# Ethene can react with steam in the presence of a phosphoric acid catalyst to produce ethanol. Explain why ethene is described as an unsaturated hydrocarbon and state the type of reaction that occurs when ethene reacts with steam.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.4 Alkenes · Explain · 4 marks

> Ethene has the molecular formula C₂H₄. It reacts with steam at high temperature and pressure in the presence of a phosphoric acid catalyst to form ethanol, C₂H₅OH.

## Mark scheme (4 marks)

1. Ethene is a hydrocarbon because it contains hydrogen and carbon atoms only
2. Ethene is unsaturated because it contains a carbon–carbon double bond (C=C)
3. The double bond allows ethene to react / the double bond opens / not all carbon valencies satisfied by hydrogen
4. The reaction with steam is an addition reaction

## Key terms

- [unsaturated](https://www.gradenine.co.uk/glossary/unsaturated)
- [hydrocarbon](https://www.gradenine.co.uk/glossary/hydrocarbon)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/ethene-can-react-with-steam-in-f0ed6d47) · Published by Druglandscape Ltd.