Question

Give reason:

Dry HCl gas does not turn blue litmus red whereas dilute hydrochloric acid does.

Answer 1

1. Dry hydrogen chloride gas does not dissociate in the absence of water. Hence, it does not turn blue litmus to red. So, dry hydrogen chloride gas is not acidic.
2. The HCl (hydrochloric acid) dissociates in the presence of water. Hence, it turns blue litmus to red. So, HCl (Hydrochloric acid) is acidic. The dissociation will be as follows:

\[\ce{HCl + H2O -> H2O+ + Cl-}\]