Question

Why is HCl gas unable to change the colour of a dry blue litmus paper? What happens if the litmus paper is moistened?
PLZ ANSWER FAST I NEED IT FOR MY ASSIGNMENT

Answer 1

It is because HCl gas is dry and there is no movement of ions in it. When litmus paper is moistened the gas becomes wet again and changes its colour.

Answer 2

Hello Dear !
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Hcl gas gives H+ ions only in aqueous solution  so it will not split into H+ + Cl- in the dry litmus paper no reaction occur 

With wet litmus paper water acts as a carrier for  splitting the Hcl into H+ + Cl-
Then reaction occurs and turn the blue litmus into red 
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