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O Levels Chemistry (5070)•5070/12/M/J/19
Question 34 from 5070/12/M/J/19

Explanation

Oxygen Requirement in Combustion Equations

Steps:

  • Write balanced combustion equations for each compound to CO2 and H2O.
  • Determine moles of O2 per mole of compound from the O2 coefficient.
  • Compare values: CH3OH (1.5), CH3COOH (2), C2H6 (3.5), C2H2 (2.5).
  • Select the compound with the minimum O2 moles.

Why A is correct:

  • CH3OH contains oxygen in its structure, minimizing external O2 needed per the combustion formula adjusted for inherent oxygen.

Why the others are wrong:

  • B requires 2 moles of O2 due to two carbons and less inherent oxygen.
  • C requires 3.5 moles of O2 as a saturated hydrocarbon with high H content.
  • D requires 2.5 moles of O2 from its unsaturated triple bond structure.

Final answer: A

Topic: Fuels

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