Examkin

Question

Difficulty: MediumAir Pollutants, Photochemical Smog, and Acid Rain

In atmospheric chemistry, air pollutants are classified based on whether they are released directly from source emissions or formed via atmospheric reactions. Which of the following is a secondary pollutant produced during the formation of photochemical smog?

  1. Peroxyacetyl nitrate (PAN\text{PAN})Answer
  2. B
    Carbon(II) oxide (CO\text{CO})
  3. C
    Sulfur(IV) oxide (SO2\text{SO}_2)
  4. D
    Methane (CH4\text{CH}_4)

Answer

Peroxyacetyl nitrate (PAN\text{PAN}) is a secondary air pollutant formed through photochemical reactions between unburnt hydrocarbons and nitrogen oxides in the presence of sunlight.
Peroxyacetyl nitrate (PAN\text{PAN}) is classified as a secondary pollutant because it is not emitted directly from any industrial or natural source; instead, it is synthesized in ambient air through complex photochemical reactions between nitrogen oxides and unburnt hydrocarbons driven by sunlight.

Step-by-Step Solution

1
Differentiate between primary and secondary air pollutants.
Primary pollutants are emitted directly from sources (e.g., CO\text{CO}, SO2\text{SO}_2, CH4\text{CH}_4), whereas secondary pollutants form in the atmosphere through chemical transformations of primary pollutants.
Classification depends on whether the chemical is directly emitted or formed chemically in ambient air.
2
Identify the constituents and origin of photochemical smog.
Photochemical smog forms when sunlight drives reactions between nitrogen oxides (NOx\text{NO}_x) and volatile organic compounds (hydrocarbons), forming ozone (O3\text{O}_3) and peroxyacetyl nitrate (PAN\text{PAN}).
PAN\text{PAN} is a toxic component of smog created exclusively by atmospheric chemical processes.

Key Concept

Secondary Air Pollutants and Photochemical Smog Formation
Estimated Time:1m 0s
Rate this question

Topics

Air Pollutants, Photochemical Smog, and Acid Rain

More questions from this topic