Assertion (A) is false: Electron affinity generally decreases as you move down a group due to increasing atomic radii and weaker nuclear attraction for the incoming electron. Additional electron shells increase the shielding effect, further reducing effective nuclear pull. Reason (R) is true: As you go down a group, additional electron shells are added, making the atomic radius increase. This is because the outermost electrons are farther from the nucleus, and the shielding effect from inner electrons increases. Directions: The following Items consist of two statements. One labeled as the ‘Assertion (A)’ and the other as 'Reason (R)'. You have to answer these items using the code given below: 325. Assertion (A): Coal-based thermal power stations contribute to acid-rain. Reason (R): Oxides of carbon are emitted when coal burns.

Question

YESPYQ · Accepted Answer

Correct answer: Both A and R are individually true but R is not the correct explanation of A. Assertion (A) is true: Coal-based thermal power stations contribute to acid rain because they release large amounts of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) into the atmosphere during coal combustion. These gases react with water vapor, oxygen, and other chemicals in the atmosphere to form sulfuric acid (H₂SO₄) and nitric acid (HNO₃), which then fall as acid rain. Reason (R) is true: When coal burns, it produces carbon dioxide (CO₂) and, to a lesser extent, carbon monoxide (CO), both of which are oxides of carbon. However, while oxides of carbon contribute to global warming, they do not directly contribute to acid rain. Oxides of carbon (CO₂ and CO) are emitted when coal burns, but they are not primary reasons for acid rain. Acid rain is primarily caused by sulfur dioxide (SO₂) and nitrogen oxides (NOₓ). Hence Reason (R) does not correctly explain the Assertion (A). UPSC GS Paper-I PYQs 604 326

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