# Explain how electrolysis of molten lead(II) bromide produces lead and bromine, identifying which species is oxidised and which is reduced, and stating at which electrode each process occurs.

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

## Mark scheme (4 marks)

1. Pb²⁺ ions migrate to the cathode (negative electrode) and are reduced by gaining electrons to form lead metal.
2. Br⁻ ions migrate to the anode (positive electrode) and are oxidised by losing electrons to form bromine.
3. The lead(II) bromide must be molten (or dissolved) so that the ions are free to move and carry the current.
4. An external power source (direct current supply) drives the non-spontaneous reaction by forcing electron flow, distinguishing electrolysis from a spontaneous voltaic cell.

## Key terms

- [electrolysis](https://www.gradenine.co.uk/glossary/electrolysis)
- [molten](https://www.gradenine.co.uk/glossary/molten)

## 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)
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