Conversion of Ethanol to Ethene by the action of concentrated sulphuric acid involves:

1. Dehydration
2. Dehydrogenation
3. Dehydrohalogenation
4. Hydrolysis

Dehydration

Reason — Dehydration involves elimination of elements of water from alcohol. Conc. sulphuric acid act as dehydrating agent.

$\underset{\text{ ethyl alcohol}}{\text{C}$2\text{H}5\text{OH}} \xrightarrow[170\degree\text{C}]{\text{Conc. H}2\text{SO}4\text{[excess]}} \underset{ \text{ethene}}{\text{C}2\text{H}4} + \text{H}_2\text{O}\

The products formed are ethene and water.