Explain why zinc can displace copper from copper sulfate solution, but copper cannot displace zinc from zinc sulfate solution.

Cambridge International IGCSE Chemistry (0620) — 9.4 Reactivity series · Explain · 4 marks · View as Markdown

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

A student places a piece of zinc metal into copper sulfate solution and observes that the blue colour fades and a reddish-brown solid forms. When the experiment is repeated using copper metal in zinc sulfate solution, no change is observed.

Model answer (4 marks)

Zinc is higher in the reactivity series than copper.
A metal higher in the series can displace a metal lower in the series from its salt solution.
Therefore zinc displaces copper from copper(II) sulfate.
Copper is lower in the series, so it cannot displace zinc from zinc sulfate, and no reaction occurs.

Examiner tips

  • State the position of zinc and copper in the reactivity series. Explain the displacement rule. Show the direction of the reaction. Mention that no reaction occurs in the reverse case.

Common mistakes

  • Confusing the order of the reactivity series. Forgetting to mention that no reaction occurs when copper is placed in zinc sulfate. Using vague terms like "more reactive" without linking to the series.

Mark scheme (4 marks)

  1. Zinc is higher/more reactive than copper (in the reactivity series)
  2. A more reactive metal displaces a less reactive metal from its salt solution
  3. Copper is less reactive than zinc / copper cannot displace zinc because copper is lower in the reactivity series
  4. Therefore no reaction occurs when copper is placed in zinc sulfate solution

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