Question

Name the gas obtained when rock salt reacts with concentrated sulphuric acid.

Answer 1

We know that sulphuric acid is highly acidic in nature and it reacts with different bases and forms the respective salts as the products. With some chemicals like metals, sulphuric acid produces a neutral gas as the product.

Complete answer:
In case of dehydration reaction water forms as one of the products. Concentrated sulphuric acid is a hygroscopic substance that has a high affinity for water molecules, so the presence of sulphuric acid with the heat on the reactant side in reaction indicates dehydration reaction. The presence of only sulphuric acid, no heat can lead to the oxidation reaction where the sulphuric acid acts as an oxidizing agent hence causing the oxidation of a species.
Sulphuric acid is a very strong acid in nature and going to react with all types of bases and forms respective salts at the same time sulphuric acid is going to react with few active metals and forms a neutral gas as the product. Concentrated sulphuric acid works as a dehydrating agent, so it discards water molecules from the compound and thus dehydrates the compound. These reactions are known as dehydration reactions and the substance which causes dehydration is known as a dehydrating agent.
Therefore, the gas obtained when rock salt reacts with concentrated sulphuric acid is hydrogen chloride gas.

Note:
Remember that the reaction of sodium chloride and sulphuric acid produces hydrochloric gas as a by-product. The gas hydrogen chloride escapes from the medium so the reaction cannot take place in a backward direction, and thus the reaction is irreversible.