# A student carries out electrolysis of brine (concentrated sodium chloride solution) using inert electrodes. Describe what is produced at each electrode and explain why these products form.

> OCR GCSE Chemistry A: Gateway Science (J248) — C3.4 Electrolysis · Describe · 4 marks

> Brine is a concentrated solution of sodium chloride in water. It is an important industrial feedstock and its electrolysis produces useful products at both electrodes.

## Mark scheme (4 marks)

1. Chlorine gas is produced at the anode (positive electrode)
2. Chloride ions are negatively charged (anions) and move to the anode where they lose electrons (oxidation), forming chlorine gas
3. Hydrogen gas is produced at the cathode (negative electrode)
4. Hydrogen ions (H⁺) from water are positively charged (cations) and move to the cathode where they gain electrons (reduction), forming hydrogen gas, because sodium is more reactive than hydrogen

## Key terms

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

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-carries-out-electrolysis-of-8fafe1c1) · Published by Druglandscape Ltd.