Question

Hydrogen chloride gas is dried by using :

• A. Calcium oxide
• B. Phosphorus pentoxide
• C. Calcium chloride
• D. Conc. sulphuric acid

Answer 1

The correct option is D

Conc. sulphuric acid

Explanation for correct option:

(D) Conc. Sulphuric acid:

The hydrogen chloride $\left(g\right)$ is dried by:

• The dehydrating agents are the agents which absorb the water molecules from the atmosphere and makes the substance dehydrated and dry it out.
• Concentrated sulphuric acid is a good drying agent as it has high affinity for water.
• $H_{2}S{O}_4$ is hygroscopic in nature i.e., water absorbing in nature.
• $H_{2}S{O}_4$ is therefore used to dry hydrogen chloride gas.
• Therefore, option (D) conc. sulphuric acid is correct.

Explanation for incorrect option:

(A) Calcium oxide:

• Calcium oxide cannot be used to dry hydrogen chloride gas as they will react to form calcium chloride and water.

(B) Phosphorous pentoxide:

• Phosphorous pentoxide reacts with hydrogen chloride gas to form phosphoryl chloride, so it cannot be used as a drying agent.

(C) Calcium chloride:

• Calcium chloride does not dry hydrogen chloride gas, so it cannot be used as drying agent.