# A student adds marble chips (calcium carbonate) to two separate acid solutions of equal concentration and volume. One acid is hydrochloric acid (a strong acid) and the other is ethanoic acid (a weak acid). The student observes that the marble chips react more vigorously with the hydrochloric acid. Explain why the reaction with hydrochloric acid is more vigorous than the reaction with ethanoic acid.

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

> Marble chips react with acids to produce carbon dioxide gas. A student investigates the reaction of marble chips with two different acids of equal concentration.

## Mark scheme (4 marks)

1. Hydrochloric acid is a strong acid that is completely ionised in aqueous solution
2. Ethanoic acid is a weak acid that is only partially ionised in aqueous solution
3. Hydrochloric acid therefore has a higher concentration of hydrogen ions (H⁺) in solution
4. A higher concentration of H⁺ ions causes a faster/more vigorous reaction with the marble chips

## 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/a-student-adds-marble-chips-calcium-4e7a404a) · Published by Druglandscape Ltd.