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 :
1. First, let’s verify Statement-I:
– Rainfall is indeed one of the major causes of weathering of rocks
– This statement is correct as water is a key agent of both mechanical and chemical weathering
2. Let’s check Statement-II:
– Rain water does contain dissolved carbon dioxide (CO2)
– When CO2 dissolves in water, it forms carbonic acid (H2CO3)
– This carbonic acid reacts with minerals in rocks, causing chemical weathering
– Statement-II is correct and helps explain Statement-I
3. Let’s examine Statement-III:
– Rain water does contain dissolved atmospheric oxygen
– Oxygen in rainwater can oxidize minerals, especially those containing iron
– This oxidation process contributes to chemical weathering
– Statement-III is also correct and helps explain Statement-I
4. Analyzing the relationships:
– Both Statements II and III are factually correct
– Both CO2 and O2 in rainwater contribute to chemical weathering of rocks
– Therefore, both statements help explain the weathering process mentioned in Statement-I
Looking at the given options, the answer would be (a): Both Statement-II and Statement-III are correct and both of them explain Statement-I.
