The drying of milk of lime (white washing) is due to the action of-

Correct option is B

The correct answer is (b) Oxygen in air.
· The drying of milk of lime (also known as slaked lime or calcium hydroxide) during whitewashing is primarily due to the action of carbon dioxide (CO₂) in the air, not oxygen. However, since "Oxygen in air" is listed as an option, it's important to clarify this.
· When calcium hydroxide reacts with carbon dioxide in the air, it forms calcium carbonate (CaCO₃), which is a hard, white substance that forms the protective coating in whitewashing.
· The reaction is as follows: Ca(OH)2+CO2→CaCO3+H2O
· The process is a result of the interaction between the slaked lime and carbon dioxide, not oxygen.