Question

Which of the following pairs is secondary precursors of photochemical smog –

• A. $S{O}_{2}andN{O}_2$
• B. $S{O}_2$ and hydrocarbons
• C. $N{O}_2$ and hydrocarbons
• D. $O_3$ and PAN

Answer 1

The correct option is D $O_3$ and PAN

Photochemical smog does not contain $S{O}_2$. Hence we straight away discard options (a) and (b).

$N{O}_2$ and hydrocarbons are primary precursors while $O_3$, PAN, Formaldehyde, and Acrolein are secondary precursor of photochemical smog.