Dry hydrogen chloride gas does not turn blue litmus red whereas hydrochloric acid does. Give one reason.

(N/A) Dry hydrogen chloride gas does not contain $H^{+}$ ions. Acids exhibit acidic properties only in the presence of water because they dissociate to produce hydrogen ions $H^{+}(aq)$. Since dry $HCl$ gas lacks water,it cannot release $H^{+}$ ions,and therefore,it does not show acidic behavior or change the color of blue litmus paper.