Acid rain is caused by the presence of which gases in the atmosphere?
A. H₂ and He
B. SO₂ and NOₓ
C. O₂ and N₂
D. CO₂ and CO
Answer: Option B
Solution (By JKExamLibrary)
Acid rain results from SO₂ and NOₓ (from burning fossil fuels) reacting with water vapor to form sulfuric and nitric acids. Normal rain is slightly acidic (pH ~5.6) due to CO₂ forming carbonic acid, but acid rain has pH < 5.6. Effects include corrosion of monuments (Taj Mahal), damage to aquatic life, and soil acidification. CO₂ causes global warming, not primarily acid rain.
Explanation:
Sublimation is the direct transition from solid to gas phase. Examples: naphthalene, camphor, iodine, solid CO₂ (dry ice). Evaporation is liquid to gas; condensation is gas to liquid; distillation separates liquid mixtures based on boiling points.
Explanation:
Atomic radius increases down a group due to addition of shells. Lithium (Z=3, 2 shells) is the first element in Group 1 and has the smallest radius. Cesium has the largest. The effective nuclear charge also plays a role, but shell number dominates. Trend: Li < Na < K < Rb < Cs.
Explanation:
Ozonation is a powerful disinfection method that kills bacteria and viruses faster than chlorine. Unlike chlorine, ozone decomposes back into oxygen and does not leave a residual taste or form harmful chlorinated organic byproducts (like trihalomethanes), making it safer for drinking water.
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