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✓ Correct
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
Explanation
Rainfall is indeed a key agent of chemical weathering. Rain water absorbs atmospheric carbon dioxide forming weak carbonic acid, which dissolves carbonate rocks (carbonation). Rain water also contains dissolved atmospheric oxygen, which causes oxidation of minerals (especially iron-bearing minerals), leading to chemical breakdown of rocks. Therefore, both Statements II and III are correct and both explain Statement-I, as both dissolved CO2 (causing carbonation) and dissolved O2 (causing oxidation) contribute to chemical weathering of rocks by rainwater.
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