निम्नलिखित कथनों पर विचार कीजिए :
- कथन-I: चट्टानों के अपक्षय के कारणों में से एक कारण वर्षा है ।
- कथन-II: वर्षा जल में घोल के रूप में कार्बन डाइऑक्साइड विद्यमान होता है ।
- कथन-III: वर्षा जल में वायुमंडलीय ऑक्सीजन विद्यमान होता है ।
उपर्युक्त कथनों के संबंध में, निम्नलिखित में से कौन-सा सही है ?
Read this question in English
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
उत्तर और व्याख्या · explanation in English
Answer: (a) कथन-II और कथन-III दोनों सही हैं तथा दोनों, कथन-I की व्याख्या करते हैं
Chemical weathering works through water, oxygen and carbon dioxide. Falling rain dissolves both gases from the air: the dissolved carbon dioxide forms a weak acid that attacks rocks (carbonation), and the dissolved oxygen oxidises minerals such as iron. So both II and III are true and each explains why rain weathers rock.
- ✓ Statement-I Rainwater drives chemical weathering processes such as solution, carbonation, hydration and oxidation.
- ✓ Statement-II Rain dissolves atmospheric carbon dioxide and becomes weakly acidic; this acid dissolves minerals, especially in limestone (carbonation). It explains Statement-I.
- ✓ Statement-III Rain also carries dissolved oxygen, which oxidises iron-bearing minerals and weakens the rock. It too explains Statement-I.
Remember · Chemical weathering needs water plus air — oxygen (oxidation) and carbon dioxide (carbonation). Rainwater brings both.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter)
Sources
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction 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.”
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “Water and air (oxygen and carbon dioxide) along with heat must be present to speed up all chemical reactions.”
Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·