# Manganese(IV) oxide is used as a catalyst in the decomposition of hydrogen peroxide solution to produce water and oxygen. A student investigates how changing the mass of manganese(IV) oxide added affects the rate of this reaction. Explain how manganese(IV) oxide acts as a catalyst in this reaction and describe what happens to the mass of manganese(IV) oxide at the end of the reaction.

> OCR A-Level Chemistry B: Salters (H433) — 5.3 Transition elements · Explain · 5 marks

> Hydrogen peroxide solution decomposes slowly at room temperature. Adding manganese(IV) oxide greatly speeds up this decomposition. The reaction can be represented as: 2H₂O₂(aq) → 2H₂O(l) + O₂(g)

## Mark scheme (5 marks)

1. A catalyst provides a different reaction pathway / alternative reaction pathway
2. The alternative pathway has a lower activation energy
3. A greater proportion of particles have energy greater than or equal to the (lower) activation energy
4. The manganese(IV) oxide is not used up / its mass remains the same at the end of the reaction
5. Therefore increasing the mass of manganese(IV) oxide increases the rate of reaction because there is more surface area / more active sites for the reaction to occur

## Key terms

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

## 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/manganese-iv-oxide-is-used-as-a-3a30b7a4) · Published by Druglandscape Ltd.