# Explain the difference between a strong acid and a weak acid.

> Edexcel GCSE Chemistry (1CH0) — 3.1 Acids · Explain · 4 marks

> Hydrochloric acid and ethanoic acid are both acids, but they behave differently when dissolved in water.

## Mark scheme (4 marks)

1. A strong acid is completely ionised in aqueous solution
2. A weak acid is only partially ionised in aqueous solution
3. Therefore a strong acid has a higher concentration of H+ ions than a weak acid (at the same overall concentration)
4. A strong acid has a lower pH than a weak acid of the same concentration, with a correct example of each type

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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/explain-the-difference-between-a-strong-8cbf50bf) · Published by Druglandscape Ltd.