Question

Why does dry HCI gas not change the color of the dry litmus papaer?

Answer 1

Dry HCL does not contain any hydrogen ions in it , so it does not show acidic behaviour . Dry HCl gas does not change the colour of a dry litmus paper as it has no hydrogen ions [H+ (aq)ions] in it .

Answer 2

We know that the colour of litmus paper is changed by H + ions because of acid.

Dry HCL it does not dissociate to give H+ ions.

Acids dissociate to give ions only in the aqueous solution.

In this HCL is not in aqueous form nor litmus paper is wet, so the colour of litmus paper does not change.