Correct option is D
Introduction
Acid rain forms when sulphur and nitrogen oxides dissolve in atmospheric moisture to produce sulphuric and nitric acids. Its severity depends on pollutant solubility, water content, and the buffering capacity of underlying bedrock.
Information Booster
In reality, fog and mists at high altitudes are typically more acidic, not less, than ordinary precipitation.
This is because fog and mist droplets are far smaller and have much less water volume per unit of dissolved acid, so the acidic pollutants become highly concentrated rather than diluted.
Fog droplets also have a very high surface-area-to-volume ratio, allowing them to scavenge gaseous and particulate pollutants efficiently, and they linger in contact with polluted air for longer periods.
Measured fog-water pH values are often substantially lower (more acidic) than co-located rainfall.
The statement's reasoning — that "more water availability for dilution" makes fog less acidic is the opposite of the truth, since fog actually offers less water for dilution, making (d) the incorrect statement and thus the answer.
Additional knowledge
· Nitric oxide is not especially soluble in water and thus NO itself does not make rainwater particularly acidic — Correct. NO must first be oxidised in the atmosphere to NO₂ and then to nitric acid (HNO₃) before it meaningfully acidifies rainwater; NO itself has low solubility and limited direct effect.
· Neutralization of acid rain by limestone produces carbon dioxide — Correct. The reaction of acid with calcium carbonate (CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂) releases carbon dioxide, which is the standard neutralisation chemistry of carbonate bedrock.
· Areas with granite or quartz bedrock are more affected than carbonate areas — Correct. Granite and quartz have little acid-neutralising (buffering) capacity, so acid rain impacts persist, whereas carbonate (limestone) bedrock buffers acidity effectively, protecting soils and waters.
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