# Explain what happens at each electrode when a voltaic cell is constructed using a magnesium half-cell (Mg²⁺/Mg, E° = −2.37 V) and a silver half-cell (Ag⁺/Ag, E° = +0.80 V), including identification of the anode and cathode and the direction of electron flow in the external circuit.

> IB DP Chemistry Standard Level (2023 syllabus) — R3.2 Electron transfer reactions · Explain · 4 marks

## Mark scheme (4 marks)

1. Magnesium electrode is the anode where oxidation occurs (Mg → Mg²⁺ + 2e⁻)
2. Silver electrode is the cathode where reduction occurs (Ag⁺ + e⁻ → Ag)
3. Electrons flow through the external circuit from the magnesium electrode (anode) to the silver electrode (cathode)
4. The magnesium electrode has the more negative (lower) standard electrode potential, so it has the greater tendency to be oxidised / acts as the stronger reducing agent, driving the spontaneous reaction

## Key terms

- [anode](https://www.gradenine.co.uk/glossary/anode)
- [cathode](https://www.gradenine.co.uk/glossary/cathode)
- [electron flow](https://www.gradenine.co.uk/glossary/electron-flow)
- [voltaic cell](https://www.gradenine.co.uk/glossary/voltaic-cell)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](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/explain-what-happens-at-each-electrode-15de0a92) · Published by Druglandscape Ltd.