# Propanoic acid is a carboxylic acid found in some dairy products. Explain why propanoic acid is described as a weak acid, and describe two chemical properties it shares with stronger acids such as hydrochloric acid.

> WJEC A-Level Chemistry (Wales) — 4.5 Carboxylic acids and their derivatives · Explain · 5 marks

> Propanoic acid has the molecular formula CH₃CH₂COOH. It is a weak acid that dissolves in water to form an acidic solution.

## Mark scheme (5 marks)

1. Propanoic acid is a weak acid because it only partially/incompletely dissociates (ionises) in water
2. Propanoic acid reacts with metals (e.g. magnesium/zinc) to produce a salt and hydrogen gas
3. Correct description of the salt formed in the metal reaction — named as a propanoate salt
4. Propanoic acid reacts with bases/alkalis to produce a salt and water (neutralisation)
5. Propanoic acid reacts with carbonates/metal carbonates to produce a salt, water, and carbon dioxide

## Key terms

- [weak acid](https://www.gradenine.co.uk/glossary/weak-acid)

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/propanoic-acid-is-a-carboxylic-acid-f824bdd1) · Published by Druglandscape Ltd.