Question

Dry HCI gas does not change the colour of dry blue litmus paper. Give reasons.

Answer 1

Because it does not have hydronium ions...which show acidic nature that is turn blue litmus red....so due to absence of hydronium ions it does not turn blue litmus red....

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.