Question

Dry HCl gas does not change the colour of dry blue litmus paper. Why?

Why does dry HCl gas not change the colour of dry litmus paper?

Answer 1

Dry HCl gas does not release hydrogen ions (H⁺ ions) in the absence of water. An acid shows its acidic behaviour and changes the colour of litmus paper only when it releases H⁺ ions. Since both the HCl gas and the litmus paper are dry, no water is present for dissociation. Therefore, dry HCl gas does not show acidic properties and does not change the colour of dry litmus paper.