A volatile acid X is formed when sodium chloride reacts with concentrated sulphuric acid. Name this volatile acid.

The correct option is B

Hydrochloric acid

Concentrated sulphuric acid has a high boiling point (${338}^0$C) and so, it is considered to be a non-volatile acid. It is, therefore, used for preparing volatile acids like hydrochloric acid, nitric acid and acetic acid from their salts by double decomposition.

Sodium chloride reacts with concentrated sulphuric acid to form sodium bisulphate and hydrochloric acid.

$\underset{Saltofvolatileacid}{NaCI}+\underset{conc.}{H_{2}S{O}_4}\to \underset{acidsalt}{NaHS{O}_4}+\underset{volatileacid}{HCI}$