A student adds a piece of zinc to iron sulfate solution. No visible reaction occurs when zinc is added to silver nitrate solution. Explain what the student would observe when zinc is added to iron sulfate solution, and why no reaction occurs with silver nitrate solution.

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).

Zinc, iron, and silver can all be placed in the reactivity series. Zinc is more reactive than iron. Silver is more reactive than zinc.

Model answer (4 marks)

Zinc displaces iron from iron(II) sulfate because zinc is higher in the reactivity series. A grey‑black solid of iron is deposited on the zinc surface and the solution becomes colourless as the iron(II) ions are removed.

No reaction occurs with silver nitrate because silver is more reactive than zinc. A more reactive metal can only displace a less reactive metal from its compound, so zinc cannot displace silver from AgNO₃.

Examiner tips

  • Use the phrase ‘displaces’ to show displacement reaction. Mention the colour change of the solution. State the order of reactivity for the two reactions.
  • common_mistakes
  • :
  • Saying zinc dissolves instead of iron deposits. Claiming silver reacts with zinc. Using vague terms like ‘reacts’ without specifying displacement.

Mark scheme (4 marks)

  1. Zinc displaces iron from iron sulfate solution because zinc is more reactive than iron
  2. A grey/dark solid (iron) forms on the surface of the zinc / the solution loses colour / the zinc dissolves
  3. No reaction occurs with silver nitrate because silver is more reactive than zinc
  4. A more reactive element can only displace a less reactive element from its compound / zinc is less reactive than silver so cannot displace it

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