# A student constructs an electrochemical cell using a silver half-cell (Ag⁺(aq)/Ag(s)) and a nickel half-cell (Ni²⁺(aq)/Ni(s)) connected by a salt bridge. The standard electrode potential of the silver half-cell is +0.80 V and that of the nickel half-cell is −0.25 V. Explain how the cell produces a voltage, identifying which electrode acts as the anode and which acts as the cathode, and describe the role of the salt bridge.

> Edexcel A-Level Chemistry (9CH0) — 14.1 Electrode potentials and electrochemical cells · Explain · 5 marks

> Standard electrode potentials: Ag⁺(aq) + e⁻ → Ag(s), E° = +0.80 V; Ni²⁺(aq) + 2e⁻ → Ni(s), E° = −0.25 V

## Mark scheme (5 marks)

1. The nickel electrode is the anode (negative electrode) because nickel is oxidised / loses electrons
2. The silver electrode is the cathode (positive electrode) because silver ions are reduced / gain electrons
3. The cell produces a voltage / EMF because there is a difference in electrode potentials between the two half-cells (accept: the more negative half-cell drives electrons towards the more positive half-cell)
4. Electrons flow through the external circuit from the nickel (anode) to the silver (cathode)
5. The salt bridge completes the circuit by allowing ions to flow between the two half-cells, maintaining electrical neutrality in each half-cell

## Key terms

- [standard electrode potential](https://www.gradenine.co.uk/glossary/standard-electrode-potential)
- [anode](https://www.gradenine.co.uk/glossary/anode)
- [cathode](https://www.gradenine.co.uk/glossary/cathode)
- [salt bridge](https://www.gradenine.co.uk/glossary/salt-bridge)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-constructs-an-electrochemical-cell-81d93972) · Published by Druglandscape Ltd.