Question

Which of the following substances can be used for drying gases?
A. Calcium carbonate
B. Sodium carbonate
C. Sodium bicarbonate
D. Calcium oxide

Answer 1

Hint: The compound which can absorb moisture is used for drying gas. Calcium oxide has the power to absorb the moisture and dry the gas.

Complete Step by Step Answer:
Calcium oxide is an oxide of calcium, an alkaline earth metal. Calcium oxide has high basic properties. It is a basic gas. On treatment with water it forms calcium hydroxide which is highly basic hydroxide.
Calcium hydroxide has a strong power to absorb moisture from various other gases. Thus it is used from drying gases because calcium oxide easily absorbs moisture to form basic calcium hydroxide.
Thus the correct option is D.

Additional information: Limestone is a carbonate compound of calcium that is calcium carbonate. Calcium carbonate undergoes thermal decomposition in presence of heat to form calcium oxide along with carbon dioxide gas.
The reaction can be given as follows:
$CaC{{O}_{3}}\to CaO+C{{O}_{2}}$. In this reaction one mole of calcium carbonate is heated to form one mole of metal oxide ore that is calcium oxide along with carbon dioxide gas. On heating limestone or calcium carbonate decomposes to calcium oxide and carbon dioxide gas. In this reaction heat is needed, so it is an endothermic reaction.

Note: Calcium oxide is a basic oxide so, dry only basic gases. Other than gases it can also dry ether, alcohols etc.