# Ethanoic acid reacts with ethanol to form an ester and water. Describe the properties of ethanoic acid that show it is a weak acid, and explain what is meant by the term 'ester' in the context of this reaction. Include the name of the functional group present in ethanoic acid and state one use of the ester formed.

> WJEC A-Level Chemistry (Wales) — 3.4 Carbonyls and acids · Describe · 5 marks

> Ethanoic acid (CH₃COOH) belongs to the carboxylic acid homologous series. When it reacts with ethanol (CH₃CH₂OH) in the presence of an acid catalyst, an ester called ethyl ethanoate is formed.

## Mark scheme (5 marks)

1. Ethanoic acid is a weak acid because it only partially dissociates / ionises in water (not fully dissociated)
2. Ethanoic acid produces a lower concentration of H⁺ ions / has a higher pH than a strong acid of the same concentration
3. The functional group in ethanoic acid is the carboxyl group (–COOH)
4. An ester is the compound formed when a carboxylic acid reacts with an alcohol / the –OH from the acid and –OH from the alcohol combine and water is eliminated
5. One correct use of ethyl ethanoate / esters — e.g. as a solvent, in perfumes, in flavourings, or in food flavouring

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/ethanoic-acid-reacts-with-ethanol-to-8ab1e7e8) · Published by Druglandscape Ltd.