68th B.P.S.C. (Pre) 2023
Why does dry HCl gas not change the color of dry litmus paper?
aHCl gas acts as a dehydrating agent
bBlue litmus becomes dry in the presence of dry HCl gas
cNo H₃O⁺ ions are present. Litmus changes color only in the presence of H₃O⁺ ions✓ Correct
dMore than one of the above
eNone of the above
Explanation
Litmus paper changes color only in the presence of ions such as hydrogen (H⁺) or hydronium (H₃O⁺). HCl can produce these ions only in aqueous solution. Therefore, dry HCl gas does not change the colour of dry litmus paper.
general-science