O Levels Chemistry (5070)•5070/12/M/J/24
Explanation
Stoichiometry of alcohol combustion reactions
Steps:
- Use general combustion formula for alcohols C_xH_{2x+2}O + (3x/2)O_2 → xCO_2 + (x+1)H_2O.
- For butanols (x=4): requires 6 moles O_2 per mole alcohol.
- For propanols (x=3): requires 4.5 moles O_2 per mole alcohol.
- Isomer position (1-ol vs. 2-ol) does not change molecular formula or O_2 requirement.
Why A is correct:
- Butan-1-ol (C_4H_9OH) combusts as C_4H_{10}O + 6O_2 → 4CO_2 + 5H_2O, requiring 6 moles O_2.
Why the others are wrong:
- B: Butan-2-ol has same formula as butan-1-ol, requiring 6 moles O_2, not 12.
- C: Propan-1-ol requires 4.5 moles O_2, not 3.
- D: Propan-2-ol requires 4.5 moles O_2, not 6.
Final answer: A
Topic: Alcohols
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