# Explain why increasing the concentration of hydrochloric acid increases the rate at which it reacts with zinc metal.

> OCR GCSE Chemistry A: Gateway Science (J248) — C5.1 Monitoring chemical reactions · Explain · 4 marks

> A student investigating rate of reaction uses two different concentrations of hydrochloric acid with excess zinc granules. She notices that the more concentrated acid produces gas much more quickly than the dilute acid.

## Mark scheme (4 marks)

1. Increasing concentration means reacting particles are closer together
2. Particles collide more often / there is a higher frequency of collisions
3. There is a higher rate of successful collisions
4. Therefore the rate of reaction increases

## Key terms

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

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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