Unit 8 — End of Topic Tests (reviewer copy: all keys and model answers visible)

[
 {
  "value": "6:7",
  "misconception": "you reversed the order — the question asks O₂ to H₂O, so O₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order. The question asks O₂ to H₂O, so O₂'s coefficient 7 comes first: 7:6."
 },
 {
  "value": "7:4",
  "misconception": "you took CO₂'s coefficient instead of H₂O's — the second number must belong to the substance named second",
  "feedback": "This answer is wrong — you took CO₂'s coefficient 4 instead of H₂O's. The second number must belong to the substance named second, H₂O, whose coefficient is 6: 7:6."
 },
 {
  "value": "2:6",
  "misconception": "you paired C₂H₆'s coefficient with H₂O — neither substance in the asked pair has the coefficient 2",
  "feedback": "This answer is wrong — you paired C₂H₆'s coefficient 2 with H₂O. Neither substance in the asked pair has the coefficient 2; O₂'s is 7 and H₂O's is 6: 7:6."
 }
]

{
 "keyExplanation": "The coefficient of O₂ is 7, and the coefficient of H₂O is 6. Take the coefficients in the order asked: O₂ first, H₂O second. The mole ratio of O₂ to H₂O is 7:6.",
 "anticipatedWrong": [
  {
   "value": "6:7",
   "misconception": "you reversed the order — the question asks O₂ to H₂O, so O₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order. The question asks O₂ to H₂O, so O₂'s coefficient 7 comes first: 7:6."
  },
  {
   "value": "7:4",
   "misconception": "you took CO₂'s coefficient instead of H₂O's — the second number must belong to the substance named second",
   "feedback": "This answer is wrong — you took CO₂'s coefficient 4 instead of H₂O's. The second number must belong to the substance named second, H₂O, whose coefficient is 6: 7:6."
  },
  {
   "value": "2:6",
   "misconception": "you paired C₂H₆'s coefficient with H₂O — neither substance in the asked pair has the coefficient 2",
   "feedback": "This answer is wrong — you paired C₂H₆'s coefficient 2 with H₂O. Neither substance in the asked pair has the coefficient 2; O₂'s is 7 and H₂O's is 6: 7:6."
  }
 ]
}

[
 {
  "value": 9.0,
  "misconception": "you turned the fraction upside down — the wanted substance Fe's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Fe's coefficient 2 sits on top."
 },
 {
  "value": 6.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of Fe to CO is 2:3",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of Fe to CO is 2:3."
 },
 {
  "value": 12.0,
  "misconception": "you multiplied by Fe's coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by Fe's coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of CO = 6.0 mol\nWrite down the equation:\nmoles of Fe = moles of CO × (coefficient of Fe ÷ coefficient of CO)\nSubstitute in the values, and calculate:\nmoles of Fe = 6.0 × (2 ÷ 3)\nmoles of Fe = 4.0 mol"
}

[
 {
  "value": "2:2",
  "misconception": "you used the subscript 2 inside SnO₂ as its coefficient — SnO₂ has no written coefficient, so its coefficient is 1",
  "feedback": "This answer is wrong — you used the subscript 2 inside SnO₂ as its coefficient — SnO₂ has no written coefficient, so its coefficient is 1."
 },
 {
  "value": "2:1",
  "misconception": "you reversed the order — the question asks SnO₂ to H₂, so SnO₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order — the question asks SnO₂ to H₂, so SnO₂'s coefficient comes first."
 },
 {
  "value": "1:1",
  "misconception": "you took Sn's coefficient for H₂ — the second number must belong to H₂, whose coefficient is 2",
  "feedback": "This answer is wrong — you took Sn's coefficient for H₂ — the second number must belong to H₂, whose coefficient is 2."
 }
]

{
 "keyExplanation": "SnO₂ has no written coefficient, so its coefficient is 1; the coefficient of H₂ is 2. The subscript 2 inside SnO₂ counts atoms in one formula unit and plays no part in the mole ratio. The mole ratio of SnO₂ to H₂ is 1:2.",
 "anticipatedWrong": [
  {
   "value": "2:2",
   "misconception": "you used the subscript 2 inside SnO₂ as its coefficient — SnO₂ has no written coefficient, so its coefficient is 1",
   "feedback": "This answer is wrong — you used the subscript 2 inside SnO₂ as its coefficient — SnO₂ has no written coefficient, so its coefficient is 1."
  },
  {
   "value": "2:1",
   "misconception": "you reversed the order — the question asks SnO₂ to H₂, so SnO₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order — the question asks SnO₂ to H₂, so SnO₂'s coefficient comes first."
  },
  {
   "value": "1:1",
   "misconception": "you took Sn's coefficient for H₂ — the second number must belong to H₂, whose coefficient is 2",
   "feedback": "This answer is wrong — you took Sn's coefficient for H₂ — the second number must belong to H₂, whose coefficient is 2."
  }
 ]
}

[
 {
  "value": 1.0,
  "misconception": "you turned the fraction upside down — the wanted substance O₂'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance O₂'s coefficient 1 sits on top."
 },
 {
  "value": 0.5,
  "misconception": "you skipped the mole-ratio step — 0.50 mol is the Ag₂O's moles, not the O₂'s",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 0.50 mol is the Ag₂O's moles, not the O₂'s."
 },
 {
  "value": 57.95,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Ag₂O = 115.9 g,  M of Ag₂O = 231.8 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Ag₂O = 115.9 / 231.8\nn of Ag₂O = 0.50 mol\nStep 2 — convert to moles of O₂ with the mole ratio:\nmoles of O₂ = moles of Ag₂O × (coefficient of O₂ ÷ coefficient of Ag₂O)\nmoles of O₂ = 0.50 × (1 ÷ 2)\nmoles of O₂ = 0.25 mol"
}

[
 {
  "value": 424.0,
  "misconception": "you skipped the mole-ratio step — 4.0 mol is the NaHCO₃'s moles, and only half as many moles of Na₂CO₃ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 4.0 mol is the NaHCO₃'s moles, and only half as many moles of Na₂CO₃ form."
 },
 {
  "value": 848.0,
  "misconception": "you turned the fraction upside down — the wanted substance Na₂CO₃'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Na₂CO₃'s coefficient 1 sits on top."
 },
 {
  "value": 168.0,
  "misconception": "you used NaHCO₃'s molar mass (84.0 g/mol) — step 2 needs the WANTED substance Na₂CO₃'s molar mass",
  "feedback": "This answer is wrong — you used NaHCO₃'s molar mass (84.0 g/mol) — step 2 needs the WANTED substance Na₂CO₃'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of NaHCO₃ = 4.0 mol,  M of Na₂CO₃ = 106.0 g/mol\nStep 1 — convert to moles of Na₂CO₃ with the mole ratio:\nmoles of Na₂CO₃ = moles of NaHCO₃ × (coefficient of Na₂CO₃ ÷ coefficient of NaHCO₃)\nmoles of Na₂CO₃ = 4.0 × (1 ÷ 2)\nmoles of Na₂CO₃ = 2.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of Na₂CO₃ = 2.0 × 106.0\nm of Na₂CO₃ = 212.0 g"
}

[
 {
  "value": 0.16,
  "misconception": "you turned the fraction upside down — the wanted substance O₂'s coefficient 25 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance O₂'s coefficient 25 sits on top."
 },
 {
  "value": 50.0,
  "misconception": "you forgot C₈H₁₈'s coefficient 2 on the bottom of the fraction",
  "feedback": "This answer is wrong — you forgot C₈H₁₈'s coefficient 2 on the bottom of the fraction."
 },
 {
  "value": 2.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of O₂ to C₈H₁₈ is 25:2",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of O₂ to C₈H₁₈ is 25:2."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of C₈H₁₈ = 2.0 mol\nWrite down the equation:\nmoles of O₂ = moles of C₈H₁₈ × (coefficient of O₂ ÷ coefficient of C₈H₁₈)\nSubstitute in the values, and calculate:\nmoles of O₂ = 2.0 × (25 ÷ 2)\nmoles of O₂ = 25.0 mol"
}

[
 {
  "value": 1308.0,
  "misconception": "you skipped the mole-ratio step — 12.0 mol is the F₂'s moles, not the CrF₃'s",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 12.0 mol is the F₂'s moles, not the CrF₃'s."
 },
 {
  "value": 1962.0,
  "misconception": "you turned the fraction upside down — the wanted substance CrF₃'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance CrF₃'s coefficient 2 sits on top."
 },
 {
  "value": 304.0,
  "misconception": "you used F₂'s molar mass in step 3 — the final step needs the WANTED substance CrF₃'s molar mass",
  "feedback": "This answer is wrong — you used F₂'s molar mass in step 3 — the final step needs the WANTED substance CrF₃'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of F₂ = 456.0 g,  M of F₂ = 38.0 g/mol,  M of CrF₃ = 109.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of F₂ = 456.0 / 38.0\nn of F₂ = 12.0 mol\nStep 2 — convert to moles of CrF₃ with the mole ratio:\nmoles of CrF₃ = moles of F₂ × (coefficient of CrF₃ ÷ coefficient of F₂)\nmoles of CrF₃ = 12.0 × (2 ÷ 3)\nmoles of CrF₃ = 8.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of CrF₃ = 8.0 × 109.0\nm of CrF₃ = 872.0 g"
}

[
 {
  "value": 181.8,
  "misconception": "you ignored the coefficient 2 on V₂O₅ — its mass is 2 × 181.8 g",
  "feedback": "This answer is wrong — you ignored the coefficient 2 on V₂O₅ — its mass is 2 × 181.8 g."
 },
 {
  "value": 909.0,
  "misconception": "you multiplied by 5, the O₂ coefficient, instead of by V₂O₅'s own coefficient 2",
  "feedback": "This answer is wrong — you multiplied by 5, the O₂ coefficient, instead of by V₂O₅'s own coefficient 2."
 },
 {
  "value": 183.8,
  "misconception": "you added the coefficient instead of multiplying by it",
  "feedback": "This answer is wrong — you added the coefficient instead of multiplying by it."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nM of V₂O₅ = 181.8 g/mol, coefficient of V₂O₅ = 2\nWrite down the equation:\nmass of each substance = coefficient × molar mass\nSubstitute in the values, and calculate:\ntotal mass of products = 2 × 181.8\ntotal mass of products = 363.6 g"
}

[
 {
  "value": 1.55,
  "misconception": "you turned the fraction upside down — the wanted substance Cu's coefficient 4 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Cu's coefficient 4 sits on top."
 },
 {
  "value": 3.1,
  "misconception": "you stopped at step 1 — 3.1 mol is the Cu₂O's moles, not the Cu's",
  "feedback": "This answer is wrong — you stopped at step 1 — 3.1 mol is the Cu₂O's moles, not the Cu's."
 },
 {
  "value": 886.6,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Cu₂O = 443.3 g,  M of Cu₂O = 143.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Cu₂O = 443.3 / 143.0\nn of Cu₂O = 3.1 mol\nStep 2 — convert to moles of Cu with the mole ratio:\nmoles of Cu = moles of Cu₂O × (coefficient of Cu ÷ coefficient of Cu₂O)\nmoles of Cu = 3.1 × (4 ÷ 2)\nmoles of Cu = 6.2 mol"
}

[
 {
  "value": 95.0,
  "misconception": "you skipped the mole-ratio step — 2.5 mol is the SbF₃'s moles, and more moles of F₂ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.5 mol is the SbF₃'s moles, and more moles of F₂ are needed."
 },
 {
  "value": 63.3,
  "misconception": "you turned the fraction upside down — the wanted substance F₂'s coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance F₂'s coefficient 3 sits on top."
 },
 {
  "value": 670.5,
  "misconception": "you used SbF₃'s molar mass in step 3 — the final step needs the WANTED substance F₂'s molar mass",
  "feedback": "This answer is wrong — you used SbF₃'s molar mass in step 3 — the final step needs the WANTED substance F₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of SbF₃ = 447.0 g,  M of SbF₃ = 178.8 g/mol,  M of F₂ = 38.0 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of SbF₃ = 447.0 / 178.8\nn of SbF₃ = 2.5 mol\nStep 2 — convert to moles of F₂ with the mole ratio:\nmoles of F₂ = moles of SbF₃ × (coefficient of F₂ ÷ coefficient of SbF₃)\nmoles of F₂ = 2.5 × (3 ÷ 2)\nmoles of F₂ = 3.75 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of F₂ = 3.75 × 38.0\nm of F₂ = 142.5 g"
}

[
 {
  "value": 248.0,
  "misconception": "you skipped the mole-ratio step — 2.0 mol is the PCl₃'s moles, and only a quarter as many moles of P₄ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.0 mol is the PCl₃'s moles, and only a quarter as many moles of P₄ are needed."
 },
 {
  "value": 992.0,
  "misconception": "you turned the fraction upside down — the wanted substance P₄'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance P₄'s coefficient 1 sits on top."
 },
 {
  "value": 68.8,
  "misconception": "you used PCl₃'s molar mass (137.5 g/mol) — step 2 needs the WANTED substance P₄'s molar mass",
  "feedback": "This answer is wrong — you used PCl₃'s molar mass (137.5 g/mol) — step 2 needs the WANTED substance P₄'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of PCl₃ = 2.0 mol,  M of P₄ = 124.0 g/mol\nStep 1 — convert to moles of P₄ with the mole ratio:\nmoles of P₄ = moles of PCl₃ × (coefficient of P₄ ÷ coefficient of PCl₃)\nmoles of P₄ = 2.0 × (1 ÷ 4)\nmoles of P₄ = 0.50 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of P₄ = 0.50 × 124.0\nm of P₄ = 62.0 g"
}

[
 {
  "value": 194.4,
  "misconception": "you skipped the mole-ratio step — 8.0 mol is the Ti's moles, and twice as many moles of Mg are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 8.0 mol is the Ti's moles, and twice as many moles of Mg are needed."
 },
 {
  "value": 97.2,
  "misconception": "you turned the fraction upside down — the wanted substance Mg's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Mg's coefficient 2 sits on top."
 },
 {
  "value": 766.4,
  "misconception": "you used Ti's molar mass in step 3 — the final step needs the WANTED substance Mg's molar mass",
  "feedback": "This answer is wrong — you used Ti's molar mass in step 3 — the final step needs the WANTED substance Mg's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Ti = 383.2 g,  M of Ti = 47.9 g/mol,  M of Mg = 24.3 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of Ti = 383.2 / 47.9\nn of Ti = 8.0 mol\nStep 2 — convert to moles of Mg with the mole ratio:\nmoles of Mg = moles of Ti × (coefficient of Mg ÷ coefficient of Ti)\nmoles of Mg = 8.0 × (2 ÷ 1)\nmoles of Mg = 16.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Mg = 16.0 × 24.3\nm of Mg = 388.8 g"
}

[
 {
  "value": 841.8,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the Si's moles, and only a third as many moles of Si₃N₄ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the Si's moles, and only a third as many moles of Si₃N₄ form."
 },
 {
  "value": 2525.4,
  "misconception": "you turned the fraction upside down — the wanted substance Si₃N₄'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Si₃N₄'s coefficient 1 sits on top."
 },
 {
  "value": 56.2,
  "misconception": "you used Si's molar mass in step 3 — the final step needs the WANTED substance Si₃N₄'s molar mass",
  "feedback": "This answer is wrong — you used Si's molar mass in step 3 — the final step needs the WANTED substance Si₃N₄'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Si = 168.6 g,  M of Si = 28.1 g/mol,  M of Si₃N₄ = 140.3 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Si = 168.6 / 28.1\nn of Si = 6.0 mol\nStep 2 — convert to moles of Si₃N₄ with the mole ratio:\nmoles of Si₃N₄ = moles of Si × (coefficient of Si₃N₄ ÷ coefficient of Si)\nmoles of Si₃N₄ = 6.0 × (1 ÷ 3)\nmoles of Si₃N₄ = 2.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Si₃N₄ = 2.0 × 140.3\nm of Si₃N₄ = 280.6 g"
}

[
 {
  "value": "1:2",
  "misconception": "you reversed the order — the question asks NiO to O₂, so NiO's coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order. The question asks NiO to O₂, so NiO's coefficient 2 comes first: 2:1."
 },
 {
  "value": "2:2",
  "misconception": "you used the subscript 2 inside O₂ as its coefficient — O₂ has no written coefficient, so its coefficient is 1",
  "feedback": "This answer is wrong — you used the subscript 2 inside O₂ as its coefficient. Subscripts play no part; O₂ has no written coefficient, so its coefficient is 1: 2:1."
 },
 {
  "value": "1:1",
  "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, and NiO's is 2",
  "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the coefficients: NiO's is 2 and O₂'s is the unwritten 1, so the ratio is 2:1."
 }
]

{
 "keyExplanation": "The coefficient of NiO is 2, and O₂ has no written coefficient, so its coefficient is 1. Take the coefficients in the order asked: NiO first, O₂ second. The mole ratio of NiO to O₂ is 2:1.",
 "anticipatedWrong": [
  {
   "value": "1:2",
   "misconception": "you reversed the order — the question asks NiO to O₂, so NiO's coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order. The question asks NiO to O₂, so NiO's coefficient 2 comes first: 2:1."
  },
  {
   "value": "2:2",
   "misconception": "you used the subscript 2 inside O₂ as its coefficient — O₂ has no written coefficient, so its coefficient is 1",
   "feedback": "This answer is wrong — you used the subscript 2 inside O₂ as its coefficient. Subscripts play no part; O₂ has no written coefficient, so its coefficient is 1: 2:1."
  },
  {
   "value": "1:1",
   "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, and NiO's is 2",
   "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the coefficients: NiO's is 2 and O₂'s is the unwritten 1, so the ratio is 2:1."
  }
 ]
}

[
 {
  "value": 18.0,
  "misconception": "you turned the fraction upside down — the wanted substance SbCl₃'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance SbCl₃'s coefficient 2 sits on top."
 },
 {
  "value": 12.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of SbCl₃ to Cl₂ is 2:3",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of SbCl₃ to Cl₂ is 2:3."
 },
 {
  "value": 24.0,
  "misconception": "you multiplied by SbCl₃'s coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by SbCl₃'s coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Cl₂ = 12.0 mol\nWrite down the equation:\nmoles of SbCl₃ = moles of Cl₂ × (coefficient of SbCl₃ ÷ coefficient of Cl₂)\nSubstitute in the values, and calculate:\nmoles of SbCl₃ = 12.0 × (2 ÷ 3)\nmoles of SbCl₃ = 8.0 mol"
}

[
 {
  "value": "1:5",
  "misconception": "you reversed the order — the question asks O₂ to C₃H₈, so O₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order — the question asks O₂ to C₃H₈, so O₂'s coefficient comes first."
 },
 {
  "value": "5:3",
  "misconception": "you paired O₂ with CO₂'s coefficient — the asked partner is C₃H₈, whose unwritten coefficient is 1",
  "feedback": "This answer is wrong — you paired O₂ with CO₂'s coefficient — the asked partner is C₃H₈, whose unwritten coefficient is 1."
 },
 {
  "value": "1:1",
  "misconception": "you matched the substances one-for-one and ignored the coefficients — O₂'s coefficient is 5, and C₃H₈'s unwritten coefficient is 1",
  "feedback": "This answer is wrong — you matched the substances one-for-one and ignored the coefficients — O₂'s coefficient is 5, and C₃H₈'s unwritten coefficient is 1."
 }
]

{
 "keyExplanation": "The coefficient of O₂ is 5, and C₃H₈ has no written coefficient, so its coefficient is 1. The subscripts inside the formulas play no part. Take the coefficients in the order asked: O₂ first, C₃H₈ second. The mole ratio of O₂ to C₃H₈ is 5:1.",
 "anticipatedWrong": [
  {
   "value": "1:5",
   "misconception": "you reversed the order — the question asks O₂ to C₃H₈, so O₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order — the question asks O₂ to C₃H₈, so O₂'s coefficient comes first."
  },
  {
   "value": "5:3",
   "misconception": "you paired O₂ with CO₂'s coefficient — the asked partner is C₃H₈, whose unwritten coefficient is 1",
   "feedback": "This answer is wrong — you paired O₂ with CO₂'s coefficient — the asked partner is C₃H₈, whose unwritten coefficient is 1."
  },
  {
   "value": "1:1",
   "misconception": "you matched the substances one-for-one and ignored the coefficients — O₂'s coefficient is 5, and C₃H₈'s unwritten coefficient is 1",
   "feedback": "This answer is wrong — you matched the substances one-for-one and ignored the coefficients — O₂'s coefficient is 5, and C₃H₈'s unwritten coefficient is 1."
  }
 ]
}

[
 {
  "value": 1.25,
  "misconception": "you turned the fraction upside down — the wanted substance LiCl's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance LiCl's coefficient 2 sits on top."
 },
 {
  "value": 2.5,
  "misconception": "you skipped the mole-ratio step — 2.5 mol is the Cl₂'s moles, not the LiCl's",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.5 mol is the Cl₂'s moles, not the LiCl's."
 },
 {
  "value": 355.0,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Cl₂ = 177.5 g,  M of Cl₂ = 71.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Cl₂ = 177.5 / 71.0\nn of Cl₂ = 2.5 mol\nStep 2 — convert to moles of LiCl with the mole ratio:\nmoles of LiCl = moles of Cl₂ × (coefficient of LiCl ÷ coefficient of Cl₂)\nmoles of LiCl = 2.5 × (2 ÷ 1)\nmoles of LiCl = 5.0 mol"
}

[
 {
  "value": 919.8,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the O₂'s moles, and twice as many moles of BaO form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the O₂'s moles, and twice as many moles of BaO form."
 },
 {
  "value": 459.9,
  "misconception": "you turned the fraction upside down — the wanted substance BaO's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance BaO's coefficient 2 sits on top."
 },
 {
  "value": 384.0,
  "misconception": "you used O₂'s molar mass (32.0 g/mol) — step 2 needs the WANTED substance BaO's molar mass",
  "feedback": "This answer is wrong — you used O₂'s molar mass (32.0 g/mol) — step 2 needs the WANTED substance BaO's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of O₂ = 6.0 mol,  M of BaO = 153.3 g/mol\nStep 1 — convert to moles of BaO with the mole ratio:\nmoles of BaO = moles of O₂ × (coefficient of BaO ÷ coefficient of O₂)\nmoles of BaO = 6.0 × (2 ÷ 1)\nmoles of BaO = 12.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of BaO = 12.0 × 153.3\nm of BaO = 1839.6 g"
}

[
 {
  "value": 1.7,
  "misconception": "you turned the fraction upside down — the wanted substance Zn's coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Zn's coefficient 3 sits on top."
 },
 {
  "value": 5.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of Zn to Zn₃N₂ is 3:1",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of Zn to Zn₃N₂ is 3:1."
 },
 {
  "value": 8.0,
  "misconception": "you added the coefficient instead of multiplying by the ratio",
  "feedback": "This answer is wrong — you added the coefficient instead of multiplying by the ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Zn₃N₂ = 5.0 mol\nWrite down the equation:\nmoles of Zn = moles of Zn₃N₂ × (coefficient of Zn ÷ coefficient of Zn₃N₂)\nSubstitute in the values, and calculate:\nmoles of Zn = 5.0 × (3 ÷ 1)\nmoles of Zn = 15.0 mol"
}

[
 {
  "value": 267.6,
  "misconception": "you skipped the mole-ratio step — 2.0 mol is the I₂'s moles, and twice as many moles of LiI form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.0 mol is the I₂'s moles, and twice as many moles of LiI form."
 },
 {
  "value": 133.8,
  "misconception": "you turned the fraction upside down — the wanted substance LiI's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance LiI's coefficient 2 sits on top."
 },
 {
  "value": 1015.2,
  "misconception": "you used I₂'s molar mass in step 3 — the final step needs the WANTED substance LiI's molar mass",
  "feedback": "This answer is wrong — you used I₂'s molar mass in step 3 — the final step needs the WANTED substance LiI's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of I₂ = 507.6 g,  M of I₂ = 253.8 g/mol,  M of LiI = 133.8 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of I₂ = 507.6 / 253.8\nn of I₂ = 2.0 mol\nStep 2 — convert to moles of LiI with the mole ratio:\nmoles of LiI = moles of I₂ × (coefficient of LiI ÷ coefficient of I₂)\nmoles of LiI = 2.0 × (2 ÷ 1)\nmoles of LiI = 4.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of LiI = 4.0 × 133.8\nm of LiI = 535.2 g"
}

[
 {
  "value": 156.7,
  "misconception": "you ignored the coefficient 2 on F₂ — its mass is 2 × 38.0 g",
  "feedback": "This answer is wrong — you ignored the coefficient 2 on F₂ — its mass is 2 × 38.0 g."
 },
 {
  "value": 275.4,
  "misconception": "you put the coefficient 2 on Sn instead of on F₂ — Sn has no written coefficient, so its coefficient is 1",
  "feedback": "This answer is wrong — you put the coefficient 2 on Sn instead of on F₂ — Sn has no written coefficient, so its coefficient is 1."
 },
 {
  "value": 158.7,
  "misconception": "you added the coefficient instead of multiplying by it",
  "feedback": "This answer is wrong — you added the coefficient instead of multiplying by it."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nM of Sn = 118.7 g/mol, M of F₂ = 38.0 g/mol\nWrite down the equation:\nmass of each substance = coefficient × molar mass\nSubstitute in the values, and calculate:\ntotal mass of reactants = 1 × 118.7 + 2 × 38.0\ntotal mass of reactants = 194.7 g"
}

[
 {
  "value": 0.158,
  "misconception": "you turned the fraction upside down — the wanted substance CO₂'s coefficient 12 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance CO₂'s coefficient 12 sits on top."
 },
 {
  "value": 0.95,
  "misconception": "you stopped at step 1 — 0.95 mol is the hexane's moles, not the CO₂'s",
  "feedback": "This answer is wrong — you stopped at step 1 — 0.95 mol is the hexane's moles, not the CO₂'s."
 },
 {
  "value": 11.4,
  "misconception": "you multiplied by CO₂'s coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by CO₂'s coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of C₆H₁₄ = 81.7 g,  M of C₆H₁₄ = 86.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of C₆H₁₄ = 81.7 / 86.0\nn of C₆H₁₄ = 0.95 mol\nStep 2 — convert to moles of CO₂ with the mole ratio:\nmoles of CO₂ = moles of C₆H₁₄ × (coefficient of CO₂ ÷ coefficient of C₆H₁₄)\nmoles of CO₂ = 0.95 × (12 ÷ 2)\nmoles of CO₂ = 5.7 mol"
}

[
 {
  "value": 137.3,
  "misconception": "you skipped the mole-ratio step — 1.0 mol is the Ba₃N₂'s moles, and 3 mol of Ba are needed for each",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 1.0 mol is the Ba₃N₂'s moles, and 3 mol of Ba are needed for each."
 },
 {
  "value": 45.8,
  "misconception": "you turned the fraction upside down — the wanted substance Ba's coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Ba's coefficient 3 sits on top."
 },
 {
  "value": 1319.7,
  "misconception": "you used Ba₃N₂'s molar mass in step 3 — the final step needs the WANTED substance Ba's molar mass",
  "feedback": "This answer is wrong — you used Ba₃N₂'s molar mass in step 3 — the final step needs the WANTED substance Ba's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Ba₃N₂ = 439.9 g,  M of Ba₃N₂ = 439.9 g/mol,  M of Ba = 137.3 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of Ba₃N₂ = 439.9 / 439.9\nn of Ba₃N₂ = 1.0 mol\nStep 2 — convert to moles of Ba with the mole ratio:\nmoles of Ba = moles of Ba₃N₂ × (coefficient of Ba ÷ coefficient of Ba₃N₂)\nmoles of Ba = 1.0 × (3 ÷ 1)\nmoles of Ba = 3.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Ba = 3.0 × 137.3\nm of Ba = 411.9 g"
}

[
 {
  "value": 120.3,
  "misconception": "you skipped the mole-ratio step — 3.0 mol is the Ca₃N₂'s moles, and 3 mol of Ca are needed for each",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 3.0 mol is the Ca₃N₂'s moles, and 3 mol of Ca are needed for each."
 },
 {
  "value": 40.1,
  "misconception": "you turned the fraction upside down — the wanted substance Ca's coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Ca's coefficient 3 sits on top."
 },
 {
  "value": 1334.7,
  "misconception": "you used Ca₃N₂'s molar mass (148.3 g/mol) — step 2 needs the WANTED substance Ca's molar mass",
  "feedback": "This answer is wrong — you used Ca₃N₂'s molar mass (148.3 g/mol) — step 2 needs the WANTED substance Ca's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Ca₃N₂ = 3.0 mol,  M of Ca = 40.1 g/mol\nStep 1 — convert to moles of Ca with the mole ratio:\nmoles of Ca = moles of Ca₃N₂ × (coefficient of Ca ÷ coefficient of Ca₃N₂)\nmoles of Ca = 3.0 × (3 ÷ 1)\nmoles of Ca = 9.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of Ca = 9.0 × 40.1\nm of Ca = 360.9 g"
}

[
 {
  "value": 117.8,
  "misconception": "you skipped the mole-ratio step — 2.0 mol is the Co₃O₄'s moles, and three times as many moles of Co are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.0 mol is the Co₃O₄'s moles, and three times as many moles of Co are needed."
 },
 {
  "value": 235.6,
  "misconception": "you used O₂'s coefficient 2 in the ratio — the wanted substance is Co, whose coefficient is 3",
  "feedback": "This answer is wrong — you used O₂'s coefficient 2 in the ratio — the wanted substance is Co, whose coefficient is 3."
 },
 {
  "value": 1444.2,
  "misconception": "you used Co₃O₄'s molar mass in step 3 — the final step needs the WANTED substance Co's molar mass",
  "feedback": "This answer is wrong — you used Co₃O₄'s molar mass in step 3 — the final step needs the WANTED substance Co's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Co₃O₄ = 481.4 g,  M of Co₃O₄ = 240.7 g/mol,  M of Co = 58.9 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of Co₃O₄ = 481.4 / 240.7\nn of Co₃O₄ = 2.0 mol\nStep 2 — convert to moles of Co with the mole ratio:\nmoles of Co = moles of Co₃O₄ × (coefficient of Co ÷ coefficient of Co₃O₄)\nmoles of Co = 2.0 × (3 ÷ 1)\nmoles of Co = 6.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Co = 6.0 × 58.9\nm of Co = 353.4 g"
}

[
 {
  "value": 509.0,
  "misconception": "you skipped the mole-ratio step — 10.0 mol is the Ca's moles, and fewer moles of V form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 10.0 mol is the Ca's moles, and fewer moles of V form."
 },
 {
  "value": 1272.5,
  "misconception": "you turned the fraction upside down — the wanted substance V's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance V's coefficient 2 sits on top."
 },
 {
  "value": 160.4,
  "misconception": "you used Ca's molar mass in step 3 — the final step needs the WANTED substance V's molar mass",
  "feedback": "This answer is wrong — you used Ca's molar mass in step 3 — the final step needs the WANTED substance V's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Ca = 401.0 g,  M of Ca = 40.1 g/mol,  M of V = 50.9 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Ca = 401.0 / 40.1\nn of Ca = 10.0 mol\nStep 2 — convert to moles of V with the mole ratio:\nmoles of V = moles of Ca × (coefficient of V ÷ coefficient of Ca)\nmoles of V = 10.0 × (2 ÷ 5)\nmoles of V = 4.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of V = 4.0 × 50.9\nm of V = 203.6 g"
}

[
 {
  "value": "3:4",
  "misconception": "you reversed the order — the question asks Al to O₂, so Al's coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order. The question asks Al to O₂, so Al's coefficient 4 comes first: 4:3."
 },
 {
  "value": "4:2",
  "misconception": "you took Al₂O₃'s coefficient for O₂ — the second number must belong to the substance named second",
  "feedback": "This answer is wrong — you took Al₂O₃'s coefficient 2 for O₂. The second number must belong to the substance named second, O₂, whose coefficient is 3: 4:3."
 },
 {
  "value": "1:1",
  "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, 4 for Al and 3 for O₂",
  "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the written coefficients: 4 for Al and 3 for O₂, so the ratio is 4:3."
 }
]

{
 "keyExplanation": "The coefficient of Al is 4, and the coefficient of O₂ is 3. Take the coefficients in the order asked: Al first, O₂ second. The mole ratio of Al to O₂ is 4:3.",
 "anticipatedWrong": [
  {
   "value": "3:4",
   "misconception": "you reversed the order — the question asks Al to O₂, so Al's coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order. The question asks Al to O₂, so Al's coefficient 4 comes first: 4:3."
  },
  {
   "value": "4:2",
   "misconception": "you took Al₂O₃'s coefficient for O₂ — the second number must belong to the substance named second",
   "feedback": "This answer is wrong — you took Al₂O₃'s coefficient 2 for O₂. The second number must belong to the substance named second, O₂, whose coefficient is 3: 4:3."
  },
  {
   "value": "1:1",
   "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, 4 for Al and 3 for O₂",
   "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the written coefficients: 4 for Al and 3 for O₂, so the ratio is 4:3."
  }
 ]
}

[
 {
  "value": 1.0,
  "misconception": "you turned the fraction upside down — the wanted substance CO₂'s coefficient 6 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance CO₂'s coefficient 6 sits on top."
 },
 {
  "value": 3.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of CO₂ to C₃H₆ is 6:2",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of CO₂ to C₃H₆ is 6:2."
 },
 {
  "value": 18.0,
  "misconception": "you multiplied by CO₂'s coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by CO₂'s coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of C₃H₆ = 3.0 mol\nWrite down the equation:\nmoles of CO₂ = moles of C₃H₆ × (coefficient of CO₂ ÷ coefficient of C₃H₆)\nSubstitute in the values, and calculate:\nmoles of CO₂ = 3.0 × (6 ÷ 2)\nmoles of CO₂ = 9.0 mol"
}

[
 {
  "value": "2:6",
  "misconception": "you used the subscript 2 inside N₂ as its coefficient — N₂ has no written coefficient, so its coefficient is 1",
  "feedback": "This answer is wrong — you used the subscript 2 inside N₂ as its coefficient — N₂ has no written coefficient, so its coefficient is 1."
 },
 {
  "value": "6:1",
  "misconception": "you reversed the order — the question asks N₂ to Li, so N₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order — the question asks N₂ to Li, so N₂'s coefficient comes first."
 },
 {
  "value": "1:2",
  "misconception": "you took Li₃N's coefficient for Li — the second number must belong to Li, whose coefficient is 6",
  "feedback": "This answer is wrong — you took Li₃N's coefficient for Li — the second number must belong to Li, whose coefficient is 6."
 }
]

{
 "keyExplanation": "N₂ has no written coefficient, so its coefficient is 1; the coefficient of Li is 6. The subscript 2 inside N₂ counts atoms in one molecule and plays no part in the mole ratio. The mole ratio of N₂ to Li is 1:6.",
 "anticipatedWrong": [
  {
   "value": "2:6",
   "misconception": "you used the subscript 2 inside N₂ as its coefficient — N₂ has no written coefficient, so its coefficient is 1",
   "feedback": "This answer is wrong — you used the subscript 2 inside N₂ as its coefficient — N₂ has no written coefficient, so its coefficient is 1."
  },
  {
   "value": "6:1",
   "misconception": "you reversed the order — the question asks N₂ to Li, so N₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order — the question asks N₂ to Li, so N₂'s coefficient comes first."
  },
  {
   "value": "1:2",
   "misconception": "you took Li₃N's coefficient for Li — the second number must belong to Li, whose coefficient is 6",
   "feedback": "This answer is wrong — you took Li₃N's coefficient for Li — the second number must belong to Li, whose coefficient is 6."
  }
 ]
}

[
 {
  "value": 1.25,
  "misconception": "you turned the fraction upside down — the wanted substance HCl's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance HCl's coefficient 2 sits on top."
 },
 {
  "value": 2.5,
  "misconception": "you skipped the mole-ratio step — 2.5 mol is the Zn's moles, not the HCl's",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.5 mol is the Zn's moles, not the HCl's."
 },
 {
  "value": 327.0,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Zn = 163.5 g,  M of Zn = 65.4 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Zn = 163.5 / 65.4\nn of Zn = 2.5 mol\nStep 2 — convert to moles of HCl with the mole ratio:\nmoles of HCl = moles of Zn × (coefficient of HCl ÷ coefficient of Zn)\nmoles of HCl = 2.5 × (2 ÷ 1)\nmoles of HCl = 5.0 mol"
}

[
 {
  "value": 672.6,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the S's moles, and only half as many moles of TiS₂ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the S's moles, and only half as many moles of TiS₂ form."
 },
 {
  "value": 1345.2,
  "misconception": "you turned the fraction upside down — the wanted substance TiS₂'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance TiS₂'s coefficient 1 sits on top."
 },
 {
  "value": 96.3,
  "misconception": "you used S's molar mass (32.1 g/mol) — step 2 needs the WANTED substance TiS₂'s molar mass",
  "feedback": "This answer is wrong — you used S's molar mass (32.1 g/mol) — step 2 needs the WANTED substance TiS₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of S = 6.0 mol,  M of TiS₂ = 112.1 g/mol\nStep 1 — convert to moles of TiS₂ with the mole ratio:\nmoles of TiS₂ = moles of S × (coefficient of TiS₂ ÷ coefficient of S)\nmoles of TiS₂ = 6.0 × (1 ÷ 2)\nmoles of TiS₂ = 3.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of TiS₂ = 3.0 × 112.1\nm of TiS₂ = 336.3 g"
}

[
 {
  "value": 2.7,
  "misconception": "you turned the fraction upside down — the wanted substance Cl₂'s coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Cl₂'s coefficient 3 sits on top."
 },
 {
  "value": 4.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of Cl₂ to Au is 3:2",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of Cl₂ to Au is 3:2."
 },
 {
  "value": 12.0,
  "misconception": "you forgot Au's coefficient 2 on the bottom of the fraction",
  "feedback": "This answer is wrong — you forgot Au's coefficient 2 on the bottom of the fraction."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Au = 4.0 mol\nWrite down the equation:\nmoles of Cl₂ = moles of Au × (coefficient of Cl₂ ÷ coefficient of Au)\nSubstitute in the values, and calculate:\nmoles of Cl₂ = 4.0 × (3 ÷ 2)\nmoles of Cl₂ = 6.0 mol"
}

[
 {
  "value": 436.2,
  "misconception": "you skipped the mole-ratio step — 1.5 mol is the Sr's moles, and only a third as many moles of Sr₃N₂ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 1.5 mol is the Sr's moles, and only a third as many moles of Sr₃N₂ form."
 },
 {
  "value": 1308.6,
  "misconception": "you turned the fraction upside down — the wanted substance Sr₃N₂'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Sr₃N₂'s coefficient 1 sits on top."
 },
 {
  "value": 43.8,
  "misconception": "you used Sr's molar mass in step 3 — the final step needs the WANTED substance Sr₃N₂'s molar mass",
  "feedback": "This answer is wrong — you used Sr's molar mass in step 3 — the final step needs the WANTED substance Sr₃N₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Sr = 131.4 g,  M of Sr = 87.6 g/mol,  M of Sr₃N₂ = 290.8 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Sr = 131.4 / 87.6\nn of Sr = 1.5 mol\nStep 2 — convert to moles of Sr₃N₂ with the mole ratio:\nmoles of Sr₃N₂ = moles of Sr × (coefficient of Sr₃N₂ ÷ coefficient of Sr)\nmoles of Sr₃N₂ = 1.5 × (1 ÷ 3)\nmoles of Sr₃N₂ = 0.50 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Sr₃N₂ = 0.50 × 290.8\nm of Sr₃N₂ = 145.4 g"
}

[
 {
  "value": 407.7,
  "misconception": "you ignored the coefficient 2 on AlI₃ — its mass is 2 × 407.7 g",
  "feedback": "This answer is wrong — you ignored the coefficient 2 on AlI₃ — its mass is 2 × 407.7 g."
 },
 {
  "value": 1223.1,
  "misconception": "you multiplied by 3, the I₂ coefficient, instead of by AlI₃'s own coefficient 2",
  "feedback": "This answer is wrong — you multiplied by 3, the I₂ coefficient, instead of by AlI₃'s own coefficient 2."
 },
 {
  "value": 409.7,
  "misconception": "you added the coefficient instead of multiplying by it",
  "feedback": "This answer is wrong — you added the coefficient instead of multiplying by it."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nM of AlI₃ = 407.7 g/mol, coefficient of AlI₃ = 2\nWrite down the equation:\nmass of each substance = coefficient × molar mass\nSubstitute in the values, and calculate:\ntotal mass of products = 2 × 407.7\ntotal mass of products = 815.4 g"
}

[
 {
  "value": 0.21,
  "misconception": "you turned the fraction upside down — the wanted substance CO₂'s coefficient 8 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance CO₂'s coefficient 8 sits on top."
 },
 {
  "value": 0.85,
  "misconception": "you stopped at step 1 — 0.85 mol is the butanol's moles, not the CO₂'s",
  "feedback": "This answer is wrong — you stopped at step 1 — 0.85 mol is the butanol's moles, not the CO₂'s."
 },
 {
  "value": 251.6,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of C₄H₉OH = 62.9 g,  M of C₄H₉OH = 74.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of C₄H₉OH = 62.9 / 74.0\nn of C₄H₉OH = 0.85 mol\nStep 2 — convert to moles of CO₂ with the mole ratio:\nmoles of CO₂ = moles of C₄H₉OH × (coefficient of CO₂ ÷ coefficient of C₄H₉OH)\nmoles of CO₂ = 0.85 × (8 ÷ 2)\nmoles of CO₂ = 3.4 mol"
}

[
 {
  "value": 161.8,
  "misconception": "you skipped the mole-ratio step — 2.0 mol is the MnBr₂'s moles, and twice as many moles of HBr are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.0 mol is the MnBr₂'s moles, and twice as many moles of HBr are needed."
 },
 {
  "value": 80.9,
  "misconception": "you turned the fraction upside down — the wanted substance HBr's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance HBr's coefficient 2 sits on top."
 },
 {
  "value": 858.8,
  "misconception": "you used MnBr₂'s molar mass in step 3 — the final step needs the WANTED substance HBr's molar mass",
  "feedback": "This answer is wrong — you used MnBr₂'s molar mass in step 3 — the final step needs the WANTED substance HBr's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of MnBr₂ = 429.4 g,  M of MnBr₂ = 214.7 g/mol,  M of HBr = 80.9 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of MnBr₂ = 429.4 / 214.7\nn of MnBr₂ = 2.0 mol\nStep 2 — convert to moles of HBr with the mole ratio:\nmoles of HBr = moles of MnBr₂ × (coefficient of HBr ÷ coefficient of MnBr₂)\nmoles of HBr = 2.0 × (2 ÷ 1)\nmoles of HBr = 4.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of HBr = 4.0 × 80.9\nm of HBr = 323.6 g"
}

[
 {
  "value": 490.0,
  "misconception": "you skipped the mole-ratio step — 7.0 mol is the CO₂'s moles, and only a fifth as many moles of C₅H₁₀ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 7.0 mol is the CO₂'s moles, and only a fifth as many moles of C₅H₁₀ are needed."
 },
 {
  "value": 2450.0,
  "misconception": "you turned the fraction upside down — the wanted substance C₅H₁₀'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance C₅H₁₀'s coefficient 2 sits on top."
 },
 {
  "value": 61.6,
  "misconception": "you used CO₂'s molar mass (44.0 g/mol) — step 2 needs the WANTED substance C₅H₁₀'s molar mass",
  "feedback": "This answer is wrong — you used CO₂'s molar mass (44.0 g/mol) — step 2 needs the WANTED substance C₅H₁₀'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of CO₂ = 7.0 mol,  M of C₅H₁₀ = 70.0 g/mol\nStep 1 — convert to moles of C₅H₁₀ with the mole ratio:\nmoles of C₅H₁₀ = moles of CO₂ × (coefficient of C₅H₁₀ ÷ coefficient of CO₂)\nmoles of C₅H₁₀ = 7.0 × (2 ÷ 10)\nmoles of C₅H₁₀ = 1.4 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of C₅H₁₀ = 1.4 × 70.0\nm of C₅H₁₀ = 98.0 g"
}

[
 {
  "value": 149.4,
  "misconception": "you skipped the mole-ratio step — 0.90 mol is the PbI₂'s moles, and twice as many moles of KI are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 0.90 mol is the PbI₂'s moles, and twice as many moles of KI are needed."
 },
 {
  "value": 74.7,
  "misconception": "you turned the fraction upside down — the wanted substance KI's coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance KI's coefficient 2 sits on top."
 },
 {
  "value": 829.8,
  "misconception": "you used PbI₂'s molar mass in step 3 — the final step needs the WANTED substance KI's molar mass",
  "feedback": "This answer is wrong — you used PbI₂'s molar mass in step 3 — the final step needs the WANTED substance KI's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of PbI₂ = 414.9 g,  M of PbI₂ = 461.0 g/mol,  M of KI = 166.0 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of PbI₂ = 414.9 / 461.0\nn of PbI₂ = 0.90 mol\nStep 2 — convert to moles of KI with the mole ratio:\nmoles of KI = moles of PbI₂ × (coefficient of KI ÷ coefficient of PbI₂)\nmoles of KI = 0.90 × (2 ÷ 1)\nmoles of KI = 1.8 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of KI = 1.8 × 166.0\nm of KI = 298.8 g"
}

[
 {
  "value": 2058.3,
  "misconception": "you skipped the mole-ratio step — 9.0 mol is the Mn's moles, and only a third as many moles of Mn₃O₄ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 9.0 mol is the Mn's moles, and only a third as many moles of Mn₃O₄ form."
 },
 {
  "value": 6174.9,
  "misconception": "you turned the fraction upside down — the wanted substance Mn₃O₄'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Mn₃O₄'s coefficient 1 sits on top."
 },
 {
  "value": 164.7,
  "misconception": "you used Mn's molar mass in step 3 — the final step needs the WANTED substance Mn₃O₄'s molar mass",
  "feedback": "This answer is wrong — you used Mn's molar mass in step 3 — the final step needs the WANTED substance Mn₃O₄'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Mn = 494.1 g,  M of Mn = 54.9 g/mol,  M of Mn₃O₄ = 228.7 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Mn = 494.1 / 54.9\nn of Mn = 9.0 mol\nStep 2 — convert to moles of Mn₃O₄ with the mole ratio:\nmoles of Mn₃O₄ = moles of Mn × (coefficient of Mn₃O₄ ÷ coefficient of Mn)\nmoles of Mn₃O₄ = 9.0 × (1 ÷ 3)\nmoles of Mn₃O₄ = 3.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Mn₃O₄ = 3.0 × 228.7\nm of Mn₃O₄ = 686.1 g"
}

[
 {
  "value": "4:3",
  "misconception": "you reversed the order — the question asks O₂ to H₂O, so O₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order. The question asks O₂ to H₂O, so O₂'s coefficient 3 comes first: 3:4."
 },
 {
  "value": "3:2",
  "misconception": "you took CO₂'s coefficient instead of H₂O's — the second number must belong to the substance named second",
  "feedback": "This answer is wrong — you took CO₂'s coefficient 2 instead of H₂O's. The second number must belong to the substance named second, H₂O, whose coefficient is 4: 3:4."
 },
 {
  "value": "1:1",
  "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, 3 for O₂ and 4 for H₂O",
  "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the written coefficients: 3 for O₂ and 4 for H₂O, so the ratio is 3:4."
 }
]

{
 "keyExplanation": "The coefficient of O₂ is 3, and the coefficient of H₂O is 4. Take the coefficients in the order asked: O₂ first, H₂O second. The mole ratio of O₂ to H₂O is 3:4.",
 "anticipatedWrong": [
  {
   "value": "4:3",
   "misconception": "you reversed the order — the question asks O₂ to H₂O, so O₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order. The question asks O₂ to H₂O, so O₂'s coefficient 3 comes first: 3:4."
  },
  {
   "value": "3:2",
   "misconception": "you took CO₂'s coefficient instead of H₂O's — the second number must belong to the substance named second",
   "feedback": "This answer is wrong — you took CO₂'s coefficient 2 instead of H₂O's. The second number must belong to the substance named second, H₂O, whose coefficient is 4: 3:4."
  },
  {
   "value": "1:1",
   "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, 3 for O₂ and 4 for H₂O",
   "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the written coefficients: 3 for O₂ and 4 for H₂O, so the ratio is 3:4."
  }
 ]
}

[
 {
  "value": 0.25,
  "misconception": "you turned the fraction upside down — the wanted substance H₂O's coefficient 8 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance H₂O's coefficient 8 sits on top."
 },
 {
  "value": 1.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of H₂O to C₃H₇OH is 8:2",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of H₂O to C₃H₇OH is 8:2."
 },
 {
  "value": 8.0,
  "misconception": "you multiplied by H₂O's coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by H₂O's coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of C₃H₇OH = 1.0 mol\nWrite down the equation:\nmoles of H₂O = moles of C₃H₇OH × (coefficient of H₂O ÷ coefficient of C₃H₇OH)\nSubstitute in the values, and calculate:\nmoles of H₂O = 1.0 × (8 ÷ 2)\nmoles of H₂O = 4.0 mol"
}

[
 {
  "value": "4:5",
  "misconception": "you used the subscript 4 inside P₄ as its coefficient — P₄ has no written coefficient, so its coefficient is 1",
  "feedback": "This answer is wrong — you used the subscript 4 inside P₄ as its coefficient — P₄ has no written coefficient, so its coefficient is 1."
 },
 {
  "value": "5:1",
  "misconception": "you reversed the order — the question asks P₄ to O₂, so P₄'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order — the question asks P₄ to O₂, so P₄'s coefficient comes first."
 },
 {
  "value": "1:1",
  "misconception": "you took P₄O₁₀'s coefficient for O₂ — the second number must belong to O₂, whose coefficient is 5",
  "feedback": "This answer is wrong — you took P₄O₁₀'s coefficient for O₂ — the second number must belong to O₂, whose coefficient is 5."
 }
]

{
 "keyExplanation": "P₄ has no written coefficient, so its coefficient is 1; the coefficient of O₂ is 5. The subscript 4 inside P₄ counts atoms in one molecule and plays no part in the mole ratio. The mole ratio of P₄ to O₂ is 1:5.",
 "anticipatedWrong": [
  {
   "value": "4:5",
   "misconception": "you used the subscript 4 inside P₄ as its coefficient — P₄ has no written coefficient, so its coefficient is 1",
   "feedback": "This answer is wrong — you used the subscript 4 inside P₄ as its coefficient — P₄ has no written coefficient, so its coefficient is 1."
  },
  {
   "value": "5:1",
   "misconception": "you reversed the order — the question asks P₄ to O₂, so P₄'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order — the question asks P₄ to O₂, so P₄'s coefficient comes first."
  },
  {
   "value": "1:1",
   "misconception": "you took P₄O₁₀'s coefficient for O₂ — the second number must belong to O₂, whose coefficient is 5",
   "feedback": "This answer is wrong — you took P₄O₁₀'s coefficient for O₂ — the second number must belong to O₂, whose coefficient is 5."
  }
 ]
}

[
 {
  "value": 1.0,
  "misconception": "you turned the fraction upside down — the wanted substance Br₂'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Br₂'s coefficient 2 sits on top."
 },
 {
  "value": 2.0,
  "misconception": "you skipped the mole-ratio step — 2.0 mol is the Sn's moles, not the Br₂'s",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 2.0 mol is the Sn's moles, not the Br₂'s."
 },
 {
  "value": 474.8,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Sn = 237.4 g,  M of Sn = 118.7 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Sn = 237.4 / 118.7\nn of Sn = 2.0 mol\nStep 2 — convert to moles of Br₂ with the mole ratio:\nmoles of Br₂ = moles of Sn × (coefficient of Br₂ ÷ coefficient of Sn)\nmoles of Br₂ = 2.0 × (2 ÷ 1)\nmoles of Br₂ = 4.0 mol"
}

[
 {
  "value": 1020.6,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the Cl₂'s moles, and only half as many moles of SiCl₄ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the Cl₂'s moles, and only half as many moles of SiCl₄ form."
 },
 {
  "value": 2041.2,
  "misconception": "you turned the fraction upside down — the wanted substance SiCl₄'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance SiCl₄'s coefficient 1 sits on top."
 },
 {
  "value": 213.0,
  "misconception": "you used Cl₂'s molar mass (71.0 g/mol) — step 2 needs the WANTED substance SiCl₄'s molar mass",
  "feedback": "This answer is wrong — you used Cl₂'s molar mass (71.0 g/mol) — step 2 needs the WANTED substance SiCl₄'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Cl₂ = 6.0 mol,  M of SiCl₄ = 170.1 g/mol\nStep 1 — convert to moles of SiCl₄ with the mole ratio:\nmoles of SiCl₄ = moles of Cl₂ × (coefficient of SiCl₄ ÷ coefficient of Cl₂)\nmoles of SiCl₄ = 6.0 × (1 ÷ 2)\nmoles of SiCl₄ = 3.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of SiCl₄ = 3.0 × 170.1\nm of SiCl₄ = 510.3 g"
}

[
 {
  "value": 0.8,
  "misconception": "you turned the fraction upside down — the wanted substance O₂'s coefficient 4 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance O₂'s coefficient 4 sits on top."
 },
 {
  "value": 3.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of O₂ to C₃H₆O is 4:1",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of O₂ to C₃H₆O is 4:1."
 },
 {
  "value": 9.0,
  "misconception": "you used CO₂'s coefficient — the wanted substance is O₂, whose coefficient is 4",
  "feedback": "This answer is wrong — you used CO₂'s coefficient — the wanted substance is O₂, whose coefficient is 4."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of C₃H₆O = 3.0 mol\nWrite down the equation:\nmoles of O₂ = moles of C₃H₆O × (coefficient of O₂ ÷ coefficient of C₃H₆O)\nSubstitute in the values, and calculate:\nmoles of O₂ = 3.0 × (4 ÷ 1)\nmoles of O₂ = 12.0 mol"
}

[
 {
  "value": 631.2,
  "misconception": "you skipped the mole-ratio step — 4.0 mol is the Mn's moles, and only half as many moles of Mn₂O₃ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 4.0 mol is the Mn's moles, and only half as many moles of Mn₂O₃ form."
 },
 {
  "value": 1262.4,
  "misconception": "you turned the fraction upside down — the wanted substance Mn₂O₃'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Mn₂O₃'s coefficient 2 sits on top."
 },
 {
  "value": 109.8,
  "misconception": "you used Mn's molar mass in step 3 — the final step needs the WANTED substance Mn₂O₃'s molar mass",
  "feedback": "This answer is wrong — you used Mn's molar mass in step 3 — the final step needs the WANTED substance Mn₂O₃'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Mn = 219.6 g,  M of Mn = 54.9 g/mol,  M of Mn₂O₃ = 157.8 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Mn = 219.6 / 54.9\nn of Mn = 4.0 mol\nStep 2 — convert to moles of Mn₂O₃ with the mole ratio:\nmoles of Mn₂O₃ = moles of Mn × (coefficient of Mn₂O₃ ÷ coefficient of Mn)\nmoles of Mn₂O₃ = 4.0 × (2 ÷ 4)\nmoles of Mn₂O₃ = 2.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Mn₂O₃ = 2.0 × 157.8\nm of Mn₂O₃ = 315.6 g"
}

[
 {
  "value": 315.5,
  "misconception": "you ignored the coefficient 2 on BiCl₃ — its mass is 2 × 315.5 g",
  "feedback": "This answer is wrong — you ignored the coefficient 2 on BiCl₃ — its mass is 2 × 315.5 g."
 },
 {
  "value": 946.5,
  "misconception": "you multiplied by 3, the Cl₂ coefficient, instead of by BiCl₃'s own coefficient 2",
  "feedback": "This answer is wrong — you multiplied by 3, the Cl₂ coefficient, instead of by BiCl₃'s own coefficient 2."
 },
 {
  "value": 317.5,
  "misconception": "you added the coefficient instead of multiplying by it",
  "feedback": "This answer is wrong — you added the coefficient instead of multiplying by it."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nM of BiCl₃ = 315.5 g/mol, coefficient of BiCl₃ = 2\nWrite down the equation:\nmass of each substance = coefficient × molar mass\nSubstitute in the values, and calculate:\ntotal mass of products = 2 × 315.5\ntotal mass of products = 631.0 g"
}

[
 {
  "value": 26.0,
  "misconception": "you turned the fraction upside down — the wanted substance N₂'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance N₂'s coefficient 1 sits on top."
 },
 {
  "value": 13.0,
  "misconception": "you stopped at step 1 — 13.0 mol is the AlN's moles, not the N₂'s",
  "feedback": "This answer is wrong — you stopped at step 1 — 13.0 mol is the AlN's moles, not the N₂'s."
 },
 {
  "value": 266.5,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of AlN = 533.0 g,  M of AlN = 41.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of AlN = 533.0 / 41.0\nn of AlN = 13.0 mol\nStep 2 — convert to moles of N₂ with the mole ratio:\nmoles of N₂ = moles of AlN × (coefficient of N₂ ÷ coefficient of AlN)\nmoles of N₂ = 13.0 × (1 ÷ 2)\nmoles of N₂ = 6.5 mol"
}

[
 {
  "value": 156.8,
  "misconception": "you skipped the mole-ratio step — 0.75 mol is the Bi₂O₃'s moles, and twice as many moles of Bi are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 0.75 mol is the Bi₂O₃'s moles, and twice as many moles of Bi are needed."
 },
 {
  "value": 78.4,
  "misconception": "you turned the fraction upside down — the wanted substance Bi's coefficient 4 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Bi's coefficient 4 sits on top."
 },
 {
  "value": 699.0,
  "misconception": "you used Bi₂O₃'s molar mass in step 3 — the final step needs the WANTED substance Bi's molar mass",
  "feedback": "This answer is wrong — you used Bi₂O₃'s molar mass in step 3 — the final step needs the WANTED substance Bi's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Bi₂O₃ = 349.5 g,  M of Bi₂O₃ = 466.0 g/mol,  M of Bi = 209.0 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of Bi₂O₃ = 349.5 / 466.0\nn of Bi₂O₃ = 0.75 mol\nStep 2 — convert to moles of Bi with the mole ratio:\nmoles of Bi = moles of Bi₂O₃ × (coefficient of Bi ÷ coefficient of Bi₂O₃)\nmoles of Bi = 0.75 × (4 ÷ 2)\nmoles of Bi = 1.5 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Bi = 1.5 × 209.0\nm of Bi = 313.5 g"
}

[
 {
  "value": 1278.4,
  "misconception": "you skipped the mole-ratio step — 8.0 mol is the VBr₃'s moles, and more moles of Br₂ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 8.0 mol is the VBr₃'s moles, and more moles of Br₂ are needed."
 },
 {
  "value": 852.3,
  "misconception": "you turned the fraction upside down — the wanted substance Br₂'s coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Br₂'s coefficient 3 sits on top."
 },
 {
  "value": 3487.2,
  "misconception": "you used VBr₃'s molar mass (290.6 g/mol) — step 2 needs the WANTED substance Br₂'s molar mass",
  "feedback": "This answer is wrong — you used VBr₃'s molar mass (290.6 g/mol) — step 2 needs the WANTED substance Br₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of VBr₃ = 8.0 mol,  M of Br₂ = 159.8 g/mol\nStep 1 — convert to moles of Br₂ with the mole ratio:\nmoles of Br₂ = moles of VBr₃ × (coefficient of Br₂ ÷ coefficient of VBr₃)\nmoles of Br₂ = 8.0 × (3 ÷ 2)\nmoles of Br₂ = 12.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of Br₂ = 12.0 × 159.8\nm of Br₂ = 1917.6 g"
}

[
 {
  "value": 114.0,
  "misconception": "you skipped the mole-ratio step — 3.0 mol is the WF₆'s moles, and three times as many moles of F₂ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 3.0 mol is the WF₆'s moles, and three times as many moles of F₂ are needed."
 },
 {
  "value": 38.0,
  "misconception": "you turned the fraction upside down — the wanted substance F₂'s coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance F₂'s coefficient 3 sits on top."
 },
 {
  "value": 2680.2,
  "misconception": "you used WF₆'s molar mass in step 3 — the final step needs the WANTED substance F₂'s molar mass",
  "feedback": "This answer is wrong — you used WF₆'s molar mass in step 3 — the final step needs the WANTED substance F₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of WF₆ = 893.4 g,  M of WF₆ = 297.8 g/mol,  M of F₂ = 38.0 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of WF₆ = 893.4 / 297.8\nn of WF₆ = 3.0 mol\nStep 2 — convert to moles of F₂ with the mole ratio:\nmoles of F₂ = moles of WF₆ × (coefficient of F₂ ÷ coefficient of WF₆)\nmoles of F₂ = 3.0 × (3 ÷ 1)\nmoles of F₂ = 9.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of F₂ = 9.0 × 38.0\nm of F₂ = 342.0 g"
}

[
 {
  "value": 1602.4,
  "misconception": "you skipped the mole-ratio step — 8.0 mol is the Cr's moles, and only half as many moles of Cr₂S₃ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 8.0 mol is the Cr's moles, and only half as many moles of Cr₂S₃ form."
 },
 {
  "value": 3204.8,
  "misconception": "you turned the fraction upside down — the wanted substance Cr₂S₃'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Cr₂S₃'s coefficient 1 sits on top."
 },
 {
  "value": 208.0,
  "misconception": "you used Cr's molar mass in step 3 — the final step needs the WANTED substance Cr₂S₃'s molar mass",
  "feedback": "This answer is wrong — you used Cr's molar mass in step 3 — the final step needs the WANTED substance Cr₂S₃'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Cr = 416.0 g,  M of Cr = 52.0 g/mol,  M of Cr₂S₃ = 200.3 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Cr = 416.0 / 52.0\nn of Cr = 8.0 mol\nStep 2 — convert to moles of Cr₂S₃ with the mole ratio:\nmoles of Cr₂S₃ = moles of Cr × (coefficient of Cr₂S₃ ÷ coefficient of Cr)\nmoles of Cr₂S₃ = 8.0 × (1 ÷ 2)\nmoles of Cr₂S₃ = 4.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Cr₂S₃ = 4.0 × 200.3\nm of Cr₂S₃ = 801.2 g"
}

[
 {
  "value": "2:3",
  "misconception": "you reversed the order — the question asks Cl₂ to Fe, so Cl₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order. The question asks Cl₂ to Fe, so Cl₂'s coefficient 3 comes first: 3:2."
 },
 {
  "value": "3:1",
  "misconception": "you read the subscripts inside FeCl₃ — the 3 Cl and 1 Fe count atoms in one formula unit, not moles in the ratio",
  "feedback": "This answer is wrong — you read the subscripts inside FeCl₃, which count atoms in one formula unit. The mole ratio comes from the written coefficients: 3 for Cl₂ and 2 for Fe, so the ratio is 3:2."
 },
 {
  "value": "1:1",
  "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, 3 for Cl₂ and 2 for Fe",
  "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the written coefficients: 3 for Cl₂ and 2 for Fe, so the ratio is 3:2."
 }
]

{
 "keyExplanation": "The coefficient of Cl₂ is 3, and the coefficient of Fe is 2. Take the coefficients in the order asked: Cl₂ first, Fe second. The subscripts inside FeCl₃ play no part. The mole ratio of Cl₂ to Fe is 3:2.",
 "anticipatedWrong": [
  {
   "value": "2:3",
   "misconception": "you reversed the order — the question asks Cl₂ to Fe, so Cl₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order. The question asks Cl₂ to Fe, so Cl₂'s coefficient 3 comes first: 3:2."
  },
  {
   "value": "3:1",
   "misconception": "you read the subscripts inside FeCl₃ — the 3 Cl and 1 Fe count atoms in one formula unit, not moles in the ratio",
   "feedback": "This answer is wrong — you read the subscripts inside FeCl₃, which count atoms in one formula unit. The mole ratio comes from the written coefficients: 3 for Cl₂ and 2 for Fe, so the ratio is 3:2."
  },
  {
   "value": "1:1",
   "misconception": "you ignored the coefficients — the mole ratio is read from the written coefficients, 3 for Cl₂ and 2 for Fe",
   "feedback": "This answer is wrong — you ignored the coefficients. The mole ratio comes from the written coefficients: 3 for Cl₂ and 2 for Fe, so the ratio is 3:2."
  }
 ]
}

[
 {
  "value": 17.3,
  "misconception": "you turned the fraction upside down — the wanted substance CO₂'s coefficient 7 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance CO₂'s coefficient 7 sits on top."
 },
 {
  "value": 11.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of CO₂ to O₂ is 7:11",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of CO₂ to O₂ is 7:11."
 },
 {
  "value": 77.0,
  "misconception": "you multiplied by CO₂'s coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by CO₂'s coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of O₂ = 11.0 mol\nWrite down the equation:\nmoles of CO₂ = moles of O₂ × (coefficient of CO₂ ÷ coefficient of O₂)\nSubstitute in the values, and calculate:\nmoles of CO₂ = 11.0 × (7 ÷ 11)\nmoles of CO₂ = 7.0 mol"
}

[
 {
  "value": "3:3",
  "misconception": "you used the subscript 3 inside Ca₃P₂ as its coefficient — Ca₃P₂ has no written coefficient, so its coefficient is 1",
  "feedback": "This answer is wrong — you used the subscript 3 inside Ca₃P₂ as its coefficient — Ca₃P₂ has no written coefficient, so its coefficient is 1."
 },
 {
  "value": "3:1",
  "misconception": "you reversed the order — the question asks Ca₃P₂ to Ca, so Ca₃P₂'s coefficient comes first",
  "feedback": "This answer is wrong — you reversed the order — the question asks Ca₃P₂ to Ca, so Ca₃P₂'s coefficient comes first."
 },
 {
  "value": "1:2",
  "misconception": "you took P's coefficient for Ca — the second number must belong to Ca, whose coefficient is 3",
  "feedback": "This answer is wrong — you took P's coefficient for Ca — the second number must belong to Ca, whose coefficient is 3."
 }
]

{
 "keyExplanation": "Ca₃P₂ has no written coefficient, so its coefficient is 1; the coefficient of Ca is 3. The subscript 3 inside Ca₃P₂ counts atoms in one formula unit and plays no part in the mole ratio. The mole ratio of Ca₃P₂ to Ca is 1:3.",
 "anticipatedWrong": [
  {
   "value": "3:3",
   "misconception": "you used the subscript 3 inside Ca₃P₂ as its coefficient — Ca₃P₂ has no written coefficient, so its coefficient is 1",
   "feedback": "This answer is wrong — you used the subscript 3 inside Ca₃P₂ as its coefficient — Ca₃P₂ has no written coefficient, so its coefficient is 1."
  },
  {
   "value": "3:1",
   "misconception": "you reversed the order — the question asks Ca₃P₂ to Ca, so Ca₃P₂'s coefficient comes first",
   "feedback": "This answer is wrong — you reversed the order — the question asks Ca₃P₂ to Ca, so Ca₃P₂'s coefficient comes first."
  },
  {
   "value": "1:2",
   "misconception": "you took P's coefficient for Ca — the second number must belong to Ca, whose coefficient is 3",
   "feedback": "This answer is wrong — you took P's coefficient for Ca — the second number must belong to Ca, whose coefficient is 3."
  }
 ]
}

[
 {
  "value": 3.0,
  "misconception": "you turned the fraction upside down — the wanted substance O₂'s coefficient 1 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance O₂'s coefficient 1 sits on top."
 },
 {
  "value": 1.5,
  "misconception": "you skipped the mole-ratio step — 1.5 mol is the HgO's moles, not the O₂'s",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 1.5 mol is the HgO's moles, not the O₂'s."
 },
 {
  "value": 162.45,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of HgO = 324.9 g,  M of HgO = 216.6 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of HgO = 324.9 / 216.6\nn of HgO = 1.5 mol\nStep 2 — convert to moles of O₂ with the mole ratio:\nmoles of O₂ = moles of HgO × (coefficient of O₂ ÷ coefficient of HgO)\nmoles of O₂ = 1.5 × (1 ÷ 2)\nmoles of O₂ = 0.75 mol"
}

[
 {
  "value": 1624.2,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the Br₂'s moles, not the PBr₃'s",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the Br₂'s moles, not the PBr₃'s."
 },
 {
  "value": 2436.3,
  "misconception": "you turned the fraction upside down — the wanted substance PBr₃'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance PBr₃'s coefficient 2 sits on top."
 },
 {
  "value": 639.2,
  "misconception": "you used Br₂'s molar mass (159.8 g/mol) — step 2 needs the WANTED substance PBr₃'s molar mass",
  "feedback": "This answer is wrong — you used Br₂'s molar mass (159.8 g/mol) — step 2 needs the WANTED substance PBr₃'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Br₂ = 6.0 mol,  M of PBr₃ = 270.7 g/mol\nStep 1 — convert to moles of PBr₃ with the mole ratio:\nmoles of PBr₃ = moles of Br₂ × (coefficient of PBr₃ ÷ coefficient of Br₂)\nmoles of PBr₃ = 6.0 × (2 ÷ 3)\nmoles of PBr₃ = 4.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of PBr₃ = 4.0 × 270.7\nm of PBr₃ = 1082.8 g"
}

[
 {
  "value": 1.3333,
  "misconception": "you turned the fraction upside down — the wanted substance O₂'s coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance O₂'s coefficient 3 sits on top."
 },
 {
  "value": 2.0,
  "misconception": "you ignored the coefficients and matched the moles one-for-one — the ratio of O₂ to W is 3:2",
  "feedback": "This answer is wrong — you ignored the coefficients and matched the moles one-for-one — the ratio of O₂ to W is 3:2."
 },
 {
  "value": 6.0,
  "misconception": "you multiplied by O₂'s coefficient alone instead of the coefficient ratio",
  "feedback": "This answer is wrong — you multiplied by O₂'s coefficient alone instead of the coefficient ratio."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of W = 2.0 mol\nWrite down the equation:\nmoles of O₂ = moles of W × (coefficient of O₂ ÷ coefficient of W)\nSubstitute in the values, and calculate:\nmoles of O₂ = 2.0 × (3 ÷ 2)\nmoles of O₂ = 3.0 mol"
}

[
 {
  "value": 1749.6,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the Sb's moles, and only half as many moles of Sb₂O₃ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the Sb's moles, and only half as many moles of Sb₂O₃ form."
 },
 {
  "value": 3499.2,
  "misconception": "you turned the fraction upside down — the wanted substance Sb₂O₃'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Sb₂O₃'s coefficient 2 sits on top."
 },
 {
  "value": 365.4,
  "misconception": "you used Sb's molar mass in step 3 — the final step needs the WANTED substance Sb₂O₃'s molar mass",
  "feedback": "This answer is wrong — you used Sb's molar mass in step 3 — the final step needs the WANTED substance Sb₂O₃'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Sb = 730.8 g,  M of Sb = 121.8 g/mol,  M of Sb₂O₃ = 291.6 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Sb = 730.8 / 121.8\nn of Sb = 6.0 mol\nStep 2 — convert to moles of Sb₂O₃ with the mole ratio:\nmoles of Sb₂O₃ = moles of Sb × (coefficient of Sb₂O₃ ÷ coefficient of Sb)\nmoles of Sb₂O₃ = 6.0 × (2 ÷ 4)\nmoles of Sb₂O₃ = 3.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Sb₂O₃ = 3.0 × 291.6\nm of Sb₂O₃ = 874.8 g"
}

[
 {
  "value": 178.9,
  "misconception": "you ignored both coefficients — each substance's mass is its coefficient multiplied by its molar mass",
  "feedback": "This answer is wrong — you ignored both coefficients — each substance's mass is its coefficient multiplied by its molar mass."
 },
 {
  "value": 249.9,
  "misconception": "you swapped the coefficients — the 2 belongs to Ag and the unwritten 1 belongs to Cl₂",
  "feedback": "This answer is wrong — you swapped the coefficients — the 2 belongs to Ag and the unwritten 1 belongs to Cl₂."
 },
 {
  "value": 181.9,
  "misconception": "you added each coefficient instead of multiplying by it",
  "feedback": "This answer is wrong — you added each coefficient instead of multiplying by it."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nM of Ag = 107.9 g/mol, M of Cl₂ = 71.0 g/mol\nWrite down the equation:\nmass of each substance = coefficient × molar mass\nSubstitute in the values, and calculate:\ntotal mass of reactants = 2 × 107.9 + 1 × 71.0\ntotal mass of reactants = 286.8 g"
}

[
 {
  "value": 0.092,
  "misconception": "you turned the fraction upside down — the wanted substance CO₂'s coefficient 6 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance CO₂'s coefficient 6 sits on top."
 },
 {
  "value": 0.55,
  "misconception": "you stopped at step 1 — 0.55 mol is the glucose's moles, not the CO₂'s",
  "feedback": "This answer is wrong — you stopped at step 1 — 0.55 mol is the glucose's moles, not the CO₂'s."
 },
 {
  "value": 594.0,
  "misconception": "you applied the mole ratio to the mass instead of converting to moles first",
  "feedback": "This answer is wrong — you applied the mole ratio to the mass instead of converting to moles first."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of C₆H₁₂O₆ = 99.0 g,  M of C₆H₁₂O₆ = 180.0 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of C₆H₁₂O₆ = 99.0 / 180.0\nn of C₆H₁₂O₆ = 0.55 mol\nStep 2 — convert to moles of CO₂ with the mole ratio:\nmoles of CO₂ = moles of C₆H₁₂O₆ × (coefficient of CO₂ ÷ coefficient of C₆H₁₂O₆)\nmoles of CO₂ = 0.55 × (6 ÷ 1)\nmoles of CO₂ = 3.3 mol"
}

[
 {
  "value": 178.2,
  "misconception": "you skipped the mole-ratio step — 3.5 mol is the V₂O₃'s moles, and twice as many moles of V are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 3.5 mol is the V₂O₃'s moles, and twice as many moles of V are needed."
 },
 {
  "value": 89.1,
  "misconception": "you turned the fraction upside down — the wanted substance V's coefficient 4 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance V's coefficient 4 sits on top."
 },
 {
  "value": 1048.6,
  "misconception": "you used V₂O₃'s molar mass in step 3 — the final step needs the WANTED substance V's molar mass",
  "feedback": "This answer is wrong — you used V₂O₃'s molar mass in step 3 — the final step needs the WANTED substance V's molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of V₂O₃ = 524.3 g,  M of V₂O₃ = 149.8 g/mol,  M of V = 50.9 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of V₂O₃ = 524.3 / 149.8\nn of V₂O₃ = 3.5 mol\nStep 2 — convert to moles of V with the mole ratio:\nmoles of V = moles of V₂O₃ × (coefficient of V ÷ coefficient of V₂O₃)\nmoles of V = 3.5 × (4 ÷ 2)\nmoles of V = 7.0 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of V = 7.0 × 50.9\nm of V = 356.3 g"
}

[
 {
  "value": 1196.0,
  "misconception": "you skipped the mole-ratio step — 5.0 mol is the O₂'s moles, and twice as many moles of PbO₂ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 5.0 mol is the O₂'s moles, and twice as many moles of PbO₂ are needed."
 },
 {
  "value": 598.0,
  "misconception": "you turned the fraction upside down — the wanted substance PbO₂'s coefficient 2 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance PbO₂'s coefficient 2 sits on top."
 },
 {
  "value": 320.0,
  "misconception": "you used O₂'s molar mass (32.0 g/mol) — step 2 needs the WANTED substance PbO₂'s molar mass",
  "feedback": "This answer is wrong — you used O₂'s molar mass (32.0 g/mol) — step 2 needs the WANTED substance PbO₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of O₂ = 5.0 mol,  M of PbO₂ = 239.2 g/mol\nStep 1 — convert to moles of PbO₂ with the mole ratio:\nmoles of PbO₂ = moles of O₂ × (coefficient of PbO₂ ÷ coefficient of O₂)\nmoles of PbO₂ = 5.0 × (2 ÷ 1)\nmoles of PbO₂ = 10.0 mol\nStep 2 — convert the moles to mass:\nm = n × M\nm of PbO₂ = 10.0 × 239.2\nm of PbO₂ = 2392.0 g"
}

[
 {
  "value": 479.4,
  "misconception": "you skipped the mole-ratio step — 3.0 mol is the CrBr₃'s moles, and half as many again moles of Br₂ are needed",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 3.0 mol is the CrBr₃'s moles, and half as many again moles of Br₂ are needed."
 },
 {
  "value": 319.6,
  "misconception": "you turned the fraction upside down — the wanted substance Br₂'s coefficient 3 sits on top",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Br₂'s coefficient 3 sits on top."
 },
 {
  "value": 1312.7,
  "misconception": "you used CrBr₃'s molar mass in step 3 — the final step needs the WANTED substance Br₂'s molar mass",
  "feedback": "This answer is wrong — you used CrBr₃'s molar mass in step 3 — the final step needs the WANTED substance Br₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of CrBr₃ = 875.1 g,  M of CrBr₃ = 291.7 g/mol,  M of Br₂ = 159.8 g/mol\nStep 1 — convert the target mass to moles:\nn = m / M\nn of CrBr₃ = 875.1 / 291.7\nn of CrBr₃ = 3.0 mol\nStep 2 — convert to moles of Br₂ with the mole ratio:\nmoles of Br₂ = moles of CrBr₃ × (coefficient of Br₂ ÷ coefficient of CrBr₃)\nmoles of Br₂ = 3.0 × (3 ÷ 2)\nmoles of Br₂ = 4.5 mol\nStep 3 — convert the moles to mass:\nm = n × M\nm of Br₂ = 4.5 × 159.8\nm of Br₂ = 719.1 g"
}

[
 {
  "value": 605.4,
  "misconception": "you skipped the mole-ratio step — 6.0 mol is the Mg's moles; only a third as many moles of Mg₃N₂ form",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 6.0 mol is the Mg's moles; only a third as many moles of Mg₃N₂ form."
 },
 {
  "value": 1816.2,
  "misconception": "you turned the fraction upside down — the wanted substance Mg₃N₂'s coefficient 1 sits on top, over Mg's 3",
  "feedback": "This answer is wrong — you turned the fraction upside down — the wanted substance Mg₃N₂'s coefficient 1 sits on top, over Mg's 3."
 },
 {
  "value": 48.6,
  "misconception": "you used Mg's molar mass in step 3 — the final step needs the WANTED substance Mg₃N₂'s molar mass",
  "feedback": "This answer is wrong — you used Mg's molar mass in step 3 — the final step needs the WANTED substance Mg₃N₂'s molar mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Mg = 145.8 g,  M of Mg = 24.3 g/mol,  M of Mg₃N₂ = 100.9 g/mol\nStep 1 — convert the mass to moles:\nn = m / M\nn of Mg = 145.8 / 24.3\nn of Mg = 6.0 mol\nStep 2 — convert to moles of Mg₃N₂ with the mole ratio:\nmoles of Mg₃N₂ = moles of Mg × (coefficient of Mg₃N₂ ÷ coefficient of Mg)\nmoles of Mg₃N₂ = 6.0 × (1 ÷ 3)\nmoles of Mg₃N₂ = 2.0 mol\nStep 3 — convert the moles to a mass with the WANTED substance's molar mass:\nm = n × M\nm of Mg₃N₂ = 2.0 × 100.9\nm of Mg₃N₂ = 201.8 g"
}

[
 {
  "value": 10.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 },
 {
  "value": 12.0,
  "misconception": "you started from the excess reactant C₃H₈ — the limiting reactant O₂ caps the product",
  "feedback": null
 },
 {
  "value": 16.7,
  "misconception": "you flipped the mole ratio — the coefficient of CO₂ goes on top and O₂'s underneath",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of O₂ (limiting) = 10.0 mol\nThe 4.0 mol of C₃H₈ is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of CO₂ = moles of O₂ × (coefficient of CO₂ ÷ coefficient of O₂)\nSubstitute in the values, and calculate:\nmoles of CO₂ = 10.0 × (3 ÷ 5)\nmoles of CO₂ = 6.0 mol"
}

[
 {
  "value": 6.0,
  "misconception": "you started from the excess reactant Cu — once the 1.0 mol of O₂ is used up, no more CuO can form no matter how much Cu remains",
  "feedback": null
 },
 {
  "value": 12.0,
  "misconception": "you multiplied the excess reactant's moles by the ratio — the calculation must start from the limiting reactant O₂",
  "feedback": null
 },
 {
  "value": 0.5,
  "misconception": "you flipped the mole ratio — the coefficient of CuO goes on top and O₂'s underneath",
  "feedback": null
 }
]

{
 "keyExplanation": "Product can only form while every reactant is still available, so the reactant that runs out first stops product formation. O₂ is limiting, so the calculation starts from its 1.0 mol.\nWrite down the values in the question:\nmoles of O₂ (limiting) = 1.0 mol\nThe 6.0 mol of Cu is the excess reactant — it does not enter the calculation, and most of it is left over when the reaction stops.\nWrite down the equation:\nmoles of CuO = moles of O₂ × (coefficient of CuO ÷ coefficient of O₂)\nSubstitute in the values, and calculate:\nmoles of CuO = 1.0 × (2 ÷ 1)\nmoles of CuO = 2.0 mol"
}

[
 {
  "value": 63.4,
  "misconception": "you calculated from the excess reactant Fe — using up 0.50 mol of Fe would need 1.0 mol of HCl, and only 0.8000 mol is available, so HCl is limiting",
  "feedback": null
 },
 {
  "value": 57.1,
  "misconception": "you added the two reactant masses — the leftover excess iron is not part of the product",
  "feedback": null
 },
 {
  "value": 101.44,
  "misconception": "you skipped the mole-ratio step — 0.80 mol is the HCl's moles, and every 2 mol of HCl makes only 1 mol of FeCl₂",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Fe = 27.9 g,  M of Fe = 55.8 g/mol,  m of HCl = 29.20 g,  M of HCl = 36.5 g/mol,  M of FeCl₂ = 126.8 g/mol\nStep 1 — convert each mass to moles:\nn(Fe) = 27.9 / 55.8 = 0.50 mol\nn(HCl) = 29.20 / 36.5 = 0.8000 mol\nStep 2 — identify the limiting reactant:\nmoles of HCl needed = 0.50 × (2 ÷ 1) = 1.0 mol — only 0.8000 mol is available, so HCl is limiting\nStep 3 — moles of product from the limiting reactant:\nmoles of FeCl₂ = 0.8000 × (1 ÷ 2) = 0.4000 mol\nStep 4 — convert the product moles to mass:\nm(FeCl₂) = 0.4000 × 126.8\nm(FeCl₂) = 50.72 g"
}

[
 {
  "value": 8.0,
  "misconception": "you started from the excess reactant Fe₂O₃ — the limiting reactant CO caps the product",
  "feedback": null
 },
 {
  "value": 9.0,
  "misconception": "you flipped the mole ratio — the coefficient of Fe goes on top and CO's underneath",
  "feedback": null
 },
 {
  "value": 6.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of CO (limiting) = 6.0 mol\nThe 4.0 mol of Fe₂O₃ is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of Fe = moles of CO × (coefficient of Fe ÷ coefficient of CO)\nSubstitute in the values, and calculate:\nmoles of Fe = 6.0 × (2 ÷ 3)\nmoles of Fe = 4.0 mol"
}

[
 {
  "value": 9.0,
  "misconception": "you started from the excess reactant PbO — the limiting reactant C caps the product",
  "feedback": null
 },
 {
  "value": 1.0,
  "misconception": "you flipped the mole ratio — the coefficient of Pb goes on top and C's underneath",
  "feedback": null
 },
 {
  "value": 2.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of C (limiting) = 2.0 mol\nThe 9.0 mol of PbO is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of Pb = moles of C × (coefficient of Pb ÷ coefficient of C)\nSubstitute in the values, and calculate:\nmoles of Pb = 2.0 × (2 ÷ 1)\nmoles of Pb = 4.0 mol"
}

[
 {
  "value": 38.1,
  "misconception": "you calculated from the excess reactant H₂ — using up 0.400 mol of CuO needs only 0.400 mol of H₂, and 0.60 mol is available, so CuO is limiting",
  "feedback": null
 },
 {
  "value": 33.0,
  "misconception": "you added the two reactant masses — the leftover excess H₂ is not part of the asked product",
  "feedback": null
 },
 {
  "value": 31.8,
  "misconception": "you used CuO's molar mass in the final step — the wanted substance Cu's molar mass is 63.5 g/mol",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of CuO = 31.8 g,  M of CuO = 79.5 g/mol,  m of H₂ = 1.2 g,  M of H₂ = 2.0 g/mol,  M of Cu = 63.5 g/mol\nStep 1 — convert each mass to moles:\nn(CuO) = 31.8 / 79.5 = 0.400 mol\nn(H₂) = 1.2 / 2.0 = 0.60 mol\nStep 2 — identify the limiting reactant:\nmoles of H₂ needed = 0.400 × (1 ÷ 1) = 0.400 mol — 0.60 mol is available, so CuO is limiting\nStep 3 — moles of product from the limiting reactant:\nmoles of Cu = 0.400 × (1 ÷ 1) = 0.400 mol\nStep 4 — convert the product moles to mass:\nm(Cu) = 0.400 × 63.5\nm(Cu) = 25.4 g"
}

[
 {
  "value": 4.5,
  "misconception": "you started from the excess reactant Al — the limiting reactant HCl caps the product",
  "feedback": null
 },
 {
  "value": 12.0,
  "misconception": "you flipped the mole ratio — the coefficient of H₂ goes on top and HCl's underneath",
  "feedback": null
 },
 {
  "value": 6.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of HCl (limiting) = 6.0 mol\nThe 3.0 mol of Al is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of H₂ = moles of HCl × (coefficient of H₂ ÷ coefficient of HCl)\nSubstitute in the values, and calculate:\nmoles of H₂ = 6.0 × (3 ÷ 6)\nmoles of H₂ = 3.0 mol"
}

[
 {
  "value": 4.5,
  "misconception": "you started from the excess reactant Mg — the limiting reactant TiCl₄ caps the product",
  "feedback": null
 },
 {
  "value": 9.0,
  "misconception": "you carried the excess reactant's moles across — the calculation must start from the limiting reactant TiCl₄",
  "feedback": null
 },
 {
  "value": 4.0,
  "misconception": "you used MgCl₂'s coefficient — the wanted substance is Ti, whose coefficient is 1",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of TiCl₄ (limiting) = 2.0 mol\nThe 9.0 mol of Mg is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of Ti = moles of TiCl₄ × (coefficient of Ti ÷ coefficient of TiCl₄)\nSubstitute in the values, and calculate:\nmoles of Ti = 2.0 × (1 ÷ 1)\nmoles of Ti = 2.0 mol"
}

[
 {
  "value": 37.3,
  "misconception": "you calculated from the excess reactant K — using up 0.5000 mol of K needs 0.2500 mol of Cl₂, and only 0.2000 mol is available, so Cl₂ is limiting",
  "feedback": null
 },
 {
  "value": 14.92,
  "misconception": "you skipped the mole-ratio step — each mole of Cl₂ makes TWO moles of KCl",
  "feedback": null
 },
 {
  "value": 33.73,
  "misconception": "you added the two reactant masses — the leftover excess K is not part of the product",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of K = 19.55 g,  M of K = 39.1 g/mol,  m of Cl₂ = 14.18 g,  M of Cl₂ = 70.9 g/mol,  M of KCl = 74.6 g/mol\nStep 1 — convert each mass to moles:\nn(K) = 19.55 / 39.1 = 0.5000 mol\nn(Cl₂) = 14.18 / 70.9 = 0.2000 mol\nStep 2 — identify the limiting reactant:\nmoles of Cl₂ needed = 0.5000 × (1 ÷ 2) = 0.2500 mol — only 0.2000 mol is available, so Cl₂ is limiting\nStep 3 — moles of product from the limiting reactant:\nmoles of KCl = 0.2000 × (2 ÷ 1) = 0.4000 mol\nStep 4 — convert the product moles to mass:\nm(KCl) = 0.4000 × 74.6\nm(KCl) = 29.84 g"
}

[
 {
  "value": 5.0,
  "misconception": "you started from the excess reactant Cu₂S — the limiting reactant O₂ caps the product",
  "feedback": null
 },
 {
  "value": 9.0,
  "misconception": "you flipped the mole ratio — the coefficient of Cu₂O goes on top and O₂'s underneath",
  "feedback": null
 },
 {
  "value": 6.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of O₂ (limiting) = 6.0 mol\nThe 5.0 mol of Cu₂S is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of Cu₂O = moles of O₂ × (coefficient of Cu₂O ÷ coefficient of O₂)\nSubstitute in the values, and calculate:\nmoles of Cu₂O = 6.0 × (2 ÷ 3)\nmoles of Cu₂O = 4.0 mol"
}

[
 {
  "value": 9.0,
  "misconception": "you started from the excess reactant Al — the limiting reactant Cr₂O₃ caps the product",
  "feedback": null
 },
 {
  "value": 1.0,
  "misconception": "you flipped the mole ratio — the coefficient of Cr goes on top and Cr₂O₃'s underneath",
  "feedback": null
 },
 {
  "value": 2.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of Cr₂O₃ (limiting) = 2.0 mol\nThe 9.0 mol of Al is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of Cr = moles of Cr₂O₃ × (coefficient of Cr ÷ coefficient of Cr₂O₃)\nSubstitute in the values, and calculate:\nmoles of Cr = 2.0 × (2 ÷ 1)\nmoles of Cr = 4.0 mol"
}

[
 {
  "value": 107.9,
  "misconception": "you calculated from the excess reactant H₂ — using up 0.20 mol of Ag₂O needs only 0.20 mol of H₂, and 0.50 mol is available, so Ag₂O is limiting",
  "feedback": null
 },
 {
  "value": 21.58,
  "misconception": "you skipped the mole-ratio step — each mole of Ag₂O releases TWO moles of Ag",
  "feedback": null
 },
 {
  "value": 47.34,
  "misconception": "you added the two reactant masses — the leftover excess H₂ is not part of the product",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Ag₂O = 46.34 g,  M of Ag₂O = 231.7 g/mol,  m of H₂ = 1.0 g,  M of H₂ = 2.0 g/mol,  M of Ag = 107.9 g/mol\nStep 1 — convert each mass to moles:\nn(Ag₂O) = 46.34 / 231.7 = 0.2000 mol\nn(H₂) = 1.0 / 2.0 = 0.50 mol\nStep 2 — identify the limiting reactant:\nmoles of H₂ needed = 0.2000 × (1 ÷ 1) = 0.2000 mol — 0.50 mol is available, so Ag₂O is limiting\nStep 3 — moles of product from the limiting reactant:\nmoles of Ag = 0.2000 × (2 ÷ 1) = 0.4000 mol\nStep 4 — convert the product moles to mass:\nm(Ag) = 0.4000 × 107.9\nm(Ag) = 43.16 g"
}

[
 {
  "value": 4.0,
  "misconception": "you started from the excess reactant WO₃ — the limiting reactant H₂ caps the product",
  "feedback": null
 },
 {
  "value": 18.0,
  "misconception": "you flipped the mole ratio — the coefficient of W goes on top and H₂'s underneath",
  "feedback": null
 },
 {
  "value": 6.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of H₂ (limiting) = 6.0 mol\nThe 4.0 mol of WO₃ is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of W = moles of H₂ × (coefficient of W ÷ coefficient of H₂)\nSubstitute in the values, and calculate:\nmoles of W = 6.0 × (1 ÷ 3)\nmoles of W = 2.0 mol"
}

[
 {
  "value": 3.0,
  "misconception": "you started from the excess reactant Si — the limiting reactant N₂ caps the product",
  "feedback": null
 },
 {
  "value": 8.0,
  "misconception": "you flipped the mole ratio — the coefficient of Si₃N₄ goes on top and N₂'s underneath",
  "feedback": null
 },
 {
  "value": 4.0,
  "misconception": "you carried the limiting reactant's moles straight across without the mole ratio",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nmoles of N₂ (limiting) = 4.0 mol\nThe 9.0 mol of Si is the excess reactant — it does not enter the calculation.\nWrite down the equation:\nmoles of Si₃N₄ = moles of N₂ × (coefficient of Si₃N₄ ÷ coefficient of N₂)\nSubstitute in the values, and calculate:\nmoles of Si₃N₄ = 4.0 × (1 ÷ 2)\nmoles of Si₃N₄ = 2.0 mol"
}

[
 {
  "value": 71.12,
  "misconception": "you calculated from the excess reactant Br₂ — using up 0.20 mol of Al needs only 0.30 mol of Br₂, and 0.40 mol is available, so Al is limiting",
  "feedback": null
 },
 {
  "value": 69.32,
  "misconception": "you added the two reactant masses — the leftover excess Br₂ is not part of the product",
  "feedback": null
 },
 {
  "value": 5.4,
  "misconception": "you used Al's molar mass in the final step — the wanted substance AlBr₃'s molar mass is 266.7 g/mol",
  "feedback": null
 }
]

{
 "keyExplanation": "Write down the values in the question:\nm of Al = 5.400 g,  M of Al = 27.0 g/mol,  m of Br₂ = 63.92 g,  M of Br₂ = 159.8 g/mol,  M of AlBr₃ = 266.7 g/mol\nStep 1 — convert each mass to moles:\nn(Al) = 5.400 / 27.0 = 0.2000 mol\nn(Br₂) = 63.92 / 159.8 = 0.40 mol\nStep 2 — identify the limiting reactant:\nmoles of Br₂ needed = 0.2000 × (3 ÷ 2) = 0.3000 mol — 0.40 mol is available, so Al is limiting\nStep 3 — moles of product from the limiting reactant:\nmoles of AlBr₃ = 0.2000 × (2 ÷ 2) = 0.2000 mol\nStep 4 — convert the product moles to mass:\nm(AlBr₃) = 0.2000 × 266.7\nm(AlBr₃) = 53.34 g"
}

[
 {
  "value": 111.1,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.9,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 2.5,
  "misconception": "you subtracted the yields — percent yield compares them by division, not by difference",
  "feedback": "This answer is wrong — you subtracted the yields — percent yield compares them by division, not by difference."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 22.5 g\ntheoretical yield = 25.0 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (22.5 ÷ 25.0) × 100\npercent yield = 90.0%"
}

[
 {
  "value": 2.2,
  "misconception": "you divided instead of multiplying — n = M × V multiplies the molarity by the volume",
  "feedback": "This answer is wrong — you divided instead of multiplying — n = M × V multiplies the molarity by the volume."
 },
 {
  "value": 0.11,
  "misconception": "you doubled the moles with KCl's coefficient — BaSO₄'s ratio to BaCl₂ is 1 : 1",
  "feedback": "This answer is wrong — you doubled the moles with KCl's coefficient — BaSO₄'s ratio to BaCl₂ is 1 : 1."
 }
]

{
 "keyExplanation": "Step 1 — moles of dissolved reactant:\nn(BaCl₂) = M × V\nn(BaCl₂) = 0.16 × 0.35 = 0.056 mol\nStep 2 — moles of product with the mole ratio:\nmoles of BaSO₄ = 0.056 × (1 ÷ 1)\nmoles of BaSO₄ = 0.056 mol"
}

[
 {
  "value": 400,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.25,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 42,
  "misconception": "you subtracted the actual yield from the theoretical yield and reported the difference as a percent",
  "feedback": "This answer is wrong — you subtracted the actual yield from the theoretical yield and reported the difference as a percent."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 14 g\ntheoretical yield = 56 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (14 ÷ 56) × 100\npercent yield = 25.0%\nThe actual yield is far below the theoretical yield, so the percentage must come out well below 100% — an answer like 400% fails that check."
}

[
 {
  "value": 397.7,
  "misconception": "you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 175 g",
  "feedback": "This answer is wrong — you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 175 g."
 },
 {
  "value": 7700,
  "misconception": "you forgot to divide the percent yield by 100 — thousands of grams from a 175 g prediction is the signal",
  "feedback": "This answer is wrong — you forgot to divide the percent yield by 100 — thousands of grams from a 175 g prediction is the signal."
 },
 {
  "value": 131,
  "misconception": "you subtracted the percent number from the theoretical yield as if it were a mass in grams — 44 is a percentage, not a mass",
  "feedback": "This answer is wrong — you subtracted the percent number from the theoretical yield as if it were a mass in grams — 44 is a percentage, not a mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\npercent yield = 44%\ntheoretical yield = 175 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nMake the actual yield the subject:\nactual yield = (percent yield ÷ 100) × theoretical yield\nSubstitute in the values, and calculate:\nactual yield = (44 ÷ 100) × 175\nactual yield = 77 g\nSanity check: 77 g is below the theoretical 175 g — a percent yield below 100% must give an actual yield below the theoretical yield."
}

[
 {
  "value": 44.8,
  "misconception": "you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 28.05 g",
  "feedback": "This answer is wrong — you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 28.05 g."
 },
 {
  "value": 125,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(CaCO₃) = 50.05 / 100.1 = 0.500 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of CaO = 0.500 × (1 ÷ 1) = 0.500 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.500 × 56.1 = 28.05 g\nStep 4 — calculate the percent yield:\npercent yield = (22.44 ÷ 28.05) × 100\npercent yield = 80.0%"
}

[
 {
  "value": 240.0,
  "misconception": "you used the volume in milliliters — n = M × V needs liters, and 750 mL is 0.750 L",
  "feedback": "This answer is wrong — you used the volume in milliliters — n = M × V needs liters, and 750 mL is 0.750 L."
 },
 {
  "value": 0.32,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 2.34,
  "misconception": "you divided the volume by the molarity instead of multiplying them",
  "feedback": "This answer is wrong — you divided the volume by the molarity instead of multiplying them."
 }
]

{
 "keyExplanation": "Convert the volume to liters first: 750 mL = 0.750 L.\nStep 1 — moles of dissolved reactant:\nn(SrCl₂) = M × V\nn(SrCl₂) = 0.32 × 0.750 = 0.24 mol\nStep 2 — moles of product with the mole ratio:\nmoles of SrSO₄ = 0.24 × (1 ÷ 1)\nmoles of SrSO₄ = 0.24 mol\nA 240 mol answer fails the sanity check — three-quarters of a liter of a dilute solution holds well under a mole of solute."
}

[
 {
  "value": 0.5,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 99.8,
  "misconception": "you compared the product mass with the reactant mass — the theoretical yield is 25.64 g of SO₂, not 12.84 g",
  "feedback": "This answer is wrong — you compared the product mass with the reactant mass — the theoretical yield is 25.64 g of SO₂, not 12.84 g."
 },
 {
  "value": 200.0,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(S) = 12.84 / 32.1 = 0.400 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of SO₂ = 0.400 × (1 ÷ 1) = 0.400 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.400 × 64.1 = 25.64 g\nStep 4 — calculate the percent yield:\npercent yield = (12.82 ÷ 25.64) × 100\npercent yield = 50.0%\nThe near-match between 12.82 g of product and 12.84 g of reactant is a coincidence of masses — the yield comparison is always against the theoretical yield."
}

[
 {
  "value": 108.1,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.925,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 2.4,
  "misconception": "you subtracted the yields — percent yield compares them by division, not by difference",
  "feedback": "This answer is wrong — you subtracted the yields — percent yield compares them by division, not by difference."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 29.6 g\ntheoretical yield = 32.0 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (29.6 ÷ 32.0) × 100\npercent yield = 92.5%"
}

[
 {
  "value": 0.066,
  "misconception": "you stopped at the moles of KOH — the mole ratio of Sn(OH)₂ to KOH is 1 : 2",
  "feedback": "This answer is wrong — you stopped at the moles of KOH — the mole ratio of Sn(OH)₂ to KOH is 1 : 2."
 },
 {
  "value": 0.13,
  "misconception": "you flipped the mole ratio and doubled the KOH moles instead of halving them",
  "feedback": "This answer is wrong — you flipped the mole ratio and doubled the KOH moles instead of halving them."
 }
]

{
 "keyExplanation": "Step 1 — moles of dissolved reactant:\nn(KOH) = M × V\nn(KOH) = 0.15 × 0.44 = 0.066 mol\nStep 2 — moles of product with the mole ratio:\nmoles of Sn(OH)₂ = 0.066 × (1 ÷ 2)\nmoles of Sn(OH)₂ = 0.033 mol"
}

[
 {
  "value": 500,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.2,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 132,
  "misconception": "you subtracted the actual yield from the theoretical yield and reported the difference as a percent",
  "feedback": "This answer is wrong — you subtracted the actual yield from the theoretical yield and reported the difference as a percent."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 33 g\ntheoretical yield = 165 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (33 ÷ 165) × 100\npercent yield = 20.0%\nThe actual yield is far below the theoretical yield, so the percentage must come out well below 100% — an answer like 500% fails that check."
}

[
 {
  "value": 2031.25,
  "misconception": "you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 325 g",
  "feedback": "This answer is wrong — you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 325 g."
 },
 {
  "value": 5200,
  "misconception": "you forgot to divide the percent yield by 100 — thousands of grams from a 325 g prediction is the signal",
  "feedback": "This answer is wrong — you forgot to divide the percent yield by 100 — thousands of grams from a 325 g prediction is the signal."
 },
 {
  "value": 309,
  "misconception": "you subtracted the percent number from the theoretical yield as if it were a mass in grams — 16 is a percentage, not a mass",
  "feedback": "This answer is wrong — you subtracted the percent number from the theoretical yield as if it were a mass in grams — 16 is a percentage, not a mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\npercent yield = 16%\ntheoretical yield = 325 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nMake the actual yield the subject:\nactual yield = (percent yield ÷ 100) × theoretical yield\nSubstitute in the values, and calculate:\nactual yield = (16 ÷ 100) × 325\nactual yield = 52 g\nSanity check: 52 g is below the theoretical 325 g — a percent yield below 100% must give an actual yield below the theoretical yield."
}

[
 {
  "value": 37.0,
  "misconception": "you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 35.45 g",
  "feedback": "This answer is wrong — you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 35.45 g."
 },
 {
  "value": 167,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(MnCO₃) = 57.45 / 114.9 = 0.500 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of MnO = 0.500 × (1 ÷ 1) = 0.500 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.500 × 70.9 = 35.45 g\nStep 4 — calculate the percent yield:\npercent yield = (21.27 ÷ 35.45) × 100\npercent yield = 60.0%"
}

[
 {
  "value": 680.0,
  "misconception": "you used the volume in milliliters — n = M × V needs liters, and 800 mL is 0.800 L",
  "feedback": "This answer is wrong — you used the volume in milliliters — n = M × V needs liters, and 800 mL is 0.800 L."
 },
 {
  "value": 0.85,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 0.94,
  "misconception": "you divided the volume by the molarity instead of multiplying them",
  "feedback": "This answer is wrong — you divided the volume by the molarity instead of multiplying them."
 }
]

{
 "keyExplanation": "Convert the volume to liters first: 800 mL = 0.800 L.\nStep 1 — moles of dissolved reactant:\nn(Pb(NO₃)₂) = M × V\nn(Pb(NO₃)₂) = 0.85 × 0.800 = 0.68 mol\nStep 2 — moles of product with the mole ratio:\nmoles of PbSO₄ = 0.68 × (1 ÷ 1)\nmoles of PbSO₄ = 0.68 mol\nA 680 mol answer fails the sanity check — less than a liter of solution holds well under a mole of dissolved salt at this molarity."
}

[
 {
  "value": 142.9,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 94.6,
  "misconception": "you compared the product mass with the reactant mass — the theoretical yield is 6.16 g of ZrO₂, not 4.56 g",
  "feedback": "This answer is wrong — you compared the product mass with the reactant mass — the theoretical yield is 6.16 g of ZrO₂, not 4.56 g."
 },
 {
  "value": 0.7,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(Zr) = 4.56 / 91.2 = 0.0500 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of ZrO₂ = 0.0500 × (1 ÷ 1) = 0.0500 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.0500 × 123.2 = 6.16 g\nStep 4 — calculate the percent yield:\npercent yield = (4.312 ÷ 6.16) × 100\npercent yield = 70.0%\nThe collected ZrO₂ mass sitting just below the zirconium mass is a coincidence of masses — the oxide carries added oxygen mass, and the yield comparison is always against the theoretical yield."
}

[
 {
  "value": 114.3,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.875,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 3.1,
  "misconception": "you subtracted the yields — percent yield compares them by division, not by difference",
  "feedback": "This answer is wrong — you subtracted the yields — percent yield compares them by division, not by difference."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 21.7 g\ntheoretical yield = 24.8 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (21.7 ÷ 24.8) × 100\npercent yield = 87.5%"
}

[
 {
  "value": 0.14,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 0.15,
  "misconception": "you doubled the moles with KCl's coefficient — MnCO₃'s ratio to MnCl₂ is 1 : 1",
  "feedback": "This answer is wrong — you doubled the moles with KCl's coefficient — MnCO₃'s ratio to MnCl₂ is 1 : 1."
 }
]

{
 "keyExplanation": "Step 1 — moles of dissolved reactant:\nn(MnCl₂) = M × V\nn(MnCl₂) = 0.14 × 0.55 = 0.077 mol\nStep 2 — moles of product with the mole ratio:\nmoles of MnCO₃ = 0.077 × (1 ÷ 1)\nmoles of MnCO₃ = 0.077 mol"
}

[
 {
  "value": 308,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.325,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 86.4,
  "misconception": "you subtracted the actual yield from the theoretical yield and reported the difference as a percent",
  "feedback": "This answer is wrong — you subtracted the actual yield from the theoretical yield and reported the difference as a percent."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 41.6 g\ntheoretical yield = 128 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (41.6 ÷ 128) × 100\npercent yield = 32.5%\nThe actual yield is far below the theoretical yield, so the percentage must come out well below 100% — an answer like 308% fails that check."
}

[
 {
  "value": 1764.7,
  "misconception": "you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 300 g",
  "feedback": "This answer is wrong — you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 300 g."
 },
 {
  "value": 5100,
  "misconception": "you forgot to divide the percent yield by 100 — thousands of grams from a 300 g prediction is the signal",
  "feedback": "This answer is wrong — you forgot to divide the percent yield by 100 — thousands of grams from a 300 g prediction is the signal."
 },
 {
  "value": 283,
  "misconception": "you subtracted the percent number from the theoretical yield as if it were a mass in grams — 17 is a percentage, not a mass",
  "feedback": "This answer is wrong — you subtracted the percent number from the theoretical yield as if it were a mass in grams — 17 is a percentage, not a mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\npercent yield = 17%\ntheoretical yield = 300 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nMake the actual yield the subject:\nactual yield = (percent yield ÷ 100) × theoretical yield\nSubstitute in the values, and calculate:\nactual yield = (17 ÷ 100) × 300\nactual yield = 51 g\nSanity check: 51 g is below the theoretical 300 g — a percent yield below 100% must give an actual yield below the theoretical yield."
}

[
 {
  "value": 104,
  "misconception": "you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 63.92 g; comparing with the metal's mass even pushes the result past 100, which a genuine yield can never do",
  "feedback": "This answer is wrong — you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 63.92 g; comparing with the metal's mass even pushes the result past 100, which a genuine yield can never do."
 },
 {
  "value": 160,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(Ti) = 38.32 / 47.9 = 0.800 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of TiO₂ = 0.800 × (1 ÷ 1) = 0.800 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.800 × 79.9 = 63.92 g\nStep 4 — calculate the percent yield:\npercent yield = (39.95 ÷ 63.92) × 100\npercent yield = 62.5%"
}

[
 {
  "value": 91.0,
  "misconception": "you used the volume in milliliters — n = M × V needs liters, and 700 mL is 0.700 L",
  "feedback": "This answer is wrong — you used the volume in milliliters — n = M × V needs liters, and 700 mL is 0.700 L."
 },
 {
  "value": 0.13,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 5.38,
  "misconception": "you divided the volume by the molarity instead of multiplying them",
  "feedback": "This answer is wrong — you divided the volume by the molarity instead of multiplying them."
 }
]

{
 "keyExplanation": "Convert the volume to liters first: 700 mL = 0.700 L.\nStep 1 — moles of dissolved reactant:\nn(BaCl₂) = M × V\nn(BaCl₂) = 0.13 × 0.700 = 0.091 mol\nStep 2 — moles of product with the mole ratio:\nmoles of BaCO₃ = 0.091 × (1 ÷ 1)\nmoles of BaCO₃ = 0.091 mol\nA 91 mol answer fails the sanity check — under a liter of a dilute solution holds well under a mole of dissolved salt."
}

[
 {
  "value": 222.2,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 96.2,
  "misconception": "you compared the product mass with the reactant mass — the theoretical yield is 12.02 g of SiO₂, not 5.62 g",
  "feedback": "This answer is wrong — you compared the product mass with the reactant mass — the theoretical yield is 12.02 g of SiO₂, not 5.62 g."
 },
 {
  "value": 0.45,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(Si) = 5.62 / 28.1 = 0.200 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of SiO₂ = 0.200 × (1 ÷ 1) = 0.200 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.200 × 60.1 = 12.02 g\nStep 4 — calculate the percent yield:\npercent yield = (5.409 ÷ 12.02) × 100\npercent yield = 45.0%\nThe collected SiO₂ mass sitting just below the silicon mass is a coincidence of masses — the yield comparison is always against the theoretical yield, not the reactant mass."
}

[
 {
  "value": 113.6,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.88,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 6.3,
  "misconception": "you subtracted the yields — percent yield compares them by division, not by difference",
  "feedback": "This answer is wrong — you subtracted the yields — percent yield compares them by division, not by difference."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 46.2 g\ntheoretical yield = 52.5 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (46.2 ÷ 52.5) × 100\npercent yield = 88.0%"
}

[
 {
  "value": 0.11,
  "misconception": "you stopped at the moles of K₃PO₄ — the mole ratio of Ni₃(PO₄)₂ to K₃PO₄ is 1 : 2",
  "feedback": "This answer is wrong — you stopped at the moles of K₃PO₄ — the mole ratio of Ni₃(PO₄)₂ to K₃PO₄ is 1 : 2."
 },
 {
  "value": 0.22,
  "misconception": "you flipped the mole ratio and doubled the K₃PO₄ moles instead of halving them",
  "feedback": "This answer is wrong — you flipped the mole ratio and doubled the K₃PO₄ moles instead of halving them."
 }
]

{
 "keyExplanation": "Step 1 — moles of dissolved reactant:\nn(K₃PO₄) = M × V\nn(K₃PO₄) = 0.90 × 0.12 = 0.108 mol\nStep 2 — moles of product with the mole ratio:\nmoles of Ni₃(PO₄)₂ = 0.108 × (1 ÷ 2)\nmoles of Ni₃(PO₄)₂ = 0.054 mol"
}

[
 {
  "value": 571,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.175,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 62.7,
  "misconception": "you subtracted the actual yield from the theoretical yield and reported the difference as a percent",
  "feedback": "This answer is wrong — you subtracted the actual yield from the theoretical yield and reported the difference as a percent."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 13.3 g\ntheoretical yield = 76.0 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (13.3 ÷ 76) × 100\npercent yield = 17.5%\nThe actual yield is far below the theoretical yield, so the percentage must come out well below 100% — an answer like 571% fails that check."
}

[
 {
  "value": 982.1,
  "misconception": "you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 275 g",
  "feedback": "This answer is wrong — you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 275 g."
 },
 {
  "value": 7700,
  "misconception": "you forgot to divide the percent yield by 100 — thousands of grams from a 275 g prediction is the signal",
  "feedback": "This answer is wrong — you forgot to divide the percent yield by 100 — thousands of grams from a 275 g prediction is the signal."
 },
 {
  "value": 247,
  "misconception": "you subtracted the percent number from the theoretical yield as if it were a mass in grams — 28 is a percentage, not a mass",
  "feedback": "This answer is wrong — you subtracted the percent number from the theoretical yield as if it were a mass in grams — 28 is a percentage, not a mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\npercent yield = 28%\ntheoretical yield = 275 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nMake the actual yield the subject:\nactual yield = (percent yield ÷ 100) × theoretical yield\nSubstitute in the values, and calculate:\nactual yield = (28 ÷ 100) × 275\nactual yield = 77 g\nSanity check: 77 g is below the theoretical 275 g — a percent yield below 100% must give an actual yield below the theoretical yield."
}

[
 {
  "value": 111,
  "misconception": "you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 59.76 g; comparing with the metal's mass even pushes the result past 100, which a genuine yield can never do",
  "feedback": "This answer is wrong — you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 59.76 g; comparing with the metal's mass even pushes the result past 100, which a genuine yield can never do."
 },
 {
  "value": 114,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(Ni) = 46.96 / 58.7 = 0.800 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of NiO = 0.800 × (2 ÷ 2) = 0.800 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.800 × 74.7 = 59.76 g\nStep 4 — calculate the percent yield:\npercent yield = (52.29 ÷ 59.76) × 100\npercent yield = 87.5%"
}

[
 {
  "value": 880.0,
  "misconception": "you used the volume in milliliters — n = M × V needs liters, and 550 mL is 0.550 L",
  "feedback": "This answer is wrong — you used the volume in milliliters — n = M × V needs liters, and 550 mL is 0.550 L."
 },
 {
  "value": 1.6,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 0.34,
  "misconception": "you divided the volume by the molarity instead of multiplying them",
  "feedback": "This answer is wrong — you divided the volume by the molarity instead of multiplying them."
 }
]

{
 "keyExplanation": "Convert the volume to liters first: 550 mL = 0.550 L.\nStep 1 — moles of dissolved reactant:\nn(MnSO₄) = M × V\nn(MnSO₄) = 1.6 × 0.550 = 0.88 mol\nStep 2 — moles of product with the mole ratio:\nmoles of MnCO₃ = 0.88 × (1 ÷ 1)\nmoles of MnCO₃ = 0.88 mol\nA 880 mol answer fails the sanity check — just over half a liter of solution holds around a mole of solute at this concentration, not hundreds."
}

[
 {
  "value": 140.8,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 99.8,
  "misconception": "you compared the product mass with the reactant mass — the theoretical yield is 11.10 g of SeO₂, not 7.90 g",
  "feedback": "This answer is wrong — you compared the product mass with the reactant mass — the theoretical yield is 11.10 g of SeO₂, not 7.90 g."
 },
 {
  "value": 0.71,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(Se) = 7.90 / 79.0 = 0.100 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of SeO₂ = 0.100 × (1 ÷ 1) = 0.100 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.100 × 111.0 = 11.10 g\nStep 4 — calculate the percent yield:\npercent yield = (7.881 ÷ 11.10) × 100\npercent yield = 71.0%\nThe near-match between 7.881 g of product and 7.90 g of reactant is a coincidence of masses — the yield comparison is always against the theoretical yield."
}

[
 {
  "value": 106,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.94,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 1.8,
  "misconception": "you subtracted the yields — percent yield compares them by division, not by difference",
  "feedback": "This answer is wrong — you subtracted the yields — percent yield compares them by division, not by difference."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 28.2 g\ntheoretical yield = 30.0 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (28.2 ÷ 30.0) × 100\npercent yield = 94.0%"
}

[
 {
  "value": 0.18,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 0.16,
  "misconception": "you doubled the moles with KCl's coefficient — CoCO₃'s ratio to CoCl₂ is 1 : 1",
  "feedback": "This answer is wrong — you doubled the moles with KCl's coefficient — CoCO₃'s ratio to CoCl₂ is 1 : 1."
 }
]

{
 "keyExplanation": "Step 1 — moles of dissolved reactant:\nn(CoCl₂) = M × V\nn(CoCl₂) = 0.18 × 0.45 = 0.081 mol\nStep 2 — moles of product with the mole ratio:\nmoles of CoCO₃ = 0.081 × (1 ÷ 1)\nmoles of CoCO₃ = 0.081 mol"
}

[
 {
  "value": 426,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 0.235,
  "misconception": "you forgot to multiply the fraction by 100",
  "feedback": "This answer is wrong — you forgot to multiply the fraction by 100."
 },
 {
  "value": 153,
  "misconception": "you subtracted the actual yield from the theoretical yield and reported the difference as a percent",
  "feedback": "This answer is wrong — you subtracted the actual yield from the theoretical yield and reported the difference as a percent."
 }
]

{
 "keyExplanation": "Write down the values in the question:\nactual yield = 47 g\ntheoretical yield = 200 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nSubstitute in the values, and calculate:\npercent yield = (47 ÷ 200) × 100\npercent yield = 23.5%\nThe actual yield is far below the theoretical yield, so the percentage must come out well below 100% — an answer like 426% fails that check."
}

[
 {
  "value": 5600,
  "misconception": "you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 675 g",
  "feedback": "This answer is wrong — you divided the theoretical yield by the percent fraction instead of multiplying — a below-100% yield must give an actual yield below the theoretical 675 g."
 },
 {
  "value": 8100,
  "misconception": "you forgot to divide the percent yield by 100 — thousands of grams from a 675 g prediction is the signal",
  "feedback": "This answer is wrong — you forgot to divide the percent yield by 100 — thousands of grams from a 675 g prediction is the signal."
 },
 {
  "value": 663,
  "misconception": "you subtracted the percent number from the theoretical yield as if it were a mass in grams — 12 is a percentage, not a mass",
  "feedback": "This answer is wrong — you subtracted the percent number from the theoretical yield as if it were a mass in grams — 12 is a percentage, not a mass."
 }
]

{
 "keyExplanation": "Write down the values in the question:\npercent yield = 12%\ntheoretical yield = 675 g\nWrite down the equation:\npercent yield = (actual yield ÷ theoretical yield) × 100\nMake the actual yield the subject:\nactual yield = (percent yield ÷ 100) × theoretical yield\nSubstitute in the values, and calculate:\nactual yield = (12 ÷ 100) × 675\nactual yield = 81 g\nSanity check: 81 g is below the theoretical 675 g — a percent yield below 100% must give an actual yield below the theoretical yield."
}

[
 {
  "value": 42.5,
  "misconception": "you skipped the mole-ratio step — 0.400 mol is the chromium's moles, and every 4 mol of Cr makes only 2 mol of Cr₂O₃",
  "feedback": "This answer is wrong — you skipped the mole-ratio step — 0.400 mol is the chromium's moles, and every 4 mol of Cr makes only 2 mol of Cr₂O₃."
 },
 {
  "value": 118,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 124,
  "misconception": "you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 30.40 g; comparing with the metal's mass even pushes the result past 100, which a genuine yield can never do",
  "feedback": "This answer is wrong — you divided the product mass by the reactant mass — the comparison is with the theoretical yield, 30.40 g; comparing with the metal's mass even pushes the result past 100, which a genuine yield can never do."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(Cr) = 20.8 / 52.0 = 0.400 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of Cr₂O₃ = 0.400 × (2 ÷ 4) = 0.200 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.200 × 152.0 = 30.40 g\nStep 4 — calculate the percent yield:\npercent yield = (25.84 ÷ 30.40) × 100\npercent yield = 85.0%"
}

[
 {
  "value": 460.0,
  "misconception": "you used the volume in milliliters — n = M × V needs liters, and 500 mL is 0.500 L",
  "feedback": "This answer is wrong — you used the volume in milliliters — n = M × V needs liters, and 500 mL is 0.500 L."
 },
 {
  "value": 0.92,
  "misconception": "you used the molarity as the mole amount without multiplying by the volume",
  "feedback": "This answer is wrong — you used the molarity as the mole amount without multiplying by the volume."
 },
 {
  "value": 0.54,
  "misconception": "you divided the volume by the molarity instead of multiplying them",
  "feedback": "This answer is wrong — you divided the volume by the molarity instead of multiplying them."
 }
]

{
 "keyExplanation": "Convert the volume to liters first: 500 mL = 0.500 L.\nStep 1 — moles of dissolved reactant:\nn(H₂SO₄) = M × V\nn(H₂SO₄) = 0.92 × 0.500 = 0.46 mol\nStep 2 — moles of product with the mole ratio:\nmoles of MnSO₄ = 0.46 × (1 ÷ 1)\nmoles of MnSO₄ = 0.46 mol\nA 460 mol answer fails the sanity check — half a liter of a dilute acid holds well under a mole of solute."
}

[
 {
  "value": 286,
  "misconception": "you divided the theoretical yield by the actual yield — the measured amount goes on top",
  "feedback": "This answer is wrong — you divided the theoretical yield by the actual yield — the measured amount goes on top."
 },
 {
  "value": 113,
  "misconception": "you compared the product mass with the reactant mass — a collected mass above the boron mass is possible because the oxide gains oxygen; the theoretical yield is 17.4 g of B₂O₃",
  "feedback": "This answer is wrong — you compared the product mass with the reactant mass — a collected mass above the boron mass is possible because the oxide gains oxygen; the theoretical yield is 17.4 g of B₂O₃."
 },
 {
  "value": 17.5,
  "misconception": "you skipped the mole ratio — every 4 mol of B makes only 2 mol of B₂O₃",
  "feedback": "This answer is wrong — you skipped the mole ratio — every 4 mol of B makes only 2 mol of B₂O₃."
 }
]

{
 "keyExplanation": "Step 1 — convert the reactant mass to moles:\nn(B) = 5.40 / 10.8 = 0.500 mol\nStep 2 — convert to moles of product with the mole ratio:\nmoles of B₂O₃ = 0.500 × (2 ÷ 4) = 0.250 mol\nStep 3 — convert the product moles to mass (the theoretical yield):\ntheoretical yield = 0.250 × 69.6 = 17.4 g\nStep 4 — calculate the percent yield:\npercent yield = (6.09 ÷ 17.4) × 100\npercent yield = 35.0%\nCollecting more grams of B₂O₃ (6.09 g) than the boron burned (5.40 g) is not a contradiction — the oxide carries added oxygen mass — and the yield comparison is always against the theoretical yield."
}