Q. Consider the following statements:
Statement – 1: Rainfall is one of the reasons for weathering of rocks.
Statement – 2: Rain water contains carbon dioxide in solution.
Statement – 3: Rain water contains atmospheric oxygen.
Which one of the following is correct in respect of the above statements?
Exp) Option a is the correct answer.
Weathering is the action of elements of weather and climate over earth materials. There are three major groups of weathering processes: (i) chemical; (ii) physical or mechanical; (iii) biological.
Statement I is correct: The chemical weathering processes act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and/or soil water and other acids. Water and air (oxygen and carbon dioxide) along with heat must be present to speed up all chemical reactions. Water from rainfall is one of the reasons for weathering rocks.
Statement II is correct: Normal rain has a pH of approximately 5.6, making it slightly acidic due to the dissolution of carbon dioxide (CO2), which forms weak carbonic acid. Thus, Statement II is correct and explains statement I.
Statement III is correct: During rain, oxygen concentrations in rain drops tend to rise as rain drops saturate with oxygen as they fall. Thus, Rainwater contains atmospheric oxygen.
Therefore, the rainfall supplies water, CO2, and oxygen facilitating the chemical weathering of rocks.
Statement II and Statement III are both correct and explain statement I.
