2003 General Studies, all questions

UPSC Prelims 2003 · General Studies

Question 118: Environment and Ecology

Which one of following is produced during the formation of photochemical smog?

aHydrocarbons
bNitrogen Oxides
cOzone
dMethane

AnswerThe answer is (c).

Photochemical smog forms when sunlight acts on nitrogen oxides and hydrocarbons from vehicle exhaust. The products include ozone, peroxyacetyl nitrate (PAN) and aldehydes. Nitrogen oxides and hydrocarbons are the raw materials, not the products, which is why ozone is the answer here. Methane is a stable greenhouse gas and not a smog product.

Why each option is right or wrong
  • (a) Hydrocarbons are reactants, not products.
  • (b) Nitrogen oxides are the primary pollutants that start the reaction.
  • (c) Correct: ozone is formed.
  • (d) Methane is a stable greenhouse gas, not a smog product.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.