# A student adds sodium carbonate powder to two separate beakers, one containing dilute hydrochloric acid and one containing dilute ethanoic acid of the same concentration. Both reactions produce carbon dioxide gas. Explain why the rate of fizzing is faster in the hydrochloric acid, even though both acids have the same concentration.

> Eduqas A-Level Chemistry — 3.9 Acid-base equilibria · Explain · 5 marks

## Mark scheme (5 marks)

1. Hydrochloric acid is a strong acid
2. Hydrochloric acid fully/completely dissociates into ions in solution
3. Ethanoic acid is a weak acid and only partially dissociates
4. Hydrochloric acid produces a higher concentration of H⁺ ions than ethanoic acid at the same concentration
5. The higher H⁺ ion concentration means more frequent collisions with sodium carbonate particles, so the reaction is faster

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](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/a-student-adds-sodium-carbonate-powder-81034e50) · Published by Druglandscape Ltd.