Copper, zinc and magnesium are three metals found in the reactivity series. A student places a strip of zinc into a solution of copper sulfate and observes a change. Explain what the student observes and why this reaction occurs, using the concept of displacement.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The reactivity series, in order from most reactive to least reactive, includes: magnesium, zinc, copper.
Model answer (4 marks)
Zinc is more reactive than copper.
A more reactive metal displaces a less reactive metal from its compound.
When the zinc strip is added to copper(II) sulfate, zinc displaces copper:
Zn(s)+CuSO₄(aq)→ZnSO₄(aq)+Cu(s).
A reddish‑orange solid of copper is deposited on the zinc strip (or appears in solution).
The blue colour of the copper(II) sulfate solution fades as Cu²⁺ ions are removed.
A more reactive metal displaces a less reactive metal from its compound.
When the zinc strip is added to copper(II) sulfate, zinc displaces copper:
Zn(s)+CuSO₄(aq)→ZnSO₄(aq)+Cu(s).
A reddish‑orange solid of copper is deposited on the zinc strip (or appears in solution).
The blue colour of the copper(II) sulfate solution fades as Cu²⁺ ions are removed.
Examiner tips
- State the reactivity order first. Explain displacement using the phrase "more reactive displaces less reactive". Describe the copper deposit and colour change. Show the balanced equation if space allows.
Common mistakes
- Confusing the direction of displacement (copper displacing zinc). Failing to mention the colour change of the solution. Using vague terms like "metal reacts" without specifying displacement.
Mark scheme (4 marks)
- Zinc is more reactive than copper (or copper is less reactive than zinc)
- A more reactive element displaces a less reactive element from its compound
- A reddish/orange-brown solid (copper) is deposited on the zinc strip (or forms in solution)
- The blue colour of the copper sulfate solution fades (as copper ions are removed from solution)
Key terms in this question
reactivity series · displacement · copper sulfate
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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