# Explain why increasing the concentration of hydrochloric acid increases the rate of reaction between hydrochloric acid and zinc.

> AQA A-Level Chemistry (7405) — 3.1.5 Kinetics · Explain · 5 marks

> A student investigates the reaction between zinc granules and hydrochloric acid. She notices that when she uses a higher concentration of acid, hydrogen gas is produced much more quickly.

## Mark scheme (5 marks)

1. Higher concentration means more particles of hydrochloric acid (hydrogen ions / HCl molecules) in the same volume
2. Particles collide more frequently / there are more collisions per second
3. More collisions between acid particles and zinc particles (collision between reactant particles)
4. More collisions have (at least) the activation energy / sufficient energy to react
5. Therefore more successful collisions per second, so the rate of reaction increases

## Key terms

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

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-increasing-the-concentration-of-09f65385) · Published by Druglandscape Ltd.