Step 1: Reaction of ethanol with conc. H\(_2\)SO\(_4\).
Concentrated sulphuric acid acts as a dehydrating agent.
Step 2: Dehydration of ethanol.
On heating ethanol at about \(443K\), it loses water and forms ethene.
\[
CH_3CH_2OH \xrightarrow{conc.\,H_2SO_4,\,443K} CH_2=CH_2 + H_2O
\]
Step 3: Identify product.
The product is ethene \(C_2H_4\).
Final Answer:
\[
\boxed{C_2H_4}
\]