Question

Which of the following statements about photochemical smog is wrong?
(correct answer +1, wrong answer -0.25)

• A. It has high concentration of oxidising agents
• B. It has high concentration of reducing agents
• C. It can be controlled by controlling the release of $N{O}_2$, hydrocarbons, ozone
• D. PAN is the potent eye irritant found in the smog

Answer 1

The correct option is B It has high concentration of reducing agents

Photochemical smog is an oxidising smog having high concentration of oxidants. Photochemical smog is characterised by brown, hazy fumes. It is formed in the atmosphere which is highly loaded with automobile exhausts, trapped by inversion layer and at the same time exposed to intense sunlight. Hydrocarbons do not react readily with sunlight but, they are reactive towards other substances produced photochemically.
London smog contains reducing agents whereas photochemical smog contains oxidising agents.
Major contributors of photochemical smog are reactive hydrocarbons, ozone, oxygen, $NO$, $N{O}_2$.

Hence, photochemical smog can be controlled by controlling the release of $N{O}_2$, hydrocarbons, ozone.
The aldehyde may initiate the another route by interaction with $O{H}^{.}$ radical, leading to formation of peroxyacyl nitrate (PAN) which is the potent eye irritant found in the smog.