Zinc, copper and magnesium are all metals. A student places a piece of magnesium into copper sulfate solution and observes a reaction. Explain why this reaction occurs and predict what would happen if zinc were used instead of magnesium.

AQA GCSE Chemistry (8462) — 4.4.1 Reactivity of metals · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Magnesium is more reactive than copper.
A more reactive metal can displace a less reactive metal from its compound, so magnesium displaces copper from copper(II) sulfate.
Zinc is less reactive than magnesium but more reactive than copper, so zinc would also displace copper from copper(II) sulfate.
The reaction with zinc would be slower or less vigorous than with magnesium.

Examiner tips

  • Use the displacement‑reaction concept; mention reactivity series.
  • Show the order Mg > Zn > Cu to justify predictions.
  • Explain that rate depends on relative reactivity.

Common mistakes

  • Confusing the order of the reactivity series; writing Zn > Mg > Cu.
  • Failing to mention that the reaction with zinc is slower.

Mark scheme (4 marks)

  1. Magnesium is more reactive than copper
  2. A more reactive metal displaces a less reactive metal from its compound / magnesium displaces copper from copper sulfate
  3. Zinc is less reactive than magnesium (but more reactive than copper), so zinc would also displace copper from copper sulfate
  4. The reaction with zinc would be slower / less vigorous than with magnesium

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