# A student investigates the rate of a reaction between marble chips (calcium carbonate) and hydrochloric acid. She carries out the experiment at 25 °C and then repeats it at 45 °C, keeping all other variables the same. Explain why the rate of reaction is faster at 45 °C than at 25 °C.

> OCR A-Level Chemistry B: Salters (H433) — 5.2 Energy · Explain · 5 marks

> Marble chips react with hydrochloric acid to produce carbon dioxide gas. The rate of reaction can be monitored by measuring the volume of gas collected over time.

## Mark scheme (5 marks)

1. At a higher temperature, particles have more kinetic energy
2. Particles move faster, so they collide more often / there is a greater frequency of collisions
3. A greater proportion of particles have energy greater than or equal to the activation energy
4. There is therefore a higher rate of successful collisions
5. Both the increased collision frequency AND the greater proportion of particles with activation energy contribute to the faster rate of reaction

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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/a-student-investigates-the-rate-of-428d7363) · Published by Druglandscape Ltd.