# Bromine can be extracted from sea water. Explain how bromine is obtained from sea water using chlorine, and explain why chlorine is able to displace bromine from the solution.

> OCR A-Level Chemistry B: Salters (H433) — ES Elements from the sea · Explain · 5 marks

> Sea water contains bromide ions at low concentrations. The chemical industry extracts bromine from sea water on a large scale by reacting the sea water with chlorine gas.

## Mark scheme (5 marks)

1. Chlorine is added to / bubbled through sea water containing bromide ions
2. A displacement reaction occurs, producing bromine / bromide ions are oxidised to bromine
3. Chlorine is more reactive than bromine
4. Chlorine is higher in the halogen reactivity series / halogens become less reactive going down Group 7
5. A more reactive halogen can displace a less reactive halogen from a solution of its salt / chlorine can gain electrons more easily than bromine so it displaces bromide ions

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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