# A student carries out two reactions. In Reaction A, zinc powder is added to dilute sulfuric acid at room temperature. In Reaction B, a large piece of zinc is added to the same volume of dilute sulfuric acid at the same temperature. The student notices that Reaction A produces bubbles much more quickly than Reaction B. Explain why Reaction A has a faster rate of reaction than Reaction B, and describe one other change the student could make to increase the rate of Reaction A even further, explaining how it works.

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

> Zinc reacts with dilute sulfuric acid to produce zinc sulfate and hydrogen gas. The rate of reaction can be affected by several factors.

## Mark scheme (5 marks)

1. Zinc powder has a greater surface area (to volume ratio) than a large piece of zinc
2. There are more exposed reacting particles / more zinc particles in contact with the acid
3. This leads to more frequent successful collisions, so the rate of reaction increases
4. A valid change is stated, e.g. increase the temperature, increase the concentration of sulfuric acid, or add a catalyst
5. Correct explanation linked to the chosen change, e.g. higher temperature gives particles more kinetic energy so more particles have at least the activation energy and collisions are more frequent; OR higher concentration means particles are closer together so collisions are more frequent; OR a catalyst provides a different reaction pathway with a lower activation energy

## 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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-carries-out-two-reactions-bffc2eeb) · Published by Druglandscape Ltd.