Zinc powder is added to silver nitrate solution. The zinc displaces silver from the solution. In this reaction, zinc atoms lose electrons and silver ions gain electrons. Explain why this reaction is described as a redox reaction, and identify which substance is oxidised and which is reduced.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
When zinc powder is added to silver nitrate solution, a grey coating of silver metal forms on the zinc and the solution becomes colourless. The overall reaction can be represented as: Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag
Model answer (5 marks)
The reaction is a redox reaction because oxidation and reduction occur at the same time. Zinc atoms lose electrons (oxidation) and silver ions gain electrons (reduction). Zinc is therefore the reducing agent, donating electrons to silver ions. Silver ions are the oxidising agent, accepting electrons from zinc.
Examiner tips
- State that oxidation and reduction happen simultaneously
- Identify zinc as oxidised and silver ions as reduced
- Explain zinc as reducing agent and silver ions as oxidising agent
- Use correct terminology: oxidised, reduced, reducing agent, oxidising agent
Common mistakes
- Saying only one substance is oxidised or reduced
- Confusing oxidising agent with the substance that is oxidised
- Using ‘reduced’ for zinc instead of ‘oxidised’
Mark scheme (5 marks)
- Oxidation and reduction occur simultaneously (in the same reaction)
- Zinc is oxidised because it loses electrons
- Silver ions are reduced because they gain electrons
- Zinc is the reducing agent because it causes the reduction of silver ions (by donating electrons to them)
- Silver nitrate / silver ions act as the oxidising agent because they cause the oxidation of zinc (by accepting electrons from zinc)
Key terms in this question
Related
- All WJEC A-Level Chemistry (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Redox questions
- Iron can be extracted from iron oxide by heating it with carbon. In this reactio…
- A student uses paper chromatography to investigate whether a food dye is a pure …
- Crude oil is separated into useful products using fractional distillation. Expla…
- Magnesium ribbon is added to copper sulfate solution. The magnesium displaces co…