Air Pollution MCQ with answer and solution

Concept

Classification of secondary air pollutants

Formula

NONE

Step-by-step solution

1. Primary pollutants are emitted directly from identifiable sources into the atmosphere. 2. Secondary pollutants are formed in the atmosphere through chemical reactions involving primary pollutants. 3. Peroxy-acetyl-nitrate (PAN) forms via photochemical reactions between nitrogen oxides and volatile organic compounds, making it a secondary pollutant. Answer: D

Explanation

Primary air pollutants are emitted directly into the atmosphere from identifiable sources like industrial stacks or motor vehicles. Secondary air pollutants form through chemical reactions between primary pollutants and atmospheric components in the presence of sunlight. Peroxy-acetyl-nitrate is a secondary pollutant produced by photochemical reactions involving hydrocarbons and nitrogen oxides.

Why the other options are wrong

A) Sulphur dioxide is emitted directly from combustion sources and is a primary pollutant. B) Hydrocarbons are released directly into the atmosphere and represent primary pollutants. C) Carbon monoxide is directly emitted from incomplete combustion and is a primary pollutant.

Shortcut

Primary pollutants (SO2, CO, HC) are directly emitted; secondary pollutants (PAN, O3) are formed in the atmosphere.

Common mistake

Confusing secondary air pollutants formed photochemically in the atmosphere like PAN with directly emitted primary pollutants like SO2, CO, or hydrocarbons.