In the elimination reaction of ethyl alcohol to ethene  ____________

When ethanol reacts with concentrated sulphuric acid at 443K,  ethanol gets converted to ethene by losing a water molecule. Since a water molecule is lost during the reaction, sulphuric acid acts as a dehydrating agent which removes the excess water formed during the reaction.
The reaction is:
$C{H}_3-C{H}_{2}OH\underset{H_{2}S{O}_4}{\overset{Hotconc.}{\to }}C{H}_2=C{H}_2+H_{2}O$