Answer these questions selecting the appropriate option given below:

Assertion (A): Copper becomes dull in moist air.

Reason (R): Copper is coated by a thin film of its basic copper carbonate formed in moist air.

Both A and R are true and R is the correct explanation of A.

The correct answer is option 1. Both A and R are true and R is the correct explanation of A.

Assertion (A):  Copper becomes dull in moist air. - This statement is true. When copper is exposed to moist air (containing water vapor and carbon dioxide), it undergoes a chemical reaction.

Reason (R):  Copper is coated by a thin film of its basic copper carbonate formed in moist air. - This statement is also true. The reaction between copper, oxygen, water vapor, and carbon dioxide in moist air leads to the formation of a green-colored layer of copper carbonate (usually a mixture of CuCO₃ and Cu(OH)â‚‚) on the surface.

The film of copper carbonate is not as reflective as the pure copper surface. Light interacts differently with this layer, causing the copper to lose its shine and appear dull.

Therefore, both the assertion and the reason are true, and the reason explains why copper becomes dull in moist air.