Copper wire is placed into a solution of silver nitrate. Over time, the copper wire becomes coated with silver metal and the solution turns blue as copper(II) ions form. Explain why this reaction is a redox reaction.

Cambridge International IGCSE Chemistry (0620) — 6.4 Redox · Explain · 4 marks · View as Markdown

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

Copper wire is placed into a solution of silver nitrate. Over time, the copper wire becomes coated with silver metal and the solution turns blue as copper(II) ions form.

Model answer (4 marks)

Copper atoms lose electrons (Cu → Cu²⁺ + 2e⁻), so copper is oxidised.
Silver ions gain electrons (Ag⁺ + e⁻ → Ag), so silver is reduced.
The electrons released by copper are transferred to silver ions.
Thus both oxidation and reduction occur simultaneously, making this a redox reaction.

Examiner tips

  • Show the half‑reactions and the electron transfer.
  • Use the terms ‘oxidised’ and ‘reduced’ and the ion symbols Cu²⁺ and Ag⁺.
  • Explain that electrons move from copper to silver.
  • Mention that the colour change is due to Cu²⁺ ions in solution.

Common mistakes

  • Forgetting to state that copper is oxidised or silver is reduced.
  • Using ‘copper ions’ instead of Cu²⁺ or ‘silver metal’ instead of Ag⁺.
  • Not showing that electrons are transferred between the two species.

Mark scheme (4 marks)

  1. Copper atoms lose electrons / copper is oxidised
  2. Copper atoms form copper(II) ions / Cu → Cu²⁺
  3. Silver ions gain electrons / silver ions are reduced
  4. Both oxidation and reduction occur simultaneously / electrons are transferred from copper to silver ions

Key terms in this question

redox

Related

More Redox questions

▶ Try answering this question with AI marking (free) →