A student adds a small piece of solid manganese(IV) oxide to a solution of hydrogen peroxide. The student notices that oxygen gas is produced much more quickly than when no manganese(IV) oxide is present. The manganese(IV) oxide remains unchanged at the end of the reaction. Explain how the manganese(IV) oxide increases the rate of this reaction.

Edexcel GCSE Chemistry (1CH0) — 7.1 Rates of reaction · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Manganese(IV) oxide is a catalyst.
It offers an alternative reaction pathway.
This pathway has a lower activation energy.
Consequently more collisions have enough energy, so the reaction rate increases.

Examiner tips

  • Use the word ‘catalyst’ first. Show the link: catalyst → lower activation energy → more successful collisions. Keep the answer concise and use the exact terms from the mark scheme.

Common mistakes

  • Saying the catalyst is ‘reactive’ instead of ‘catalytic’. Forgetting to mention the lower activation energy. Using vague phrases like ‘makes the reaction faster’ without explaining why.

Mark scheme (4 marks)

  1. Manganese(IV) oxide acts as a catalyst
  2. The catalyst provides a different (reaction) pathway / alternative route for the reaction
  3. This different pathway has a lower activation energy
  4. More (colliding) particles now have at least the activation energy, so there is a higher rate of successful collisions / the rate of reaction increases

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