Question

The main source of photochemical smog in most areas is?

1) automobiles
2) electric power plants
3) chemical factories
4) solid waste burning

Answer 1

Automobiles are the main source of photochemical smog in most areas, due to emissions of nitrogen oxides and volatile organic compounds reacting with sunlight.

Step-by-step explanation:

The main source of photochemical smog in most areas is automobiles. This type of air pollution is mainly due to the reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) with sunlight, which commonly occurs over urban areas. Here is a brief step-by-step explanation of photochemical smog formation initiated by vehicle emissions:

1. Nitrogen oxidation: In the mornings, as people start driving, nitrogen from car engines is oxidized (N₂ + O₂ → 2NO).
2. Nitrogen dioxide formation: NO then reacts with more oxygen to form nitrogen dioxide (2NO + O₂ → 2NO₂).
3. Light energy absorption: NO₂ absorbs light energy and dissociates into NO and an oxygen atom (NO₂ → NO + O).

Subsequent reactions of these components with other atmospheric compounds lead to the formation of smog, with ground-level ozone being a major component.

Factors such as gas powered vehicles, which are prevalent in urban environments, make them a significant contributor to this pollution.

Vehicles equipped with catalytic converters help to reduce emissions that lead to photochemical smog, but automobiles nonetheless remain a primary source.