Consider the following statements

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

Explanation

The correct answer is (a). Here’s why: Statement-I is correct: Rainfall is indeed a major reason for weathering of rocks. Water physically weakens rocks through processes like erosion and can dissolve some minerals. Statement-II is correct: Rainwater does contain dissolved carbon dioxide from the atmosphere. This forms a weak carbonic acid solution. Statement-III is correct: Rainwater also absorbs some atmospheric oxygen when it falls. How Statements II and III explain Statement I: Carbonic acid: Rainwater with dissolved carbon dioxide (CO2) becomes weakly acidic (H2CO3). This weak acid can slowly dissolve certain minerals in rocks, contributing to chemical weathering. Oxygen: Dissolved oxygen in rainwater can react with some minerals in rocks, promoting oxidation, another form of chemical weathering. Therefore, both Statements II and III are correct, and they both contribute to explaining why rainfall weathers rocks (Statement I).