# A student sets up an electrochemical cell using a zinc half-cell and a copper half-cell. The standard electrode potentials are: Zn²⁺/Zn = −0.76 V and Cu²⁺/Cu = +0.34 V. Explain which electrode acts as the negative electrode and why electrons flow in the direction they do through the external circuit.

> AQA A-Level Chemistry (7405) — 3.1.11 Electrode potentials and electrochemical cells (A-Level only) · Explain · 5 marks

> The cell is set up under standard conditions, with each half-cell containing a metal electrode in a 1.0 mol/dm³ solution of its metal ions. The two half-cells are connected by a salt bridge and an external wire.

## Mark scheme (5 marks)

1. Zinc has a more negative standard electrode potential than copper, so zinc is the negative electrode.
2. Zinc is oxidised at the negative electrode, losing electrons.
3. Electrons flow from the zinc electrode to the copper electrode through the external circuit.
4. Copper ions are reduced at the copper electrode, gaining the electrons.
5. The driving force for electron flow is the difference in standard electrode potentials between the two half-cells (the cell EMF).

## Key terms

- [standard electrode potential](https://www.gradenine.co.uk/glossary/standard-electrode-potential)
- [negative electrode](https://www.gradenine.co.uk/glossary/negative-electrode)
- [external circuit](https://www.gradenine.co.uk/glossary/external-circuit)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](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-sets-up-an-electrochemical-7eb05e21) · Published by Druglandscape Ltd.