Question

Photochemical smog consists of excessive amount of $X$, in addition to aldehydes, ketones, peroxyacetyl nitrile $(PAN)$, and so forth. $X$ is :

• A. $CH_4$
• B. $CO$
• C. $CO_2$
• D. $O_3$

Answer 1

The Correct Option is D

Photochemical smog is a type of air pollution that results from the reaction of sunlight with pollutants such as hydrocarbons and nitrogen oxides in the atmosphere. This smog is most common in urban areas and is more prevalent during the summer months when the sunlight is intense. 

The major components of photochemical smog include:

• Aldehydes and ketones
• Peroxyacetyl nitrate (PAN)
• Ground-level ozone (\(\))

The presence of ground-level ozone is one of the key indicators of photochemical smog. Ozone at this level is different from the ozone in the stratosphere that protects us from ultraviolet rays. In the context of smog, ozone is a harmful pollutant that contributes to respiratory problems and other health issues.

Let's examine the options provided:

• \(CH_4\): Methane is a greenhouse gas but not directly a component of photochemical smog.
• \(CO\): Carbon monoxide is a pollutant but not a primary component of photochemical smog.
• \(CO_2\): Carbon dioxide is a greenhouse gas and is not directly involved in the formation of photochemical smog.
• \(O_3\): Ozone is a major component of photochemical smog, formed by the reaction of sunlight with hydrocarbons and nitrogen oxides.

Therefore, the substance represented by \(X\) in photochemical smog is indeed ozone (\(O_3\)).

Correct Answer: \(O_3\)