Ethanol can be oxidised to produce ethanoic acid. State the name of the functional group present in ethanoic acid, give the molecular formula of ethanoic acid, and state one use of ethanoic acid.

Cambridge International IGCSE Chemistry (0620) — 11.7 Carboxylic acids · State · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Ethanoic acid is a carboxylic acid that can be produced by the oxidation of ethanol. It is a weak acid that reacts with alcohols to form esters.

Model answer (4 marks)

Functional group: carboxyl group (–COOH)
Molecular formula: C2H4O2
Use 1: vinegar (acetic acid) flavouring and preservative
Use 2: weak acid – partially dissociates in water

Examiner tips

Use the exact term "carboxyl group (–COOH)" for full credit
Write the formula as C2H4O2, not CH3COOH
Mention a common use such as vinegar, then add the weak‑acid property

Common mistakes

Writing the formula as CH3COOH instead of C2H4O2
Omitting the carboxyl group name or writing a different functional group
Failing to include a second use or the weak‑acid property

Mark scheme (4 marks)

Names the carboxyl group (–COOH) as the functional group in ethanoic acid
Gives the correct molecular formula of ethanoic acid
States a correct use of ethanoic acid (first creditworthy use)
States a second distinct correct use of ethanoic acid OR identifies that ethanoic acid is a weak acid (i.e. partially dissociates / does not fully ionise in water)

Key terms in this question

functional group · molecular formula