The dehydration of ethanol results in the formation of:

A chemical reaction that involves the loss of water from the reacting molecule or ion is known as dehydration. The dehydration of ethanol involves heating at about $170℃$in the presence of conc. sulphuric acid. Sulphuric acid acts as the dehydrating agent in the reaction. Ethene is obtained as the product.

A well-balanced reaction for the same is as follows:
${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} + {\mathrm{H}}_2{\mathrm{SO}}_4 \to {\mathrm{C}}_2{\mathrm{H}}_4 + {\mathrm{H}}_2\mathrm{O}$
Ethanol + Conc. Sulphuric Acid → Ethene + Water