# A student adds a small piece of manganese(IV) oxide to a solution of hydrogen peroxide. Bubbles of gas are produced rapidly, but when the reaction is complete, the mass of manganese(IV) oxide is unchanged. Explain the role of manganese(IV) oxide in this reaction and describe how the rate of bubble production would change over time as the reaction proceeds.

> Cambridge International IGCSE Chemistry (0620) — 6.2 Rate of reaction · Explain · 4 marks

## Mark scheme (4 marks)

1. Manganese(IV) oxide acts as a catalyst
2. A catalyst increases the rate of reaction without being used up / without being chemically changed
3. The rate of bubble production decreases over time
4. Because the concentration of hydrogen peroxide decreases as it is used up

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