# A student notices that a packet of crisps contains a small sachet labelled 'keep dry — contains silica gel, a desiccant catalyst for packaging reactions.' A chemistry teacher corrects this, explaining that silica gel is not a catalyst but that catalysts are used in many industrial processes to increase reaction rates. Explain how a solid catalyst increases the rate of a chemical reaction. In your answer, refer to activation energy and the Maxwell-Boltzmann distribution.

> Edexcel A-Level Chemistry (9CH0) — 9.1 Rates and the Maxwell-Boltzmann distribution · Explain · 5 marks

> Catalysts are widely used in industry to increase the rate of chemical reactions without being used up in the reaction. The Maxwell-Boltzmann distribution shows the spread of energies of particles in a reaction mixture at a given temperature.

## Mark scheme (5 marks)

1. A catalyst provides an alternative reaction pathway
2. The alternative pathway has a lower activation energy
3. A greater proportion / more particles have energy greater than or equal to the (new, lower) activation energy
4. Reference to the Maxwell-Boltzmann distribution: the area under the curve to the right of the (lower) activation energy is larger
5. Therefore more successful collisions per unit time occur, increasing the rate of reaction

## Key terms

- [activation energy](https://www.gradenine.co.uk/glossary/activation-energy)
- [Maxwell-Boltzmann distribution](https://www.gradenine.co.uk/glossary/maxwell-boltzmann-distribution)
- [catalyst](https://www.gradenine.co.uk/glossary/catalyst)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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-notices-that-a-packet-5f032a1f) · Published by Druglandscape Ltd.