Question

why does the dry HCL gas do not change the colour of the dry Litmus Paper

Answer 1

Dry Hcl gas does not contain any hydrogen ions in it, so it does not show acidic behaviour. Dry HCl gas does not change the colour of dry litmus paperas it has no hydrogen ions [H+(aq) ions] in it. ... Because Acid needs water to create its effect.

Answer 2

Dry hcl gas does not ionize to produce h+ ions. Hence, it does not show acidic properties and therefore  does not change the colour of dry litmus paper.

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