O Levels Chemistry (5070)•5070/11/M/J/19

Explanation
Combustion stoichiometry and molar volume at RTP Steps:
- Balance the combustion equation for complete reaction: C₁₂H₂₂O₁₁ + 6 O₂ → 12 CO₂ + 11 H₂O.
- The equation shows 1 mole of sugar (C₁₂H₂₂O₁₁) requires 6 moles of O₂.
- At RTP, the molar volume of any gas is 24 dm³ per mole.
- Calculate volume: 6 moles O₂ × 24 dm³/mol = 144 dm³.
Why C is correct:
- Stoichiometric ratio from balanced equation gives 6 moles O₂, multiplied by RTP molar volume (24 dm³/mol) yields 144 dm³.
Why the others are wrong:
- A: Equals 1 mole O₂ (24 dm³), ignores full reaction needs.
- B: Equals 1.5 moles O₂ (36 dm³), underestimates stoichiometry.
- D: Equals 9 moles O₂ (216 dm³), overestimates O₂ required.
Final answer: C
Topic: The mole and the Avogadro constant
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