After 2 to 3 days of whitewashing of walls with a solution of slaked lime, which of the following compounds is produced that gives a shiny finish to the walls?

Correct option is D

The correct answer is:(D) Calcium carbonate

• When slaked lime (calcium hydroxide, Ca(OH)₂) is used for whitewashing, it reacts with carbon dioxide (CO₂) from the air over 2 to 3 days.
• The reaction produces calcium carbonate (CaCO₃), which is a white, crystalline compound that gives the walls a shiny and smooth finish. This process is called the carbonation of lime.

The reaction is as follows:

Ca(OH)2+CO2→CaCO3+H2O\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3 + \text{H}_2\text{O}Ca(OH)2​+CO2​→CaCO3​+H2​O

This calcium carbonate forms a protective, durable layer on the wall and gives it the desired shiny finish.

Information booster:

• Calcium hydroxide: This is the compound used in the initial whitewashing solution. It does not give the shiny finish but reacts with CO₂ to form calcium carbonate.
• Calcium dioxide: This is not a correct compound in this context. It may be confused with calcium oxide (quicklime), which reacts with water to form slaked lime, but it is not the product that provides the shiny finish.
• Calcium bicarbonate: Calcium bicarbonate is an unstable compound that forms when calcium hydroxide reacts with carbon dioxide in water. It decomposes back into calcium carbonate and carbon dioxide, so it does not give the shiny finish.