Question

Which of the following are the constituents of photochemical smog?
A. Aldehydes
B. Peroxyacyl nitrates
C. Volatile hydrocarbons
D. All of the above

Answer 1

Hint: Try to recall that photochemical smog is a chemical reaction between oxides of nitrogen and Volatile organic compounds (VOC’s) in the presence of sunlight. Now, by using this you can easily find the correct option from the given options.
Complete step by step solution:
1) It is known that previously smog was a combination of just smoke and fog.
2) But, today smog is a chemical reaction between oxides of nitrogen and volatile organic compounds in the presence of sunlight and this type of smog is known as photochemical smog.
3) Photochemical smog is brownish-yellow haze, primarily over urban areas. It is formed as a result of photochemical reactions taking place between oxides of nitrogen and volatile hydrocarbons forming ozone, peroxyacyl nitrates (PAN) and aldehydes (RCHO).
4) During the above photochemical reaction, ozone is formed very close to earth. This is bad ozone. It is harmful to breathe.
5) It does not allow impurities, like toxic fumes from burning petrol, to escape or dissipate into the atmosphere. Los Angeles is famous for this type of smog.
6) One of the most harmful toxic effects of photochemical smog is oxidative stress.

Therefore, from above we can easily conclude that option D is the correct option to the given question.

Note:
- It should be noted that to control photochemical smog, the catalytic converters are used in the automobile exhaust which in the first stage convert the oxides of nitrogen to free nitrogen gas or to a small amount of ammonia.
- Also, you should remember that photochemical smog tends to occur more often in summer because that is when we have the most sunlight.