With reference to whitewashing of walls using slaked lime, consider the following statements: 1. A shiny finish appears immediately after applying…

The correct option is

2 and 3 only

.

Explanation

Whitewashing involves the application of a solution of slaked lime (calcium hydroxide) on walls. This solution undergoes a chemical reaction with atmospheric gases to form a stable compound that provides a protective and decorative finish.

Statement-wise Analysis:

• Statement 1 is Incorrect: The shiny finish does not appear immediately upon application. The reaction between the applied solution and atmospheric gases is slow. It typically takes two to three days for the final layer to form and produce a shiny white finish.
• Statement 2 is Correct: The layer is formed by the reaction of calcium hydroxide [Ca(OH)₂] with carbon dioxide (CO₂) present in the air. This reaction produces calcium carbonate (CaCO₃) and water.
• Statement 3 is Correct: The chemical formula of the layer formed on the walls is calcium carbonate (CaCO₃). This is chemically identical to marble, which is a metamorphic rock composed primarily of recrystallized carbonate minerals, specifically calcium carbonate.

Key Takeaway:
The shiny finish on whitewashed walls is caused by the formation of Calcium Carbonate (CaCO₃), which results from the slow reaction of slaked lime with atmospheric carbon dioxide.