Question

A is a gas which on dissolving in water forms an acid B. This acid on reaction with calcium hydroxide gives C and water. Identify A, B and C.

• A. A- Carbon dioxide, B- Carbonic acid, C- Calcium carbonate
• B. A- Carbon monoxide, B- Carbonic acid, C- Calcium oxide
• C. A- Oxygen, B- Sodium sulphate, C- Sodium carbonate
• D. A- Carbon dioxide, B- Carbonic acid, C- Calcium chloride

Answer 1

The correct option is A A- Carbon dioxide, B- Carbonic acid, C- Calcium carbonate

Carbon dioxide is a gas which forms carbonic acid when dissolved in water. The reaction involved is:

${\text{CO}}_2+{\text{H}}_2\text{O}\rightleftharpoons {\text{H}}_2{\text{CO}}_3$

Carbonic acid, on further reaction with calcium hydroxide gives calcium carbonate and water. The reaction involved is:

${\text{H}}_2{\text{CO}}_3+{\text{Ca(OH)}}_2\to {\text{CaCO}}_3+2{\text{H}}_2\text{O}$

So, A is carbon dioxide, B is carbonic acid and C is calcium carbonate.