbon 2.\n3. Name: 2-methylpentane.", "topic": "organic_naming"}
{"answer": "The parent chain is the longest one, preferring most substituents on ties.", "choices": null, "id": "che_0833", "kind": "concept", "lang": "en", "question": "How is the parent chain chosen?", "steps": ["Find longest chain.", "Tie-break: most branches.", "It sets the root name."], "subject": "chemistry", "text": "Answer: Longest with most branches.\nSteps:\n1. Find longest chain.\n2. Tie-break: most branches.\n3. It sets the root name.", "topic": "organic_naming"}
{"answer": "The name is chloroethene: chlorine on a two-carbon double bond.", "choices": null, "id": "che_0834", "kind": "worked_example", "lang": "en", "question": "Name CH2=CHCl.", "steps": ["Count 2 carbons, double bond.", "Chlorine substituent.", "Name: chloroethene."], "subject": "chemistry", "text": "Answer: Chloroethene.\nSteps:\n1. Count 2 carbons, double bond.\n2. Chlorine substituent.\n3. Name: chloroethene.", "topic": "organic_naming"}
{"answer": "Chloroethene is commonly called vinyl chloride.", "choices": {"A": "Ethylene", "B": "Acetylene", "C": "Vinyl chloride", "D": "Styrene"}, "id": "che_0835", "kind": "multiple_choice", "lang": "en", "question": "What is the common name of CH2=CHCl?", "steps": ["Vinyl group plus chloride.", "Standard trivial name.", "Select option C."], "subject": "chemistry", "text": "Answer: Vinyl chloride.\nSteps:\n1. Vinyl group plus chloride.\n2. Standard trivial name.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "C3H8 je propan.", "choices": null, "id": "che_0836", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu C3H8.", "steps": ["Tři uhlíky.", "Jen jednoduché vazby.", "Název: propan."], "subject": "chemistry", "text": "Answer: Propan.\nSteps:\n1. Tři uhlíky.\n2. Jen jednoduché vazby.\n3. Název: propan.", "topic": "organic_naming"}
{"answer": "Dienes have two double bonds and use the -diene suffix with locants.", "choices": null, "id": "che_0837", "kind": "concept", "lang": "en", "question": "How are dienes named?", "steps": ["Find both double bonds.", "Number lowest set.", "Suffix -diene with locants."], "subject": "chemistry", "text": "Answer: Locants plus -diene.\nSteps:\n1. Find both double bonds.\n2. Number lowest set.\n3. Suffix -diene with locants.", "topic": "organic_naming"}
{"answer": "Two double bonds use the -diene suffix.", "choices": {"A": "-ene", "B": "-diene", "C": "-yne", "D": "-ane"}, "id": "che_0838", "kind": "multiple_choice", "lang": "en", "question": "What suffix marks two double bonds?", "steps": ["One gives -ene.", "Two give -diene.", "Select option B."], "subject": "chemistry", "text": "Answer: -diene.\nSteps:\n1. One gives -ene.\n2. Two give -diene.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is buta-1,3-diene: double bonds at carbons 1 and 3.", "choices": null, "id": "che_0839", "kind": "worked_example", "lang": "en", "question": "Name CH2=CHCH=CH2.", "steps": ["Count 4 carbons.", "Bonds at 1 and 3.", "Name: buta-1,3-diene."], "subject": "chemistry", "text": "Answer: Buta-1,3-diene.\nSteps:\n1. Count 4 carbons.\n2. Bonds at 1 and 3.\n3. Name: buta-1,3-diene.", "topic": "organic_naming"}
{"answer": "Phenyl attaches the ring directly while benzyl adds a CH2 spacer.", "choices": null, "id": "che_0840", "kind": "concept", "lang": "en", "question": "How do phenyl and benzyl differ?", "steps": ["Phenyl is C6H5-.", "Benzyl is C6H5CH2-.", "Spacer changes reactivity."], "subject": "chemistry", "text": "Answer: Direct versus CH2 spacer.\nSteps:\n1. Phenyl is C6H5-.\n2. Benzyl is C6H5CH2-.\n3. Spacer changes reactivity.", "topic": "organic_naming"}
{"answer": "Benzyl je skupina C6H5CH2- s methylenovým můstkem.", "choices": null, "id": "che_0841", "kind": "concept", "lang": "cs", "question": "Co je benzyl?", "steps": ["Fenyl plus CH2.", "Vzorec C6H5CH2-.", "Příklad: benzylchlorid."], "subject": "chemistry", "text": "Answer: Skupina C6H5CH2-.\nSteps:\n1. Fenyl plus CH2.\n2. Vzorec C6H5CH2-.\n3. Příklad: benzylchlorid.", "topic": "organic_naming"}
{"answer": "The C6H5CH2- fragment is called benzyl.", "choices": {"A": "Phenyl", "B": "Benzyl", "C": "Tolyl", "D": "Styryl"}, "id": "che_0842", "kind": "multiple_choice", "lang": "en", "question": "What is the C6H5CH2- group called?", "steps": ["Ring plus CH2 spacer.", "Named benzyl.", "Select option B."], "subject": "chemistry", "text": "Answer: Benzyl.\nSteps:\n1. Ring plus CH2 spacer.\n2. Named benzyl.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "The name is pentanoic acid: five carbons ending in -COOH.", "choices": null, "id": "che_0843", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2CH2CH2COOH.", "steps": ["Count 5 carbons.", "-COOH gives -oic acid.", "Name: pentanoic acid."], "subject": "chemistry", "text": "Answer: Pentanoic acid.\nSteps:\n1. Count 5 carbons.\n2. -COOH gives -oic acid.\n3. Name: pentanoic acid.", "topic": "organic_naming"}
{"answer": "CH4 je methan.", "choices": null, "id": "che_0844", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu CH4.", "steps": ["Jeden uhlík.", "Jen jednoduché vazby.", "Název: methan."], "subject": "chemistry", "text": "Answer: Methan.\nSteps:\n1. Jeden uhlík.\n2. Jen jednoduché vazby.\n3. Název: methan.", "topic": "organic_naming"}
{"answer": "Esterification joins a carboxylic acid and an alcohol, releasing water.", "choices": null, "id": "che_0845", "kind": "concept", "lang": "en", "question": "How do esters form?", "steps": ["Acid plus alcohol.", "Water splits out.", "Acid catalyst helps."], "subject": "chemistry", "text": "Answer: Acid plus alcohol minus water.\nSteps:\n1. Acid plus alcohol.\n2. Water splits out.\n3. Acid catalyst helps.", "topic": "organic_naming"}
{"answer": "Planar carbocations are attacked from both faces, giving a racemic mix.", "choices": null, "id": "che_0846", "kind": "concept", "lang": "en", "question": "Why does SN1 give racemic products?", "steps": ["Carbocation is flat.", "Attack from either face.", "Both enantiomers form."], "subject": "chemistry", "text": "Answer: Flat ion, both faces.\nSteps:\n1. Carbocation is flat.\n2. Attack from either face.\n3. Both enantiomers form.", "topic": "organic_mechanisms"}
{"answer": "SN1 attack from both faces yields a racemic mixture.", "choices": {"A": "Inversion", "B": "Racemic", "C": "Retention", "D": "None"}, "id": "che_0847", "kind": "multiple_choice", "lang": "en", "question": "What stereochemistry results from SN1?", "steps": ["Planar intermediate.", "Both faces attacked.", "Select option B."], "subject": "chemistry", "text": "Answer: Racemic.\nSteps:\n1. Planar intermediate.\n2. Both faces attacked.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "The SN2 rate stays the same because 2 x 0.5 equals 1.", "choices": null, "id": "che_0848", "kind": "worked_example", "lang": "en", "question": "SN2 rate = k[RX][Nu]. [RX] doubles and [Nu] halves. What happens?", "steps": ["Write: rate = k x 2[RX] x 0.5[Nu].", "Factor: 1 x k[RX][Nu].", "Rate unchanged."], "subject": "chemistry", "text": "Answer: Unchanged.\nSteps:\n1. Write: rate = k x 2[RX] x 0.5[Nu].\n2. Factor: 1 x k[RX][Nu].\n3. Rate unchanged.", "topic": "organic_mechanisms"}
{"answer": "Racemizace je vznik směsi obou enantiomerů 1:1.", "choices": null, "id": "che_0849", "kind": "concept", "lang": "cs", "question": "Co je racemizace?", "steps": ["Planární meziprodukt.", "Atak z obou stran.", "Směs 1:1 bez otáčivosti."], "subject": "chemistry", "text": "Answer: Směs enantiomerů 1:1.\nSteps:\n1. Planární meziprodukt.\n2. Atak z obou stran.\n3. Směs 1:1 bez otáčivosti.", "topic": "organic_mechanisms"}
{"answer": "E1 first loses the leaving group, then a base removes a proton.", "choices": null, "id": "che_0850", "kind": "concept", "lang": "en", "question": "What are the E1 mechanism steps?", "steps": ["Leaving group departs.", "Carbocation forms.", "Base removes H+."], "subject": "chemistry", "text": "Answer: Ionize, then deprotonate.\nSteps:\n1. Leaving group departs.\n2. Carbocation forms.\n3. Base removes H+.", "topic": "organic_mechanisms"}
{"answer": "The E1 intermediate is a carbocation formed after leaving group loss.", "choices": {"A": "Carbocation", "B": "Carbanion", "C": "Radical", "D": "Epoxide"}, "id": "che_0851", "kind": "multiple_choice", "lang": "en", "question": "What intermediate forms in E1?", "steps": ["Leaving group leaves first.", "Positive carbon remains.", "Select option A."], "subject": "chemistry", "text": "Answer: Carbocation.\nSteps:\n1. Leaving group leaves first.\n2. Positive carbon remains.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "HI adds across ethene to give iodoethane.", "choices": null, "id": "che_0852", "kind": "worked_example", "lang": "en", "question": "What is the HI addition product of ethene?", "steps": ["H adds to one carbon.", "I adds to the other.", "Product: iodoethane."], "subject": "chemistry", "text": "Answer: Iodoethane.\nSteps:\n1. H adds to one carbon.\n2. I adds to the other.\n3. Product: iodoethane.", "topic": "organic_mechanisms"}
{"answer": "Bromine adds to opposite faces of the double bond via a bromonium ion.", "choices": null, "id": "che_0853", "kind": "concept", "lang": "en", "question": "Why is Br2 addition anti?", "steps": ["Bromonium ion forms.", "Backside attack opens it.", "Groups land opposite."], "subject": "chemistry", "text": "Answer: Bromonium forces backside attack.\nSteps:\n1. Bromonium ion forms.\n2. Backside attack opens it.\n3. Groups land opposite.", "topic": "organic_mechanisms"}
{"answer": "Anti-adice přidává skupiny na opačné strany dvojné vazby.", "choices": null, "id": "che_0854", "kind": "concept", "lang": "cs", "question": "Co je anti-adice?", "steps": ["Skupiny na opačné strany.", "Přes bromoniový ion.", "Opak syn-adice."], "subject": "chemistry", "text": "Answer: Adice na opačné strany.\nSteps:\n1. Skupiny na opačné strany.\n2. Přes bromoniový ion.\n3. Opak syn-adice.", "topic": "organic_mechanisms"}
{"answer": "Bromine adds anti across the double bond.", "choices": {"A": "Syn", "B": "Random", "C": "Anti", "D": "No addition"}, "id": "che_0855", "kind": "multiple_choice", "lang": "en", "question": "How does Br2 add to alkenes?", "steps": ["Bromonium intermediate.", "Backside opening.", "Select option C."], "subject": "chemistry", "text": "Answer: Anti.\nSteps:\n1. Bromonium intermediate.\n2. Backside opening.\n3. Select option C.\nAnswer: (C)", "topic": "organic_mechanisms"}
{"answer": "Full hydrogenation of propyne gives propane.", "choices": null, "id": "che_0856", "kind": "worked_example", "lang": "en", "question": "What is the product of propyne + excess H2 (Pt)?", "steps": ["Triple bond saturates fully.", "Each carbon gains 2 H.", "Product: propane."], "subject": "chemistry", "text": "Answer: Propane.\nSteps:\n1. Triple bond saturates fully.\n2. Each carbon gains 2 H.\n3. Product: propane.", "topic": "organic_mechanisms"}
{"answer": "Both hydrogens add from the catalyst surface to the same face.", "choices": null, "id": "che_0857", "kind": "concept", "lang": "en", "question": "Why is catalytic hydrogenation syn?", "steps": ["Alkene adsorbs on metal.", "H atoms add together.", "Same face results."], "subject": "chemistry", "text": "Answer: Same-face surface addition.\nSteps:\n1. Alkene adsorbs on metal.\n2. H atoms add together.\n3. Same face results.", "topic": "organic_mechanisms"}
{"answer": "The product is 2-methylpropan-2-ol, via the tertiary carbocation.", "choices": null, "id": "che_0858", "kind": "worked_example", "lang": "en", "question": "What is the acid hydration product of 2-methylpropene?", "steps": ["H adds to CH2 end.", "Tertiary cation forms.", "Water captures it: 2-methylpropan-2-ol."], "subject": "chemistry", "text": "Answer: 2-methylpropan-2-ol.\nSteps:\n1. H adds to CH2 end.\n2. Tertiary cation forms.\n3. Water captures it: 2-methylpropan-2-ol.", "topic": "organic_mechanisms"}
{"answer": "Hydration places -OH on the more substituted carbon per Markovnikov.", "choices": {"A": "Markovnikov", "B": "Anti-Markovnikov", "C": "Random", "D": "Zaitsev"}, "id": "che_0859", "kind": "multiple_choice", "lang": "en", "question": "Which rule governs acid hydration?", "steps": ["Stable cation forms.", "OH lands on it.", "Select option A."], "subject": "chemistry", "text": "Answer: Markovnikov.\nSteps:\n1. Stable cation forms.\n2. OH lands on it.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "Úplnou hydrogenací ethynu vzniká ethan.", "choices": null, "id": "che_0860", "kind": "worked_example", "lang": "cs", "question": "Jaký produkt vznikne hydrogenací ethynu s nadbytkem H2?", "steps": ["Trojná vazba se nasytí.", "Každý uhlík získá 2 H.", "Produkt: ethan."], "subject": "chemistry", "text": "Answer: Ethan.\nSteps:\n1. Trojná vazba se nasytí.\n2. Každý uhlík získá 2 H.\n3. Produkt: ethan.", "topic": "organic_mechanisms"}
{"answer": "Condensation polymers link monomers while expelling water or HCl.", "choices": null, "id": "che_0861", "kind": "concept", "lang": "en", "question": "What is condensation polymerization?", "steps": ["Bifunctional monomers join.", "Small molecule leaves.", "Examples: nylon, polyester."], "subject": "chemistry", "text": "Answer: Joining with small loss.\nSteps:\n1. Bifunctional monomers join.\n2. Small molecule leaves.\n3. Examples: nylon, polyester.", "topic": "organic_mechanisms"}
{"answer": "Nylon forms from a diamine plus a diacid with water loss.", "choices": null, "id": "che_0862", "kind": "worked_example", "lang": "en", "question": "What monomers make nylon?", "steps": ["Need two functional ends each.", "Diamine plus diacid.", "Water splits out per link."], "subject": "chemistry", "text": "Answer: Diamine plus diacid.\nSteps:\n1. Need two functional ends each.\n2. Diamine plus diacid.\n3. Water splits out per link.", "topic": "organic_mechanisms"}
{"answer": "Each nylon link expels one water molecule.", "choices": {"A": "HCl", "B": "Water", "C": "H2", "D": "CO2"}, "id": "che_0863", "kind": "multiple_choice", "lang": "en", "question": "What small molecule does nylon formation release?", "steps": ["Amide bond forms.", "H and OH leave.", "Select option B."], "subject": "chemistry", "text": "Answer: Water.\nSteps:\n1. Amide bond forms.\n2. H and OH leave.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "Kondenzační polymer vzniká spojováním monomerů za odštěpení malé molekuly.", "choices": null, "id": "che_0864", "kind": "concept", "lang": "cs", "question": "Co je kondenzační polymer?", "steps": ["Monomery se spojují.", "Odchází voda či HCl.", "Příklad: nylon."], "subject": "chemistry", "text": "Answer: Polymer se ztrátou molekuly.\nSteps:\n1. Monomery se spojují.\n2. Odchází voda či HCl.\n3. Příklad: nylon.", "topic": "organic_mechanisms"}
{"answer": "The same equilibrium state results whether starting from reactants or products.", "choices": null, "id": "che_0865", "kind": "concept", "lang": "en", "question": "Can equilibrium be reached from either side?", "steps": ["Forward reaction proceeds.", "Reverse also proceeds.", "Both meet at same state."], "subject": "chemistry", "text": "Answer: Yes, both sides meet.\nSteps:\n1. Forward reaction proceeds.\n2. Reverse also proceeds.\n3. Both meet at same state.", "topic": "equilibrium"}
{"answer": "Starting materials on either side converge to the same equilibrium.", "choices": {"A": "Reactants only", "B": "Products only", "C": "Either side", "D": "Never"}, "id": "che_0866", "kind": "multiple_choice", "lang": "en", "question": "From which side can equilibrium be reached?", "steps": ["Both directions run.", "Same state results.", "Select option C."], "subject": "chemistry", "text": "Answer: Either side.\nSteps:\n1. Both directions run.\n2. Same state results.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "K is 8.0, from 1.0 squared divided by 0.5 cubed.", "choices": null, "id": "che_0867", "kind": "worked_example", "lang": "en", "question": "For 3A <-> 2B with [A] = 0.50 M and [B] = 1.00 M, compute K.", "steps": ["Write: K = [B]^2/[A]^3.", "Substitute: 1.00/0.125.", "K = 8.0."], "subject": "chemistry", "text": "Answer: 8.0.\nSteps:\n1. Write: K = [B]^2/[A]^3.\n2. Substitute: 1.00/0.125.\n3. K = 8.0.", "topic": "equilibrium"}
{"answer": "Kc se vypočítá dosazením rovnovážných koncentrací do poměru produkty/reaktanty.", "choices": null, "id": "che_0868", "kind": "concept", "lang": "cs", "question": "Jak se vypočítá Kc z koncentrací?", "steps": ["Zjisti rovnovážné koncentrace.", "Dosaď do vzorce.", "Koeficienty jako exponenty."], "subject": "chemistry", "text": "Answer: Dosazením do poměru.\nSteps:\n1. Zjisti rovnovážné koncentrace.\n2. Dosaď do vzorce.\n3. Koeficienty jako exponenty.", "topic": "equilibrium"}
{"answer": "Kc units depend on the reaction and are often omitted.", "choices": {"A": "Always M", "B": "Always atm", "C": "Always mol", "D": "Varies or omitted"}, "id": "che_0869", "kind": "multiple_choice", "lang": "en", "question": "What are the units of Kc?", "steps": ["Depend on stoichiometry.", "Often left out.", "Select option D."], "subject": "chemistry", "text": "Answer: Varies or omitted.\nSteps:\n1. Depend on stoichiometry.\n2. Often left out.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "The system is at equilibrium with no shift.", "choices": null, "id": "che_0870", "kind": "worked_example", "lang": "en", "question": "Q = 1.0 and K = 1.0. Which way does the system shift?", "steps": ["Compare: Q equals K.", "No excess either side.", "No shift."], "subject": "chemistry", "text": "Answer: No shift.\nSteps:\n1. Compare: Q equals K.\n2. No excess either side.\n3. No shift.", "topic": "equilibrium"}
{"answer": "Pressure shifts gas equilibrium toward the side with fewer moles.", "choices": null, "id": "che_0871", "kind": "concept", "lang": "en", "question": "How does pressure shift gas equilibrium?", "steps": ["Count gas moles each side.", "High P favors fewer.", "Low P favors more."], "subject": "chemistry", "text": "Answer: Toward fewer moles at high P.\nSteps:\n1. Count gas moles each side.\n2. High P favors fewer.\n3. Low P favors more.", "topic": "equilibrium"}
{"answer": "Higher pressure favors the single product mole over two reactant moles.", "choices": {"A": "Right", "B": "Left", "C": "None", "D": "Stops"}, "id": "che_0872", "kind": "multiple_choice", "lang": "en", "question": "A(g) + B(g) <-> C(g) under pressure shifts where?", "steps": ["Two moles left, one right.", "Pressure favors fewer.", "Select option A."], "subject": "chemistry", "text": "Answer: Right.\nSteps:\n1. Two moles left, one right.\n2. Pressure favors fewer.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "Heating drives the endothermic decomposition right, toward CaO and CO2.", "choices": null, "id": "che_0873", "kind": "worked_example", "lang": "en", "question": "How does heating affect CaCO3(s) <-> CaO(s) + CO2(g)?", "steps": ["Decomposition needs heat.", "Adding heat shifts right.", "More CO2 forms."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Decomposition needs heat.\n2. Adding heat shifts right.\n3. More CO2 forms.", "topic": "equilibrium"}
{"answer": "Zahřátí posune rozklad doprava, k CaO a CO2.", "choices": null, "id": "che_0874", "kind": "worked_example", "lang": "cs", "question": "Kam posune zahřátí rozklad CaCO3?", "steps": ["Rozklad potřebuje teplo.", "Přidání tepla.", "Posun doprava."], "subject": "chemistry", "text": "Answer: Doprava.\nSteps:\n1. Rozklad potřebuje teplo.\n2. Přidání tepla.\n3. Posun doprava.", "topic": "equilibrium"}
{"answer": "Breaking CaCO3 apart requires heat input.", "choices": {"A": "Exothermic", "B": "Endothermic", "C": "Athermal", "D": "Nuclear"}, "id": "che_0875", "kind": "multiple_choice", "lang": "en", "question": "Is CaCO3 decomposition endo- or exothermic?", "steps": ["Needs furnace heat.", "Heat absorbed.", "Select option B."], "subject": "chemistry", "text": "Answer: Endothermic.\nSteps:\n1. Needs furnace heat.\n2. Heat absorbed.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "A shared ion pushes dissolution back, lowering solubility.", "choices": null, "id": "che_0876", "kind": "concept", "lang": "en", "question": "How does a common ion affect solubility?", "steps": ["Extra ion added.", "Equilibrium shifts left.", "Less solid dissolves."], "subject": "chemistry", "text": "Answer: Lowers solubility.\nSteps:\n1. Extra ion added.\n2. Equilibrium shifts left.\n3. Less solid dissolves.", "topic": "equilibrium"}
{"answer": "Added chloride suppresses AgCl dissolving, so solubility drops.", "choices": null, "id": "che_0877", "kind": "worked_example", "lang": "en", "question": "What happens to AgCl solubility in NaCl solution?", "steps": ["Cl- is the common ion.", "Dissolution shifts back.", "Solubility falls."], "subject": "chemistry", "text": "Answer: Solubility drops.\nSteps:\n1. Cl- is the common ion.\n2. Dissolution shifts back.\n3. Solubility falls.", "topic": "equilibrium"}
{"answer": "Common ions push dissolution equilibrium back toward the solid.", "choices": {"A": "Decreases it", "B": "Increases it", "C": "No effect", "D": "Dissolves all"}, "id": "che_0878", "kind": "multiple_choice", "lang": "en", "question": "What does a common ion do to solubility?", "steps": ["Shared ion added.", "Shift goes left.", "Select option A."], "subject": "chemistry", "text": "Answer: Decreases it.\nSteps:\n1. Shared ion added.\n2. Shift goes left.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "Selective precipitation separates ions by their different Ksp values.", "choices": null, "id": "che_0879", "kind": "concept", "lang": "en", "question": "What is selective precipitation?", "steps": ["Add reagent slowly.", "Lowest Ksp falls first.", "Ions separate in order."], "subject": "chemistry", "text": "Answer: Separation by Ksp order.\nSteps:\n1. Add reagent slowly.\n2. Lowest Ksp falls first.\n3. Ions separate in order.", "topic": "equilibrium"}
{"answer": "Selektivní srážení odděluje ionty podle rozdílných součinů rozpustnosti.", "choices": null, "id": "che_0880", "kind": "concept", "lang": "cs", "question": "Co je selektivní srážení?", "steps": ["Postupné přidávání činidla.", "Nejdřív nejmenší Ksp.", "Ionty se oddělí."], "subject": "chemistry", "text": "Answer: Oddělení podle Ksp.\nSteps:\n1. Postupné přidávání činidla.\n2. Nejdřív nejmenší Ksp.\n3. Ionty se oddělí.", "topic": "equilibrium"}
{"answer": "The least soluble salt hits its Ksp first and falls out.", "choices": {"A": "Higher Ksp", "B": "Higher Q", "C": "Lower Ksp", "D": "Larger ion"}, "id": "che_0881", "kind": "multiple_choice", "lang": "en", "question": "Which salt precipitates first?", "steps": ["Compare Ksp values.", "Lowest saturates first.", "Select option C."], "subject": "chemistry", "text": "Answer: Lower Ksp.\nSteps:\n1. Compare Ksp values.\n2. Lowest saturates first.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "The solubility is 2.14 x 10^-4 M, from (3.9 x 10^-11 / 4)^(1/3).", "choices": null, "id": "che_0882", "kind": "worked_example", "lang": "en", "question": "CaF2 has Ksp = 3.9 x 10^-11. Compute its molar solubility.", "steps": ["Write: Ksp = 4s^3.", "s^3 = 3.9 x 10^-11 / 4 = 9.75 x 10^-12.", "s = 2.14 x 10^-4 M."], "subject": "chemistry", "text": "Answer: 2.14 x 10^-4 M.\nSteps:\n1. Write: Ksp = 4s^3.\n2. s^3 = 3.9 x 10^-11 / 4 = 9.75 x 10^-12.\n3. s = 2.14 x 10^-4 M.", "topic": "equilibrium"}
{"answer": "Reduction tables list E° values to compare oxidizing strength.", "choices": null, "id": "che_0883", "kind": "concept", "lang": "en", "question": "How is a standard reduction table read?", "steps": ["Higher E° on top.", "Top species oxidize.", "Bottom species reduce."], "subject": "chemistry", "text": "Answer: Top oxidizes, bottom reduces.\nSteps:\n1. Higher E° on top.\n2. Top species oxidize.\n3. Bottom species reduce.", "topic": "electrochemistry"}
{"answer": "The galvanic cathode is positive as it draws electrons in.", "choices": {"A": "Negative", "B": "Positive", "C": "Neutral", "D": "Variable"}, "id": "che_0884", "kind": "multiple_choice", "lang": "en", "question": "What is the cathode's sign in a galvanic cell?", "steps": ["Cathode accepts electrons.", "It stays positive.", "Select option B."], "subject": "chemistry", "text": "Answer: Positive.\nSteps:\n1. Cathode accepts electrons.\n2. It stays positive.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "The cell potential is 2.00 V, from 0.34 - (-1.66).", "choices": null, "id": "che_0885", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Al/Cu with E(Al) = -1.66 V and E(Cu) = 0.34 V.", "steps": ["Cathode is Cu at 0.34 V.", "Anode is Al at -1.66 V.", "E = 0.34 - (-1.66) = 2.00 V."], "subject": "chemistry", "text": "Answer: 2.00 V.\nSteps:\n1. Cathode is Cu at 0.34 V.\n2. Anode is Al at -1.66 V.\n3. E = 0.34 - (-1.66) = 2.00 V.", "topic": "electrochemistry"}
{"answer": "Standardní vodíková elektroda je referenční poločlánek s potenciálem 0,00 V.", "choices": null, "id": "che_0886", "kind": "concept", "lang": "cs", "question": "Co je standardní vodíková elektroda?", "steps": ["Vodík na platině.", "1 M H+ a 1 atm.", "Definována 0,00 V."], "subject": "chemistry", "text": "Answer: Referenční elektroda 0,00 V.\nSteps:\n1. Vodík na platině.\n2. 1 M H+ a 1 atm.\n3. Definována 0,00 V.", "topic": "electrochemistry"}
{"answer": "The hydrogen reference is defined as exactly 0.00 V.", "choices": {"A": "0.00 V", "B": "1.00 V", "C": "-1.00 V", "D": "0.34 V"}, "id": "che_0887", "kind": "multiple_choice", "lang": "en", "question": "What is the SHE potential?", "steps": ["Reference defined zero.", "All others relative.", "Select option A."], "subject": "chemistry", "text": "Answer: 0.00 V.\nSteps:\n1. Reference defined zero.\n2. All others relative.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "A cell can do electrical work equal to -nFE.", "choices": null, "id": "che_0888", "kind": "concept", "lang": "en", "question": "How does cell potential relate to work?", "steps": ["Charge times voltage.", "Work = -nFE.", "Spontaneous cells do work."], "subject": "chemistry", "text": "Answer: Work equals -nFE.\nSteps:\n1. Charge times voltage.\n2. Work = -nFE.\n3. Spontaneous cells do work.", "topic": "electrochemistry"}
{"answer": "ΔG is -386 kJ, from -2 x 96485 x 2.00 J.", "choices": null, "id": "che_0889", "kind": "worked_example", "lang": "en", "question": "Compute ΔG for n = 2 and E = 2.00 V (F = 96485 C/mol).", "steps": ["Write: ΔG = -2 x 96485 x 2.00.", "Multiply: -385,940 J.", "ΔG = -386 kJ."], "subject": "chemistry", "text": "Answer: -386 kJ.\nSteps:\n1. Write: ΔG = -2 x 96485 x 2.00.\n2. Multiply: -385,940 J.\n3. ΔG = -386 kJ.", "topic": "electrochemistry"}
{"answer": "The potential is 0.69 V, from 0.78 - 0.0296 x log(1000).", "choices": null, "id": "che_0890", "kind": "worked_example", "lang": "en", "question": "E° = 0.78 V, n = 2, Q = 1000 at 25 C. Compute E.", "steps": ["Write: E = 0.78 - 0.0296 x 3.", "Subtract: 0.78 - 0.0888.", "E = 0.69 V."], "subject": "chemistry", "text": "Answer: 0.69 V.\nSteps:\n1. Write: E = 0.78 - 0.0296 x 3.\n2. Subtract: 0.78 - 0.0888.\n3. E = 0.69 V.", "topic": "electrochemistry"}
{"answer": "The base-10 log of 1000 is 3.", "choices": {"A": "2", "B": "4", "C": "3", "D": "10"}, "id": "che_0891", "kind": "multiple_choice", "lang": "en", "question": "What is log(1000)?", "steps": ["1000 = 10^3.", "Log gives exponent.", "Select option C."], "subject": "chemistry", "text": "Answer: 3.\nSteps:\n1. 1000 = 10^3.\n2. Log gives exponent.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "Brine electrolysis gives hydrogen, chlorine, and sodium hydroxide.", "choices": null, "id": "che_0892", "kind": "concept", "lang": "en", "question": "What are the products of aqueous NaCl electrolysis?", "steps": ["Cathode: water to H2.", "Anode: Cl- to Cl2.", "NaOH builds up."], "subject": "chemistry", "text": "Answer: H2, Cl2, NaOH.\nSteps:\n1. Cathode: water to H2.\n2. Anode: Cl- to Cl2.\n3. NaOH builds up.", "topic": "electrochemistry"}
{"answer": "Vzniká vodík, chlor a hydroxid sodný.", "choices": null, "id": "che_0893", "kind": "worked_example", "lang": "cs", "question": "Jaké produkty dá elektrolýza roztoku NaCl?", "steps": ["Katoda: H2 z vody.", "Anoda: Cl2.", "Zbývá NaOH."], "subject": "chemistry", "text": "Answer: H2, Cl2, NaOH.\nSteps:\n1. Katoda: H2 z vody.\n2. Anoda: Cl2.\n3. Zbývá NaOH.", "topic": "electrochemistry"}
{"answer": "The NaOH mass is 40.00 g, from 1.00 mol times 40.00 g/mol.", "choices": null, "id": "che_0894", "kind": "worked_example", "lang": "en", "question": "What mass of NaOH forms from 1.00 mol of electrons in brine electrolysis?", "steps": ["1 e- gives 1 NaOH: 1.00 mol.", "Multiply: 1.00 x 40.00.", "Mass = 40.00 g."], "subject": "chemistry", "text": "Answer: 40.00 g.\nSteps:\n1. 1 e- gives 1 NaOH: 1.00 mol.\n2. Multiply: 1.00 x 40.00.\n3. Mass = 40.00 g.", "topic": "electrochemistry"}
{"answer": "Water reduces to hydrogen gas at the cathode.", "choices": {"A": "Na", "B": "H2", "C": "Cl2", "D": "O2"}, "id": "che_0895", "kind": "multiple_choice", "lang": "en", "question": "What forms at the cathode in aqueous NaCl electrolysis?", "steps": ["Water reduces easier than Na+.", "Product is H2.", "Select option B."], "subject": "chemistry", "text": "Answer: H2.\nSteps:\n1. Water reduces easier than Na+.\n2. Product is H2.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "The alkaline cell pairs zinc with manganese dioxide in KOH paste.", "choices": null, "id": "che_0896", "kind": "concept", "lang": "en", "question": "How does an alkaline battery work?", "steps": ["Zn anode oxidizes.", "MnO2 cathode reduces.", "KOH paste conducts."], "subject": "chemistry", "text": "Answer: Zn/MnO2 in KOH.\nSteps:\n1. Zn anode oxidizes.\n2. MnO2 cathode reduces.\n3. KOH paste conducts.", "topic": "electrochemistry"}
{"answer": "The time is 2.68 h, from 96,485 C divided by 10.0 A.", "choices": null, "id": "che_0897", "kind": "worked_example", "lang": "en", "question": "How long at 10.0 A to pass 1.00 mol of electrons?", "steps": ["Q = 1.00 x 96485 = 96,485 C.", "t = 96,485/10.0 = 9,649 s.", "t = 2.68 h."], "subject": "chemistry", "text": "Answer: 2.68 h.\nSteps:\n1. Q = 1.00 x 96485 = 96,485 C.\n2. t = 96,485/10.0 = 9,649 s.\n3. t = 2.68 h.", "topic": "electrochemistry"}
{"answer": "Suchý článek je galvanický článek s pastovým elektrolytem.", "choices": null, "id": "che_0898", "kind": "concept", "lang": "cs", "question": "Co je suchý článek?", "steps": ["Zinková nádobka.", "Uhlíková tyčinka.", "Pastový elektrolyt."], "subject": "chemistry", "text": "Answer: Článek s pastou.\nSteps:\n1. Zinková nádobka.\n2. Uhlíková tyčinka.\n3. Pastový elektrolyt.", "topic": "electrochemistry"}
{"answer": "A standard dry cell delivers about 1.5 V.", "choices": {"A": "12 V", "B": "6 V", "C": "3.7 V", "D": "1.5 V"}, "id": "che_0899", "kind": "multiple_choice", "lang": "en", "question": "What voltage does a dry cell give?", "steps": ["Zn/C chemistry.", "About 1.5 V.", "Select option D."], "subject": "chemistry", "text": "Answer: 1.5 V.\nSteps:\n1. Zn/C chemistry.\n2. About 1.5 V.\n3. Select option D.\nAnswer: (D)", "topic": "electrochemistry"}
{"answer": "The oxygen mass is 16.00 g, from 0.500 mol times 32.00 g/mol.", "choices": null, "id": "che_0900", "kind": "worked_example", "lang": "en", "question": "What mass of O2 comes from 2.00 mol of electrons?", "steps": ["4 e- give 1 O2: 0.500 mol.", "Multiply: 0.500 x 32.00.", "Mass = 16.00 g."], "subject": "chemistry", "text": "Answer: 16.00 g.\nSteps:\n1. 4 e- give 1 O2: 0.500 mol.\n2. Multiply: 0.500 x 32.00.\n3. Mass = 16.00 g.", "topic": "electrochemistry"}
{"answer": "Yields fall short from incomplete reaction, side products, and handling losses.", "choices": null, "id": "che_0901", "kind": "concept", "lang": "en", "question": "Why is actual yield below theoretical?", "steps": ["Reactions may not finish.", "Side products consume feed.", "Transfers lose material."], "subject": "chemistry", "text": "Answer: Incomplete, side, lost.\nSteps:\n1. Reactions may not finish.\n2. Side products consume feed.\n3. Transfers lose material.", "topic": "stoichiometry"}
{"answer": "Potassium nitrate totals 101.10 g/mol from K, N, and 3 O.", "choices": {"A": "85.10 g/mol", "B": "69.10 g/mol", "C": "39.10 g/mol", "D": "101.10 g/mol"}, "id": "che_0902", "kind": "multiple_choice", "lang": "en", "question": "What is the molar mass of KNO3?", "steps": ["39.10 + 14.01 + 48.00.", "Total 101.10.", "Select option D."], "subject": "chemistry", "text": "Answer: 101.10 g/mol.\nSteps:\n1. 39.10 + 14.01 + 48.00.\n2. Total 101.10.\n3. Select option D.\nAnswer: (D)", "topic": "stoichiometry"}
{"answer": "The mass is 48.05 g, from 0.750 mol times 64.06 g/mol.", "choices": null, "id": "che_0903", "kind": "worked_example", "lang": "en", "question": "What mass is 0.750 mol of SO2 (M = 64.06 g/mol)?", "steps": ["Write: m = 0.750 x 64.06.", "Multiply.", "m = 48.05 g."], "subject": "chemistry", "text": "Answer: 48.05 g.\nSteps:\n1. Write: m = 0.750 x 64.06.\n2. Multiply.\n3. m = 48.05 g.", "topic": "stoichiometry"}
{"answer": "Procentuální výtěžek je podíl skutečného a teoretického výtěžku krát sto.", "choices": null, "id": "che_0904", "kind": "concept", "lang": "cs", "question": "Co je procentuální výtěžek?", "steps": ["Skutečný děleno teoretickým.", "Krát 100 procent.", "Vždy pod 100 %."], "subject": "chemistry", "text": "Answer: Podíl výtěžků krát 100.\nSteps:\n1. Skutečný děleno teoretickým.\n2. Krát 100 procent.\n3. Vždy pod 100 %.", "topic": "stoichiometry"}
{"answer": "There are 0.448 mol, from 25.0 g divided by 55.845 g/mol.", "choices": null, "id": "che_0905", "kind": "worked_example", "lang": "en", "question": "How many moles are in 25.0 g of iron (M = 55.845 g/mol)?", "steps": ["Write: n = 25.0/55.845.", "Divide.", "n = 0.448 mol."], "subject": "chemistry", "text": "Answer: 0.448 mol.\nSteps:\n1. Write: n = 25.0/55.845.\n2. Divide.\n3. n = 0.448 mol.", "topic": "stoichiometry"}
{"answer": "The balanced equation is 2Cu + O2 -> 2CuO.", "choices": {"A": "1, 1, 1", "B": "2, 1, 2", "C": "1, 2, 2", "D": "2, 2, 2"}, "id": "che_0906", "kind": "multiple_choice", "lang": "en", "question": "What coefficients balance Cu + O2 -> CuO?", "steps": ["Cu: 2 each side.", "O: 2 each side.", "Select option B."], "subject": "chemistry", "text": "Answer: 2, 1, 2.\nSteps:\n1. Cu: 2 each side.\n2. O: 2 each side.\n3. Select option B.\nAnswer: (B)", "topic": "stoichiometry"}
{"answer": "Find the limiting reactant first, then subtract its need from the excess start.", "choices": null, "id": "che_0907", "kind": "concept", "lang": "en", "question": "How is leftover excess reactant found?", "steps": ["Identify limiting reactant.", "Compute excess consumed.", "Subtract from initial."], "subject": "chemistry", "text": "Answer: Initial minus consumed.\nSteps:\n1. Identify limiting reactant.\n2. Compute excess consumed.\n3. Subtract from initial.", "topic": "stoichiometry"}
{"answer": "The water mass is 35.74 g, from 1.984 mol times 18.015 g/mol.", "choices": null, "id": "che_0908", "kind": "worked_example", "lang": "en", "question": "What mass of H2O forms from 4.00 g H2 with excess O2?", "steps": ["Moles H2 = 4.00/2.016 = 1.984.", "Moles water = 1.984.", "Mass = 1.984 x 18.015 = 35.74 g."], "subject": "chemistry", "text": "Answer: 35.74 g.\nSteps:\n1. Moles H2 = 4.00/2.016 = 1.984.\n2. Moles water = 1.984.\n3. Mass = 1.984 x 18.015 = 35.74 g.", "topic": "stoichiometry"}
{"answer": "Objem je 89,7 l, protože 4 krát 22,414 se rovná 89,656.", "choices": null, "id": "che_0909", "kind": "worked_example", "lang": "cs", "question": "Jaký objem mají 4 moly plynu za STP?", "steps": ["Napiš vzorec: V = 4 x 22,414.", "Vynásob.", "V = 89,7 l."], "subject": "chemistry", "text": "Answer: 89,7 l.\nSteps:\n1. Napiš vzorec: V = 4 x 22,414.\n2. Vynásob.\n3. V = 89,7 l.", "topic": "stoichiometry"}
{"answer": "The molarity is 0.50 M, from 2.00 mol divided by 4.00 L.", "choices": {"A": "8.0 M", "B": "2.0 M", "C": "0.50 M", "D": "0.25 M"}, "id": "che_0910", "kind": "multiple_choice", "lang": "en", "question": "What is the molarity of 2.00 mol in 4.00 L?", "steps": ["Write: M = 2.00/4.00.", "Divide: 0.50.", "Select option C."], "subject": "chemistry", "text": "Answer: 0.50 M.\nSteps:\n1. Write: M = 2.00/4.00.\n2. Divide: 0.50.\n3. Select option C.\nAnswer: (C)", "topic": "stoichiometry"}
{"answer": "Dimensional analysis chains conversion factors so units cancel to the target.", "choices": null, "id": "che_0911", "kind": "concept", "lang": "en", "question": "What is dimensional analysis?", "steps": ["Start with given units.", "Multiply by ratios.", "Cancel to target units."], "subject": "chemistry", "text": "Answer: Unit-cancelling conversions.\nSteps:\n1. Start with given units.\n2. Multiply by ratios.\n3. Cancel to target units.", "topic": "stoichiometry"}
{"answer": "The pH scale runs 0 to 14, with 7 neutral at 25 C.", "choices": null, "id": "che_0912", "kind": "concept", "lang": "en", "question": "What is the pH scale?", "steps": ["0 to 14 range.", "Below 7 acidic.", "Above 7 basic."], "subject": "chemistry", "text": "Answer: 0-14 acidity scale.\nSteps:\n1. 0 to 14 range.\n2. Below 7 acidic.\n3. Above 7 basic.", "topic": "acids_bases"}
{"answer": "Two pH units mean 10 squared, or 100 times the acidity.", "choices": {"A": "2 times", "B": "100 times", "C": "1000 times", "D": "Equal"}, "id": "che_0913", "kind": "multiple_choice", "lang": "en", "question": "How much more acidic is pH 3 than pH 5?", "steps": ["Difference is 2 units.", "Each unit is 10x.", "Select option B."], "subject": "chemistry", "text": "Answer: 100 times.\nSteps:\n1. Difference is 2 units.\n2. Each unit is 10x.\n3. Select option B.\nAnswer: (B)", "topic": "acids_bases"}
{"answer": "The pH is 1.22, from -log(0.060).", "choices": null, "id": "che_0914", "kind": "worked_example", "lang": "en", "question": "Compute the pH of 0.060 M HCl.", "steps": ["[H+] = 0.060 M.", "pH = -log(0.060).", "pH = 1.22."], "subject": "chemistry", "text": "Answer: 1.22.\nSteps:\n1. [H+] = 0.060 M.\n2. pH = -log(0.060).\n3. pH = 1.22.", "topic": "acids_bases"}
{"answer": "Stupnice pH měří kyselost od 0 do 14, neutrální je 7.", "choices": null, "id": "che_0915", "kind": "concept", "lang": "cs", "question": "Co je stupnice pH?", "steps": ["Rozsah 0 až 14.", "Pod 7 kyselé.", "Nad 7 zásadité."], "subject": "chemistry", "text": "Answer: Škála kyselosti 0-14.\nSteps:\n1. Rozsah 0 až 14.\n2. Pod 7 kyselé.\n3. Nad 7 zásadité.", "topic": "acids_bases"}
{"answer": "The concentration is 3.16 x 10^-9 M, from 10 raised to -8.50.", "choices": null, "id": "che_0916", "kind": "worked_example", "lang": "en", "question": "A solution has pH 8.50. Compute [H+].", "steps": ["Write: [H+] = 10^(-8.50).", "Evaluate.", "[H+] = 3.16 x 10^-9 M."], "subject": "chemistry", "text": "Answer: 3.16 x 10^-9 M.\nSteps:\n1. Write: [H+] = 10^(-8.50).\n2. Evaluate.\n3. [H+] = 3.16 x 10^-9 M.", "topic": "acids_bases"}
{"answer": "Adding a proton to HPO4(2-) gives H2PO4-.", "choices": {"A": "H2PO4(-)", "B": "PO4(3-)", "C": "H3PO4", "D": "H2O"}, "id": "che_0917", "kind": "multiple_choice", "lang": "en", "question": "What is the conjugate acid of HPO4(2-)?", "steps": ["Add one H+.", "Result is H2PO4-.", "Select option A."], "subject": "chemistry", "text": "Answer: H2PO4-.\nSteps:\n1. Add one H+.\n2. Result is H2PO4-.\n3. Select option A.\nAnswer: (A)", "topic": "acids_bases"}
{"answer": "Antacids are weak bases that neutralize excess stomach HCl.", "choices": null, "id": "che_0918", "kind": "concept", "lang": "en", "question": "How do antacids work?", "steps": ["Stomach holds HCl.", "Base neutralizes it.", "pH rises, pain eases."], "subject": "chemistry", "text": "Answer: Neutralize stomach acid.\nSteps:\n1. Stomach holds HCl.\n2. Base neutralizes it.\n3. pH rises, pain eases.", "topic": "acids_bases"}
{"answer": "There are 10.0 mmol, from 5.00 mL times 2.00 M.", "choices": null, "id": "che_0919", "kind": "worked_example", "lang": "en", "question": "How many millimoles are in 5.00 mL of 2.00 M acid?", "steps": ["Write: mmol = 5.00 x 2.00.", "Multiply.", "mmol = 10.0."], "subject": "chemistry", "text": "Answer: 10.0 mmol.\nSteps:\n1. Write: mmol = 5.00 x 2.00.\n2. Multiply.\n3. mmol = 10.0.", "topic": "acids_bases"}
{"answer": "pH je 1,30, protože -log(0,05) = 1,30.", "choices": null, "id": "che_0920", "kind": "worked_example", "lang": "cs", "question": "Vypočítej pH roztoku 0,05 M HNO3.", "steps": ["HNO3 disociuje plně.", "pH = -log(0,05).", "pH = 1,30."], "subject": "chemistry", "text": "Answer: 1,30.\nSteps:\n1. HNO3 disociuje plně.\n2. pH = -log(0,05).\n3. pH = 1,30.", "topic": "acids_bases"}
{"answer": "Soap solutions release OH- from fatty acid salts, so they are basic.", "choices": {"A": "Acidic", "B": "Neutral", "C": "Basic", "D": "Cannot tell"}, "id": "che_0921", "kind": "multiple_choice", "lang": "en", "question": "Is soap solution acidic or basic?", "steps": ["Soap is weak-acid salt.", "Anion hydrolyzes.", "Select option C."], "subject": "chemistry", "text": "Answer: Basic.\nSteps:\n1. Soap is weak-acid salt.\n2. Anion hydrolyzes.\n3. Select option C.\nAnswer: (C)", "topic": "acids_bases"}
{"answer": "Dissolved CO2 forms carbonic acid that lowers ocean pH.", "choices": null, "id": "che_0922", "kind": "concept", "lang": "en", "question": "What is ocean acidification?", "steps": ["CO2 dissolves in water.", "Carbonic acid forms.", "pH falls, shells weaken."], "subject": "chemistry", "text": "Answer: CO2 lowering ocean pH.\nSteps:\n1. CO2 dissolves in water.\n2. Carbonic acid forms.\n3. pH falls, shells weaken.", "topic": "acids_bases"}
{"answer": "Group 2 metals always take oxidation state +2 in compounds.", "choices": null, "id": "che_0923", "kind": "concept", "lang": "en", "question": "What oxidation state do Group 2 metals take?", "steps": ["Group 2 loses two electrons.", "State is +2 always.", "Example: Mg in MgO."], "subject": "chemistry", "text": "Answer: +2 always.\nSteps:\n1. Group 2 loses two electrons.\n2. State is +2 always.\n3. Example: Mg in MgO.", "topic": "redox"}
{"answer": "Magnesium is +2, balanced by two chlorides at -1.", "choices": {"A": "+2", "B": "+1", "C": "0", "D": "-2"}, "id": "che_0924", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of Mg in MgCl2?", "steps": ["Cl is -1 each.", "Solve: Mg - 2 = 0.", "Mg = +2; select A."], "subject": "chemistry", "text": "Answer: +2.\nSteps:\n1. Cl is -1 each.\n2. Solve: Mg - 2 = 0.\n3. Mg = +2; select A.\nAnswer: (A)", "topic": "redox"}
{"answer": "Arsenic is +5, since 3(+1) + As + 4(-2) = 0.", "choices": null, "id": "che_0925", "kind": "worked_example", "lang": "en", "question": "Find the oxidation number of As in H3AsO4.", "steps": ["Assign H +1 and O -2.", "Equation: 3 + As - 8 = 0.", "As = +5."], "subject": "chemistry", "text": "Answer: +5.\nSteps:\n1. Assign H +1 and O -2.\n2. Equation: 3 + As - 8 = 0.\n3. As = +5.", "topic": "redox"}
{"answer": "Redukce je přijetí elektronů spojené se snížením oxidačního čísla.", "choices": null, "id": "che_0926", "kind": "concept", "lang": "cs", "question": "Co je redukce?", "steps": ["Příjem elektronů.", "Pokles oxidačního čísla.", "Příklad: Cu2+ na Cu."], "subject": "chemistry", "text": "Answer: Příjem elektronů.\nSteps:\n1. Příjem elektronů.\n2. Pokles oxidačního čísla.\n3. Příklad: Cu2+ na Cu.", "topic": "redox"}
{"answer": "The balanced equation is 2Ba + O2 -> 2BaO.", "choices": null, "id": "che_0927", "kind": "worked_example", "lang": "en", "question": "Balance: Ba + O2 -> BaO.", "steps": ["Balance O with 2 BaO.", "Balance Ba with 2 Ba.", "Result: 2Ba + O2 -> 2BaO."], "subject": "chemistry", "text": "Answer: 2Ba + O2 -> 2BaO.\nSteps:\n1. Balance O with 2 BaO.\n2. Balance Ba with 2 Ba.\n3. Result: 2Ba + O2 -> 2BaO.", "topic": "redox"}
{"answer": "Hydrogen goes from 0 to +1, so it is oxidized.", "choices": {"A": "Cl2", "B": "H2", "C": "HCl", "D": "None"}, "id": "che_0928", "kind": "multiple_choice", "lang": "en", "question": "In H2 + Cl2 -> 2HCl, what is oxidized?", "steps": ["H goes 0 to +1.", "That is oxidation.", "Select option B."], "subject": "chemistry", "text": "Answer: H2.\nSteps:\n1. H goes 0 to +1.\n2. That is oxidation.\n3. Select option B.\nAnswer: (B)", "topic": "redox"}
{"answer": "Photosynthesis reduces CO2 to sugar while water is oxidized to O2.", "choices": null, "id": "che_0929", "kind": "concept", "lang": "en", "question": "How is photosynthesis a redox process?", "steps": ["CO2 gains electrons.", "Water loses them.", "Light powers the transfer."], "subject": "chemistry", "text": "Answer: CO2 reduced, water oxidized.\nSteps:\n1. CO2 gains electrons.\n2. Water loses them.\n3. Light powers the transfer.", "topic": "redox"}
{"answer": "Two electrons are gained as I2 becomes 2I-.", "choices": null, "id": "che_0930", "kind": "worked_example", "lang": "en", "question": "How many electrons are gained in I2 -> 2I-?", "steps": ["Each I goes 0 to -1.", "Two I gain 1 each.", "Total gained = 2."], "subject": "chemistry", "text": "Answer: 2 electrons.\nSteps:\n1. Each I goes 0 to -1.\n2. Two I gain 1 each.\n3. Total gained = 2.", "topic": "redox"}
{"answer": "Olovo má oxidační číslo +4, protože Pb + 2(-2) = 0.", "choices": null, "id": "che_0931", "kind": "worked_example", "lang": "cs", "question": "Urči oxidační číslo olova v PbO2.", "steps": ["Přiřaď O -2.", "Rovnice: Pb - 4 = 0.", "Pb = +4."], "subject": "chemistry", "text": "Answer: +4.\nSteps:\n1. Přiřaď O -2.\n2. Rovnice: Pb - 4 = 0.\n3. Pb = +4.", "topic": "redox"}
{"answer": "Potassium is +1 as in all its compounds.", "choices": {"A": "-1", "B": "0", "C": "+1", "D": "+2"}, "id": "che_0932", "kind": "multiple_choice", "lang": "en", "question": "What is the oxidation state of K in KO2?", "steps": ["Alkali metals are +1.", "Applies here too.", "Select option C."], "subject": "chemistry", "text": "Answer: +1.\nSteps:\n1. Alkali metals are +1.\n2. Applies here too.\n3. Select option C.\nAnswer: (C)", "topic": "redox"}
{"answer": "Respiration oxidizes glucose to CO2 while oxygen is reduced to water.", "choices": null, "id": "che_0933", "kind": "concept", "lang": "en", "question": "How is respiration a redox process?", "steps": ["Glucose loses electrons.", "Oxygen gains them.", "Energy is released."], "subject": "chemistry", "text": "Answer: Glucose oxidized, O2 reduced.\nSteps:\n1. Glucose loses electrons.\n2. Oxygen gains them.\n3. Energy is released.", "topic": "redox"}
{"answer": "Melting, vaporizing, and dissolving salts are common endothermic examples.", "choices": null, "id": "che_0934", "kind": "concept", "lang": "en", "question": "What are examples of endothermic processes?", "steps": ["Ice melting absorbs heat.", "Water boiling absorbs heat.", "Cold packs use salt dissolving."], "subject": "chemistry", "text": "Answer: Melting, boiling, cold packs.\nSteps:\n1. Ice melting absorbs heat.\n2. Water boiling absorbs heat.\n3. Cold packs use salt dissolving.", "topic": "thermochemistry"}
{"answer": "Melting absorbs heat from the surroundings.", "choices": {"A": "Heat in", "B": "Heat out", "C": "No heat", "D": "Work only"}, "id": "che_0935", "kind": "multiple_choice", "lang": "en", "question": "Does ice melting need heat in or out?", "steps": ["Bonds break.", "Breaking needs energy.", "Select option A."], "subject": "chemistry", "text": "Answer: Heat in.\nSteps:\n1. Bonds break.\n2. Breaking needs energy.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "The heat is 18.8 kJ, from 50 x 4.184 x 90 J.", "choices": null, "id": "che_0936", "kind": "worked_example", "lang": "en", "question": "How much heat warms 50 g of water from 10 C to 100 C?", "steps": ["ΔT = 100 - 10 = 90 C.", "q = 50 x 4.184 x 90.", "q = 18,828 J = 18.8 kJ."], "subject": "chemistry", "text": "Answer: 18.8 kJ.\nSteps:\n1. ΔT = 100 - 10 = 90 C.\n2. q = 50 x 4.184 x 90.\n3. q = 18,828 J = 18.8 kJ.", "topic": "thermochemistry"}
{"answer": "Tepelná kapacita tělesa je teplo potřebné k ohřátí o 1 °C.", "choices": null, "id": "che_0937", "kind": "concept", "lang": "cs", "question": "Co je tepelná kapacita tělesa?", "steps": ["Teplo na 1 °C.", "Závisí na hmotnosti.", "Jednotka J/°C."], "subject": "chemistry", "text": "Answer: Teplo na 1 °C.\nSteps:\n1. Teplo na 1 °C.\n2. Závisí na hmotnosti.\n3. Jednotka J/°C.", "topic": "thermochemistry"}
{"answer": "The rise is 1.20 C, from 500 J divided by (100 x 4.184).", "choices": null, "id": "che_0938", "kind": "worked_example", "lang": "en", "question": "100 g of water gains 500 J. Find ΔT (c = 4.184 J/gC).", "steps": ["Write: ΔT = 500/(100 x 4.184).", "Divide: 500/418.4.", "ΔT = 1.20 C."], "subject": "chemistry", "text": "Answer: 1.20 C.\nSteps:\n1. Write: ΔT = 500/(100 x 4.184).\n2. Divide: 500/418.4.\n3. ΔT = 1.20 C.", "topic": "thermochemistry"}
{"answer": "One calorie equals 4.184 joules exactly.", "choices": {"A": "1 J", "B": "4.184 J", "C": "1000 J", "D": "0.239 J"}, "id": "che_0939", "kind": "multiple_choice", "lang": "en", "question": "How many joules are in one calorie?", "steps": ["Definition: 4.184 J.", "Eliminate others.", "Select option B."], "subject": "chemistry", "text": "Answer: 4.184 J.\nSteps:\n1. Definition: 4.184 J.\n2. Eliminate others.\n3. Select option B.\nAnswer: (B)", "topic": "thermochemistry"}
{"answer": "A food Calorie is one kilocalorie, or 1000 chemistry calories.", "choices": null, "id": "che_0940", "kind": "concept", "lang": "en", "question": "What is a food Calorie?", "steps": ["Capital C matters.", "Equals 1 kcal.", "Equals 4184 J."], "subject": "chemistry", "text": "Answer: One kilocalorie.\nSteps:\n1. Capital C matters.\n2. Equals 1 kcal.\n3. Equals 4184 J.", "topic": "thermochemistry"}
{"answer": "The ΔH is -300 kJ, from -500 minus -200 kJ.", "choices": null, "id": "che_0941", "kind": "worked_example", "lang": "en", "question": "Products total -500 kJ and reactants -200 kJ. Find ΔH.", "steps": ["Write: ΔH = products - reactants.", "Substitute: -500 - (-200).", "ΔH = -300 kJ."], "subject": "chemistry", "text": "Answer: -300 kJ.\nSteps:\n1. Write: ΔH = products - reactants.\n2. Substitute: -500 - (-200).\n3. ΔH = -300 kJ.", "topic": "thermochemistry"}
{"answer": "Potřebné teplo je 8368 J, protože 80 x 4,184 x 25 se rovná 8368.", "choices": null, "id": "che_0942", "kind": "worked_example", "lang": "cs", "question": "Kolik tepla ohřeje 80 g vody o 25 °C?", "steps": ["Napiš vzorec: q = 80 x 4,184 x 25.", "Vynásob.", "q = 8368 J."], "subject": "chemistry", "text": "Answer: 8368 J.\nSteps:\n1. Napiš vzorec: q = 80 x 4,184 x 25.\n2. Vynásob.\n3. q = 8368 J.", "topic": "thermochemistry"}
{"answer": "Rising universe entropy marks spontaneous processes.", "choices": {"A": "Spontaneity", "B": "Speed", "C": "Color", "D": "Mass"}, "id": "che_0943", "kind": "multiple_choice", "lang": "en", "question": "What does ΔS of the universe determine?", "steps": ["Second law criterion.", "Positive means spontaneous.", "Select option A."], "subject": "chemistry", "text": "Answer: Spontaneity.\nSteps:\n1. Second law criterion.\n2. Positive means spontaneous.\n3. Select option A.\nAnswer: (A)", "topic": "thermochemistry"}
{"answer": "The third law states a perfect crystal has zero entropy at 0 K.", "choices": null, "id": "che_0944", "kind": "concept", "lang": "en", "question": "What is the third law of thermodynamics?", "steps": ["Perfect order at 0 K.", "One microstate only.", "Entropy equals zero."], "subject": "chemistry", "text": "Answer: Zero entropy at 0 K.\nSteps:\n1. Perfect order at 0 K.\n2. One microstate only.\n3. Entropy equals zero.", "topic": "thermochemistry"}
{"answer": "Isopropyl and tert-butyl are common branched alkyl names.", "choices": null, "id": "che_0945", "kind": "concept", "lang": "en", "question": "What are isopropyl and tert-butyl?", "steps": ["Isopropyl: 3 carbons branched.", "Tert-butyl: 4 carbons branched.", "Retained common names."], "subject": "chemistry", "text": "Answer: Branched alkyl groups.\nSteps:\n1. Isopropyl: 3 carbons branched.\n2. Tert-butyl: 4 carbons branched.\n3. Retained common names.", "topic": "organic_naming"}
{"answer": "Isopropyl attaches through the middle carbon, making it 2-propyl.", "choices": {"A": "1-propyl", "B": "Ethyl", "C": "2-propyl", "D": "Butyl"}, "id": "che_0946", "kind": "multiple_choice", "lang": "en", "question": "What is isopropyl systematically?", "steps": ["Three-carbon branch.", "Middle attachment.", "Select option C."], "subject": "chemistry", "text": "Answer: 2-propyl.\nSteps:\n1. Three-carbon branch.\n2. Middle attachment.\n3. Select option C.\nAnswer: (C)", "topic": "organic_naming"}
{"answer": "The name is 2,3-dimethylpentane: methyls on carbons 2 and 3.", "choices": null, "id": "che_0947", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2CH(CH3)CH(CH3)2.", "steps": ["Longest chain: 5 = pentane.", "Methyls on carbons 2 and 3.", "Name: 2,3-dimethylpentane."], "subject": "chemistry", "text": "Answer: 2,3-dimethylpentane.\nSteps:\n1. Longest chain: 5 = pentane.\n2. Methyls on carbons 2 and 3.\n3. Name: 2,3-dimethylpentane.", "topic": "organic_naming"}
{"answer": "Alkyl je uhlovodíkový zbytek vzniklý odtržením vodíku z alkanu.", "choices": null, "id": "che_0948", "kind": "concept", "lang": "cs", "question": "Co je alkyl?", "steps": ["Alkan bez jednoho H.", "Obecný vzorec CnH2n+1.", "Příklad: methyl, ethyl."], "subject": "chemistry", "text": "Answer: Zbytek alkanu.\nSteps:\n1. Alkan bez jednoho H.\n2. Obecný vzorec CnH2n+1.\n3. Příklad: methyl, ethyl.", "topic": "organic_naming"}
{"answer": "The name is pentane: five carbons in a straight chain.", "choices": null, "id": "che_0949", "kind": "worked_example", "lang": "en", "question": "Name CH3CH2CH2CH2CH3.", "steps": ["Count 5 carbons.", "Single bonds only.", "Name: pentane."], "subject": "chemistry", "text": "Answer: Pentane.\nSteps:\n1. Count 5 carbons.\n2. Single bonds only.\n3. Name: pentane.", "topic": "organic_naming"}
{"answer": "Pentane has five carbon atoms.", "choices": {"A": "4", "B": "5", "C": "6", "D": "3"}, "id": "che_0950", "kind": "multiple_choice", "lang": "en", "question": "How many carbons are in pentane?", "steps": ["Pent- means five.", "Straight chain.", "Select option B."], "subject": "chemistry", "text": "Answer: 5.\nSteps:\n1. Pent- means five.\n2. Straight chain.\n3. Select option B.\nAnswer: (B)", "topic": "organic_naming"}
{"answer": "Ring substituents take lowest numbers around the benzene.", "choices": null, "id": "che_0951", "kind": "concept", "lang": "en", "question": "How are substituted benzenes numbered?", "steps": ["First group at carbon 1.", "Lowest set for rest.", "Or use ortho/meta/para."], "subject": "chemistry", "text": "Answer: Lowest numbers on ring.\nSteps:\n1. First group at carbon 1.\n2. Lowest set for rest.\n3. Or use ortho/meta/para.", "topic": "organic_naming"}
{"answer": "The name is chlorobenzene: chlorine on a benzene ring.", "choices": null, "id": "che_0952", "kind": "worked_example", "lang": "en", "question": "Name C6H5Cl.", "steps": ["Benzene ring present.", "Chlorine substituent.", "Name: chlorobenzene."], "subject": "chemistry", "text": "Answer: Chlorobenzene.\nSteps:\n1. Benzene ring present.\n2. Chlorine substituent.\n3. Name: chlorobenzene.", "topic": "organic_naming"}
{"answer": "C2H6 je ethan.", "choices": null, "id": "che_0953", "kind": "worked_example", "lang": "cs", "question": "Pojmenuj sloučeninu C2H6.", "steps": ["Dva uhlíky.", "Jen jednoduché vazby.", "Název: ethan."], "subject": "chemistry", "text": "Answer: Ethan.\nSteps:\n1. Dva uhlíky.\n2. Jen jednoduché vazby.\n3. Název: ethan.", "topic": "organic_naming"}
{"answer": "Para means opposite 1,4 positions on a benzene ring.", "choices": {"A": "1,2 positions", "B": "1,3 positions", "C": "1,5 positions", "D": "1,4 positions"}, "id": "che_0954", "kind": "multiple_choice", "lang": "en", "question": "What does para- mean on benzene?", "steps": ["Para means opposite.", "That is 1,4.", "Select option D."], "subject": "chemistry", "text": "Answer: 1,4 positions.\nSteps:\n1. Para means opposite.\n2. That is 1,4.\n3. Select option D.\nAnswer: (D)", "topic": "organic_naming"}
{"answer": "Ortho is 1,2, meta is 1,3, and para is 1,4 on benzene.", "choices": null, "id": "che_0955", "kind": "concept", "lang": "en", "question": "What do ortho, meta, and para mean?", "steps": ["Ortho: adjacent 1,2.", "Meta: separated 1,3.", "Para: opposite 1,4."], "subject": "chemistry", "text": "Answer: 1,2, 1,3, and 1,4.\nSteps:\n1. Ortho: adjacent 1,2.\n2. Meta: separated 1,3.\n3. Para: opposite 1,4.", "topic": "organic_naming"}
{"answer": "Mechanisms break reactions into elementary steps with intermediates.", "choices": null, "id": "che_0956", "kind": "concept", "lang": "en", "question": "What is a reaction mechanism?", "steps": ["Sequence of steps.", "Intermediates appear.", "Sum gives overall reaction."], "subject": "chemistry", "text": "Answer: Step-by-step pathway.\nSteps:\n1. Sequence of steps.\n2. Intermediates appear.\n3. Sum gives overall reaction.", "topic": "organic_mechanisms"}
{"answer": "The slowest step limits the overall reaction rate.", "choices": {"A": "Slowest step", "B": "Fastest step", "C": "First step", "D": "Last step"}, "id": "che_0957", "kind": "multiple_choice", "lang": "en", "question": "What is the rate-determining step?", "steps": ["Bottleneck of pathway.", "Slowest step rules.", "Select option A."], "subject": "chemistry", "text": "Answer: Slowest step.\nSteps:\n1. Bottleneck of pathway.\n2. Slowest step rules.\n3. Select option A.\nAnswer: (A)", "topic": "organic_mechanisms"}
{"answer": "The SN1 rate triples to 3x because rate equals k[RX].", "choices": null, "id": "che_0958", "kind": "worked_example", "lang": "en", "question": "SN1 rate = k[RX] with tripled [RX]. What is the new rate?", "steps": ["Write: rate = k x 3[RX].", "Factor: 3 x k[RX].", "Rate becomes 3x."], "subject": "chemistry", "text": "Answer: 3x.\nSteps:\n1. Write: rate = k x 3[RX].\n2. Factor: 3 x k[RX].\n3. Rate becomes 3x.", "topic": "organic_mechanisms"}
{"answer": "Elementární reakce je jeden krok mechanismu bez meziproduktů.", "choices": null, "id": "che_0959", "kind": "concept", "lang": "cs", "question": "Co je elementární reakce?", "steps": ["Jeden krok mechanismu.", "Přímá přeměna.", "Součet dá celkovou reakci."], "subject": "chemistry", "text": "Answer: Jeden krok mechanismu.\nSteps:\n1. Jeden krok mechanismu.\n2. Přímá přeměna.\n3. Součet dá celkovou reakci.", "topic": "organic_mechanisms"}
{"answer": "The product is 2-bromobutane, with Br on carbon 2.", "choices": null, "id": "che_0960", "kind": "worked_example", "lang": "en", "question": "What is the HBr addition product of 2-butene?", "steps": ["Symmetric double bond.", "H and Br add across.", "Product: 2-bromobutane."], "subject": "chemistry", "text": "Answer: 2-bromobutane.\nSteps:\n1. Symmetric double bond.\n2. H and Br add across.\n3. Product: 2-bromobutane.", "topic": "organic_mechanisms"}
{"answer": "Electrophilic addition passes through a carbocation intermediate.", "choices": {"A": "Radical", "B": "Carbocation", "C": "Carbanion", "D": "Epoxide"}, "id": "che_0961", "kind": "multiple_choice", "lang": "en", "question": "What intermediate forms in electrophilic addition?", "steps": ["Electrophile adds first.", "Positive carbon remains.", "Select option B."], "subject": "chemistry", "text": "Answer: Carbocation.\nSteps:\n1. Electrophile adds first.\n2. Positive carbon remains.\n3. Select option B.\nAnswer: (B)", "topic": "organic_mechanisms"}
{"answer": "Radical substitution cycles through initiation, propagation, and termination.", "choices": null, "id": "che_0962", "kind": "concept", "lang": "en", "question": "What are the stages of radical substitution?", "steps": ["Initiation makes radicals.", "Propagation cycles them.", "Termination pairs them."], "subject": "chemistry", "text": "Answer: Initiation to termination.\nSteps:\n1. Initiation makes radicals.\n2. Propagation cycles them.\n3. Termination pairs them.", "topic": "organic_mechanisms"}
{"answer": "Bromination gives bromomethane plus HBr via a radical chain.", "choices": null, "id": "che_0963", "kind": "worked_example", "lang": "en", "question": "What are the products of methane bromination (Br2, light)?", "steps": ["Br radical abstracts H.", "Methyl radical takes Br.", "Products: CH3Br + HBr."], "subject": "chemistry", "text": "Answer: CH3Br + HBr.\nSteps:\n1. Br radical abstracts H.\n2. Methyl radical takes Br.\n3. Products: CH3Br + HBr.", "topic": "organic_mechanisms"}
{"answer": "Spalováním methanu vzniká CO2 a H2O.", "choices": null, "id": "che_0964", "kind": "worked_example", "lang": "cs", "question": "Jaké produkty dá spalování methanu?", "steps": ["Uhlík oxiduje na CO2.", "Vodík na H2O.", "Produkty: CO2 a H2O."], "subject": "chemistry", "text": "Answer: CO2 a H2O.\nSteps:\n1. Uhlík oxiduje na CO2.\n2. Vodík na H2O.\n3. Produkty: CO2 a H2O.", "topic": "organic_mechanisms"}
{"answer": "Complete combustion of hydrocarbons yields carbon dioxide and water.", "choices": {"A": "CO only", "B": "C plus H2", "C": "O2", "D": "CO2 plus H2O"}, "id": "che_0965", "kind": "multiple_choice", "lang": "en", "question": "What are complete combustion products?", "steps": ["C burns to CO2.", "H burns to H2O.", "Select option D."], "subject": "chemistry", "text": "Answer: CO2 plus H2O.\nSteps:\n1. C burns to CO2.\n2. H burns to H2O.\n3. Select option D.\nAnswer: (D)", "topic": "organic_mechanisms"}
{"answer": "Higher temperature lets more molecules clear the activation barrier.", "choices": null, "id": "che_0966", "kind": "concept", "lang": "en", "question": "Why does heating speed reactions?", "steps": ["Molecules move faster.", "More exceed barrier.", "Rate rises sharply."], "subject": "chemistry", "text": "Answer: More clear the barrier.\nSteps:\n1. Molecules move faster.\n2. More exceed barrier.\n3. Rate rises sharply.", "topic": "organic_mechanisms"}
{"answer": "The Haber process compromises: high pressure, moderate heat, iron catalyst.", "choices": null, "id": "che_0967", "kind": "concept", "lang": "en", "question": "What conditions suit the Haber process?", "steps": ["High pressure favors NH3.", "Moderate heat balances rate.", "Iron catalyst speeds up."], "subject": "chemistry", "text": "Answer: High P, moderate T, iron.\nSteps:\n1. High pressure favors NH3.\n2. Moderate heat balances rate.\n3. Iron catalyst speeds up.", "topic": "equilibrium"}
{"answer": "High pressure with moderate temperature balances yield and rate.", "choices": {"A": "High P, moderate T", "B": "Low P, high T", "C": "Low P, low T", "D": "No catalyst"}, "id": "che_0968", "kind": "multiple_choice", "lang": "en", "question": "What conditions optimize Haber NH3 yield?", "steps": ["Pressure favors fewer moles.", "Too hot kills yield.", "Select option A."], "subject": "chemistry", "text": "Answer: High P, moderate T.\nSteps:\n1. Pressure favors fewer moles.\n2. Too hot kills yield.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "K is 8.0, from 0.50 divided by 0.25 squared.", "choices": null, "id": "che_0969", "kind": "worked_example", "lang": "en", "question": "For 2NO2 <-> N2O4 with [NO2] = 0.25 M and [N2O4] = 0.50 M, compute K.", "steps": ["Write: K = [N2O4]/[NO2]^2.", "Substitute: 0.50/0.0625.", "K = 8.0."], "subject": "chemistry", "text": "Answer: 8.0.\nSteps:\n1. Write: K = [N2O4]/[NO2]^2.\n2. Substitute: 0.50/0.0625.\n3. K = 8.0.", "topic": "equilibrium"}
{"answer": "Haberova-Boschova syntéza vyrábí amoniak z dusíku a vodíku.", "choices": null, "id": "che_0970", "kind": "concept", "lang": "cs", "question": "Co je Haberova-Boschova syntéza?", "steps": ["N2 + 3H2 na NH3.", "Vysoký tlak.", "Železný katalyzátor."], "subject": "chemistry", "text": "Answer: Výroba amoniaku.\nSteps:\n1. N2 + 3H2 na NH3.\n2. Vysoký tlak.\n3. Železný katalyzátor.", "topic": "equilibrium"}
{"answer": "Iron catalyzes the Haber reaction industrially.", "choices": {"A": "Pt", "B": "Fe", "C": "Ni", "D": "Cu"}, "id": "che_0971", "kind": "multiple_choice", "lang": "en", "question": "Which catalyst does the Haber process use?", "steps": ["Iron beds employed.", "Eliminate Pt, Ni, Cu.", "Select option B."], "subject": "chemistry", "text": "Answer: Fe.\nSteps:\n1. Iron beds employed.\n2. Eliminate Pt, Ni, Cu.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "The system is at equilibrium with no shift.", "choices": null, "id": "che_0972", "kind": "worked_example", "lang": "en", "question": "Q = 3.0 and K = 3.0. Which way does the system shift?", "steps": ["Compare: Q equals K.", "No excess either side.", "No shift."], "subject": "chemistry", "text": "Answer: No shift.\nSteps:\n1. Compare: Q equals K.\n2. No excess either side.\n3. No shift.", "topic": "equilibrium"}
{"answer": "Le Chatelier's principle predicts shifts opposing concentration, pressure, and heat changes.", "choices": null, "id": "che_0973", "kind": "concept", "lang": "en", "question": "What does Le Chatelier's principle summarize?", "steps": ["Stresses disturb balance.", "System opposes them.", "New balance results."], "subject": "chemistry", "text": "Answer: Opposition to stresses.\nSteps:\n1. Stresses disturb balance.\n2. System opposes them.\n3. New balance results.", "topic": "equilibrium"}
{"answer": "Systems relieve stress by shifting against it.", "choices": {"A": "Same shift", "B": "Stopping", "C": "Opposing shift", "D": "Explosion"}, "id": "che_0974", "kind": "multiple_choice", "lang": "en", "question": "How do systems answer stress?", "steps": ["Counteract the change.", "Shift opposes stress.", "Select option C."], "subject": "chemistry", "text": "Answer: Opposing shift.\nSteps:\n1. Counteract the change.\n2. Shift opposes stress.\n3. Select option C.\nAnswer: (C)", "topic": "equilibrium"}
{"answer": "Odebrání reaktantu posune rovnováhu doleva, k reaktantům.", "choices": null, "id": "che_0975", "kind": "worked_example", "lang": "cs", "question": "Kam se posune rovnováha po odebrání reaktantu?", "steps": ["Reaktantů je málo.", "Soustava je doplní.", "Posun doleva."], "subject": "chemistry", "text": "Answer: Doleva.\nSteps:\n1. Reaktantů je málo.\n2. Soustava je doplní.\n3. Posun doleva.", "topic": "equilibrium"}
{"answer": "Bigger volume lowers pressure, shifting toward two product moles.", "choices": null, "id": "che_0976", "kind": "worked_example", "lang": "en", "question": "Volume rises for PCl5 <-> PCl3 + Cl2. Which way is the shift?", "steps": ["Pressure drops.", "System favors more moles.", "Shifts right."], "subject": "chemistry", "text": "Answer: Shifts right.\nSteps:\n1. Pressure drops.\n2. System favors more moles.\n3. Shifts right.", "topic": "equilibrium"}
{"answer": "Low pressure favors the side with more gas moles.", "choices": {"A": "High P", "B": "Low P", "C": "High T", "D": "Catalyst"}, "id": "che_0977", "kind": "multiple_choice", "lang": "en", "question": "What favors the more-moles side?", "steps": ["More moles need room.", "Low pressure gives it.", "Select option B."], "subject": "chemistry", "text": "Answer: Low P.\nSteps:\n1. More moles need room.\n2. Low pressure gives it.\n3. Select option B.\nAnswer: (B)", "topic": "equilibrium"}
{"answer": "Heating an exothermic reaction lowers K as reactants gain favor.", "choices": null, "id": "che_0978", "kind": "concept", "lang": "en", "question": "How does temperature change K for exothermic reactions?", "steps": ["Heat acts as product.", "Warming shifts left.", "K shrinks."], "subject": "chemistry", "text": "Answer: K falls with temperature.\nSteps:\n1. Heat acts as product.\n2. Warming shifts left.\n3. K shrinks.", "topic": "equilibrium"}
{"answer": "Teplota je jediná veličina měnící hodnotu K.", "choices": null, "id": "che_0979", "kind": "concept", "lang": "cs", "question": "Jak teplota ovlivňuje rovnovážnou konstantu?", "steps": ["Jediná mění K.", "Endotermická: K roste.", "Exotermická: K klesá."], "subject": "chemistry", "text": "Answer: Jediná mění hodnotu K.\nSteps:\n1. Jediná mění K.\n2. Endotermická: K roste.\n3. Exotermická: K klesá.", "topic": "equilibrium"}
{"answer": "Warming shifts exothermic equilibrium left, shrinking K.", "choices": {"A": "Heating", "B": "Cooling", "C": "Pressure", "D": "Catalyst"}, "id": "che_0980", "kind": "multiple_choice", "lang": "en", "question": "What shrinks K of an exothermic reaction?", "steps": ["Heat is a product.", "Adding it shifts left.", "Select option A."], "subject": "chemistry", "text": "Answer: Heating.\nSteps:\n1. Heat is a product.\n2. Adding it shifts left.\n3. Select option A.\nAnswer: (A)", "topic": "equilibrium"}
{"answer": "The solubility is 1.12 x 10^-4 M, from (5.6 x 10^-12 / 4)^(1/3).", "choices": null, "id": "che_0981", "kind": "worked_example", "lang": "en", "question": "Mg(OH)2 has Ksp = 5.6 x 10^-12. Compute its molar solubility.", "steps": ["Write: Ksp = 4s^3.", "s^3 = 5.6 x 10^-12 / 4 = 1.4 x 10^-12.", "s = 1.12 x 10^-4 M."], "subject": "chemistry", "text": "Answer: 1.12 x 10^-4 M.\nSteps:\n1. Write: Ksp = 4s^3.\n2. s^3 = 5.6 x 10^-12 / 4 = 1.4 x 10^-12.\n3. s = 1.12 x 10^-4 M.", "topic": "equilibrium"}
{"answer": "PbI2 se nevysráží, protože Q = 1,0 x 10^-10 je pod Ksp = 7,1 x 10^-9.", "choices": null, "id": "che_0982", "kind": "worked_example", "lang": "cs", "question": "[Pb2+] = 1e-4 M a [I-] = 1e-3 M. Vysráží se PbI2 (Ksp = 7,1e-9)?", "steps": ["Q = 1e-4 x (1e-3)^2 = 1e-10.", "Porovnej: 1e-10 < 7,1e-9.", "Nevysráží se."], "subject": "chemistry", "text": "Answer: Ne, Q < Ksp.\nSteps:\n1. Q = 1e-4 x (1e-3)^2 = 1e-10.\n2. Porovnej: 1e-10 < 7,1e-9.\n3. Nevysráží se.", "topic": "equilibrium"}
{"answer": "Below Ksp the solution is unsaturated and holds all ions.", "choices": {"A": "Precipitate", "B": "Saturated", "C": "Supersaturated", "D": "Unsaturated"}, "id": "che_0983", "kind": "multiple_choice", "lang": "en", "question": "What does Q < Ksp mean?", "steps": ["Ions below limit.", "More could dissolve.", "Select option D."], "subject": "chemistry", "text": "Answer: Unsaturated.\nSteps:\n1. Ions below limit.\n2. More could dissolve.\n3. Select option D.\nAnswer: (D)", "topic": "equilibrium"}
{"answer": "Electrolysis plates metals, splits water, and refines aluminum.", "choices": null, "id": "che_0984", "kind": "concept", "lang": "en", "question": "What is electrolysis used for?", "steps": ["Plating coats objects.", "Splitting makes gases.", "Refining purifies metals."], "subject": "chemistry", "text": "Answer: Plating, splitting, refining.\nSteps:\n1. Plating coats objects.\n2. Splitting makes gases.\n3. Refining purifies metals.", "topic": "electrochemistry"}
{"answer": "Aluminum is won by electrolyzing molten cryolite ore.", "choices": {"A": "Electrolysis", "B": "Smelting", "C": "Distillation", "D": "Filtration"}, "id": "che_0985", "kind": "multiple_choice", "lang": "en", "question": "How is aluminum extracted?", "steps": ["Too reactive for carbon.", "Electric current frees it.", "Select option A."], "subject": "chemistry", "text": "Answer: Electrolysis.\nSteps:\n1. Too reactive for carbon.\n2. Electric current frees it.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "The cell potential is 1.56 V, from 0.80 - (-0.76).", "choices": null, "id": "che_0986", "kind": "worked_example", "lang": "en", "question": "Compute E cell for Zn/Ag with E(Zn) = -0.76 V and E(Ag) = 0.80 V.", "steps": ["Cathode is Ag at 0.80 V.", "Anode is Zn at -0.76 V.", "E = 0.80 - (-0.76) = 1.56 V."], "subject": "chemistry", "text": "Answer: 1.56 V.\nSteps:\n1. Cathode is Ag at 0.80 V.\n2. Anode is Zn at -0.76 V.\n3. E = 0.80 - (-0.76) = 1.56 V.", "topic": "electrochemistry"}
{"answer": "Elektrolyt je látka vedoucí proud pomocí iontů.", "choices": null, "id": "che_0987", "kind": "concept", "lang": "cs", "question": "Co je elektrolyt?", "steps": ["Roztok nebo tavenina.", "Ionty nesou náboj.", "Příklad: NaCl ve vodě."], "subject": "chemistry", "text": "Answer: Vodič proudu ionty.\nSteps:\n1. Roztok nebo tavenina.\n2. Ionty nesou náboj.\n3. Příklad: NaCl ve vodě.", "topic": "electrochemistry"}
{"answer": "Ions migrating through the electrolyte carry the current.", "choices": {"A": "Electrons", "B": "Ions", "C": "Photons", "D": "Neutrons"}, "id": "che_0988", "kind": "multiple_choice", "lang": "en", "question": "How does an electrolyte conduct?", "steps": ["Ions move to electrodes.", "Charge flows with them.", "Select option B."], "subject": "chemistry", "text": "Answer: Ions.\nSteps:\n1. Ions move to electrodes.\n2. Charge flows with them.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "ΔG is -151 kJ, from -1 x 96485 x 1.56 J.", "choices": null, "id": "che_0989", "kind": "worked_example", "lang": "en", "question": "Compute ΔG for n = 1 and E = 1.56 V (F = 96485 C/mol).", "steps": ["Write: ΔG = -1 x 96485 x 1.56.", "Multiply: -150,517 J.", "ΔG = -151 kJ."], "subject": "chemistry", "text": "Answer: -151 kJ.\nSteps:\n1. Write: ΔG = -1 x 96485 x 1.56.\n2. Multiply: -150,517 J.\n3. ΔG = -151 kJ.", "topic": "electrochemistry"}
{"answer": "The potential is 1.53 V, from 1.56 - 0.0296 x log(10).", "choices": null, "id": "che_0990", "kind": "worked_example", "lang": "en", "question": "E° = 1.56 V, n = 2, Q = 10 at 25 C. Compute E.", "steps": ["Write: E = 1.56 - 0.0296 x 1.", "Subtract: 1.56 - 0.0296.", "E = 1.53 V."], "subject": "chemistry", "text": "Answer: 1.53 V.\nSteps:\n1. Write: E = 1.56 - 0.0296 x 1.\n2. Subtract: 1.56 - 0.0296.\n3. E = 1.53 V.", "topic": "electrochemistry"}
{"answer": "More electrons divide the Nernst slope, shrinking the correction.", "choices": {"A": "Bigger", "B": "Zero", "C": "Smaller", "D": "Negative"}, "id": "che_0991", "kind": "multiple_choice", "lang": "en", "question": "How does bigger n change the Nernst correction?", "steps": ["Slope is 0.0592/n.", "Larger n divides more.", "Select option C."], "subject": "chemistry", "text": "Answer: Smaller.\nSteps:\n1. Slope is 0.0592/n.\n2. Larger n divides more.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}
{"answer": "Electroplating coats objects with metal for protection and shine.", "choices": null, "id": "che_0992", "kind": "concept", "lang": "en", "question": "Why is electroplating done?", "steps": ["Metal layer deposits.", "Resists corrosion.", "Looks attractive."], "subject": "chemistry", "text": "Answer: Protection and shine.\nSteps:\n1. Metal layer deposits.\n2. Resists corrosion.\n3. Looks attractive.", "topic": "electrochemistry"}
{"answer": "Vyloučí se 107,87 g stříbra, protože 1 mol elektronů dá 1 mol Ag.", "choices": null, "id": "che_0993", "kind": "worked_example", "lang": "cs", "question": "Kolik stříbra vyloučí 1 mol elektronů (M = 107,87 g/mol)?", "steps": ["1 e- dá 1 Ag.", "Moly Ag = 1.", "Hmotnost = 107,87 g."], "subject": "chemistry", "text": "Answer: 107,87 g.\nSteps:\n1. 1 e- dá 1 Ag.\n2. Moly Ag = 1.\n3. Hmotnost = 107,87 g.", "topic": "electrochemistry"}
{"answer": "One mole of electrons plates one mole of silver at 107.87 g.", "choices": {"A": "53.94 g", "B": "215.74 g", "C": "96.49 g", "D": "107.87 g"}, "id": "che_0994", "kind": "multiple_choice", "lang": "en", "question": "What mass of Ag does 1 mol of electrons plate?", "steps": ["1 e- gives 1 Ag.", "Mass is 107.87 g.", "Select option D."], "subject": "chemistry", "text": "Answer: 107.87 g.\nSteps:\n1. 1 e- gives 1 Ag.\n2. Mass is 107.87 g.\n3. Select option D.\nAnswer: (D)", "topic": "electrochemistry"}
{"answer": "The time is 13.4 h, from 48,243 C divided by 1.00 A.", "choices": null, "id": "che_0995", "kind": "worked_example", "lang": "en", "question": "How long at 1.00 A to pass 0.500 mol of electrons?", "steps": ["Q = 0.500 x 96485 = 48,243 C.", "t = 48,243/1.00 = 48,243 s.", "t = 13.4 h."], "subject": "chemistry", "text": "Answer: 13.4 h.\nSteps:\n1. Q = 0.500 x 96485 = 48,243 C.\n2. t = 48,243/1.00 = 48,243 s.\n3. t = 13.4 h.", "topic": "electrochemistry"}
{"answer": "One ampere is one coulomb per second.", "choices": {"A": "C/s", "B": "J/C", "C": "J/s", "D": "V/m"}, "id": "che_0996", "kind": "multiple_choice", "lang": "en", "question": "What is an ampere?", "steps": ["Current is charge flow.", "Unit is C/s.", "Select option A."], "subject": "chemistry", "text": "Answer: C/s.\nSteps:\n1. Current is charge flow.\n2. Unit is C/s.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "One volt is one joule per coulomb.", "choices": {"A": "C/s", "B": "J/C", "C": "Ohm", "D": "Mol"}, "id": "che_0997", "kind": "multiple_choice", "lang": "en", "question": "What is a volt?", "steps": ["Potential is energy per charge.", "Unit is J/C.", "Select option B."], "subject": "chemistry", "text": "Answer: J/C.\nSteps:\n1. Potential is energy per charge.\n2. Unit is J/C.\n3. Select option B.\nAnswer: (B)", "topic": "electrochemistry"}
{"answer": "Galvanizace je pokovení předmětu zinkem proti korozi.", "choices": null, "id": "che_0998", "kind": "concept", "lang": "cs", "question": "Co je galvanizace?", "steps": ["Zinkový povlak.", "Chrání ocel.", "Obětovaná ochrana."], "subject": "chemistry", "text": "Answer: Pozinkování proti korozi.\nSteps:\n1. Zinkový povlak.\n2. Chrání ocel.\n3. Obětovaná ochrana.", "topic": "electrochemistry"}
{"answer": "Galvanizing coats steel with a protective zinc layer.", "choices": {"A": "Zn", "B": "Cu", "C": "Au", "D": "Fe"}, "id": "che_0999", "kind": "multiple_choice", "lang": "en", "question": "Which metal is used for galvanizing?", "steps": ["Zinc sacrifices itself.", "Coats the steel.", "Select option A."], "subject": "chemistry", "text": "Answer: Zn.\nSteps:\n1. Zinc sacrifices itself.\n2. Coats the steel.\n3. Select option A.\nAnswer: (A)", "topic": "electrochemistry"}
{"answer": "Rust is hydrated iron(III) oxide with formula Fe2O3.xH2O.", "choices": {"A": "FeO", "B": "Fe3O4", "C": "Fe2O3.xH2O", "D": "FeCl3"}, "id": "che_1000", "kind": "multiple_choice", "lang": "en", "question": "What is the formula of rust?", "steps": ["Iron(III) oxide base.", "Water bound in.", "Select option C."], "subject": "chemistry", "text": "Answer: Fe2O3.xH2O.\nSteps:\n1. Iron(III) oxide base.\n2. Water bound in.\n3. Select option C.\nAnswer: (C)", "topic": "electrochemistry"}