Question

The drying agent for chlorine gas is ____?

Answer 1

Drying agents have a tendency to collect moisture in the form of water vapours. A drying agent is added to a specific gas or solid in order to remove the moisture mixed with it or absorbed by it so as to get a completely pure substance.

Complete answer:
A large variety of compounds are used as drying agents for different gases and solids. Their purpose is to remove moisture present in the substance. Some common drying agents are concentrated sulphuric acid, phosphorus pentoxide and calcium oxide.
These chemical species have a high affinity for water molecules and absorb all the moisture present in a reaction flask so as to remove water from it. The drying agents are also referred to as dehydrating agents.
Concentrated sulphuric acid is essentially used in drying chlorine gas. Before the chlorine gas is compressed a stream of dilute acid (combination of sulphuric acid and chlorine gas) is created which contains saturated chlorine gas. In the final drying tower, the sulphuric acid vapours are segregated from the chlorine gas.
Hence, concentrated sulphuric acid is the suitable drying agent for chlorine gas.

Note:
The drying agent of any material is selected keeping in mind the nature of the material being dried and the nature of the material being used as a drying agent. If the substance is capable of reacting with a drying agent or the gas can get adsorbed onto a drying agent which is solid, then such a drying agent is not suitable for the particular substance.