Consider the following statements:

Question

Statement-I: Rainfall is one of the reasons for weathering of rocks.
Statement-II: Rain water contains carbon dioxide in solution.
Statement-III: Rain water contains atmospheric oxygen.

Which one of the following is correct in respect of the above statements?

(a) Both Statement-II and Statement-III are correct and both of them explain Statement-I
(b) Both Statement-II and Statement-III are correct, but only one of them explains Statement-I
(c) Only one of the Statements II and III is correct and that explains Statement-I
(d) Neither Statement-II nor Statement-III is correct

Answer 1

(b) Both Statement-II and Statement-III are correct, but only one of them explains Statement-I

Explanation:

• Statement-I: Rainfall is indeed one of the reasons for the weathering of rocks. Weathering is the process by which rocks are broken down into smaller pieces by physical, chemical, or biological processes. Rainfall contributes to chemical weathering by dissolving minerals and also to physical weathering by causing repeated wetting and drying cycles.

• Statement-II: Rainwater does contain carbon dioxide in solution. When rain falls through the atmosphere, it dissolves carbon dioxide to form weak carbonic acid. This acid can react with minerals in rocks, contributing to chemical weathering.

• Statement-III: Rainwater also contains atmospheric oxygen, but the presence of oxygen in rainwater is not a significant factor in the weathering of rocks compared to the presence of carbon dioxide.

Since both Statements II and III are correct, but only Statement II directly explains how rainwater contributes to the weathering of rocks, the correct option is (b) Both Statement-II and Statement-III are correct, but only one of them explains Statement-I.