Q. Consider the following statements:
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
Correct answer: (a) Both Statement-II and Statement-III are correct and both of them explain Statement-I
Question from UPSC Prelims 2024 GS Paper
Explanation:
Statement-I: Rainfall is one of the reasons for weathering of rocks.
This statement is correct. Rainfall is indeed a significant factor in rock weathering through various processes.
Statement-II: Rain water contains carbon dioxide in solution.
This statement is correct. As rainwater falls through the atmosphere, it absorbs carbon dioxide, forming a weak carbonic acid solution.
Statement-III: Rain water contains atmospheric oxygen.
This statement is also correct. Rainwater can dissolve atmospheric oxygen as it falls.
Now, let’s consider how these statements relate to each other:
1. Carbon dioxide in rainwater (Statement-II) contributes to chemical weathering. The carbonic acid formed can react with minerals in rocks, breaking them down over time.
2. Dissolved oxygen in rainwater (Statement-III) can also contribute to weathering, particularly through oxidation reactions with minerals containing iron.
3. Both the presence of carbon dioxide and oxygen in rainwater contribute to its ability to weather rocks, thus explaining Statement-I.