Question

Hydrogen chloride gas is highly soluble in water and is dried by:

• A. Anhydrous calcium chloride
• B. Phosphorous pentaoxide
• C. Quick lime
• D. Concentrated sulphuric acid

Answer 1

The correct option is D

Concentrated sulphuric acid

Explanation for the correct option:

(D) Concentrated sulphuric acid

Hydrogen chloride gas is highly soluble in water and is dried by bubbling the gas through concentrated sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$.

Explanation for the incorrect option:

(A) Anhydrous calcium chloride

Hydrogen chloride gas is not dried by anhydrous calcium chloride because it reacts with $\mathrm{HCl}$.

Calcium is present above the Hydrogen in the activity series of metals so the reaction will be destroyed.

(B) Phosphorous pentaoxide

Hydrogen chloride gas is not dried by phosphorous pentaoxide because it reacts with $\mathrm{HCl}$.

$2{\mathrm{P}}_2{\mathrm{O}}_5\left(\mathrm{s}\right)+3\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{POCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{HPO}}_3\left(\mathrm{aq}\right)$

(C) Quick lime

Hydrogen chloride gas is not dried by quick lime because it reacts with $\mathrm{HCl}$.

$\mathrm{CaO}\left(\mathrm{s}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{CaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, the correct option is (D), Hydrogen chloride gas is highly soluble in water and is dried by concentrated sulphuric acid.