Question

Which one of the following is not a common component of Photochemical Smog?

• A. Ozone
• B. Acrolein
• C. Peroxyacetyl nitrate
• D. Chlorofluorocarbon

Answer 1

The correct option is D

Chlorofluorocarbon

The explanation for the correct answer:

Photochemical smog:

1. This photochemical smog is basically a mixture of pollutants and these are formed when the nitrogen oxides, as well as the Volatile Organic Compounds (VOCs), will react in the presence of sunlight during the daytime.
2. This all will create a brown haze above the cities.
3. Here, in this, the major pollutants are nitrogen oxides and VOC which will combine to just change in the presence of sunlight and follow a series of chemical reactions.
4. Then comes the secondary pollutants which will get formed at the ground level and here the ozone will get produced naturally in the upper atmosphere.
5. Basically, the composition includes a mixture of ozone, aldehydes, nitric acid, peroxyacetyl nitrates (PANs), and also many other secondary pollutants
6. The series of chemical reactions for the formation of photochemical smog is as follows:

$$\begin{gathered} \underset{\mathrm{Nitrogen}\mathrm{dioxide}}{{\mathrm{NO}}_2\left(\mathrm{g}\right)}\stackrel{\mathrm{hv}}{\to }\underset{\mathrm{Nitrogen}\mathrm{oxide}}{\mathrm{NO}\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)} \\ \underset{\mathrm{Oxygen}\mathrm{atom}}{\mathrm{O}\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}\mathrm{molecule}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\rightleftharpoons \underset{\mathrm{Ozone}}{{\mathrm{O}}_3\left(\mathrm{g}\right)} \\ \underset{\mathrm{Ozone}}{{\mathrm{O}}_3\left(\mathrm{g}\right)}+\underset{\mathrm{Nitrogen}\mathrm{oxide}}{\mathrm{NO}\left(\mathrm{g}\right)}\to \underset{\mathrm{Nitrogen}\mathrm{dioxide}}{{\mathrm{NO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)} \\ \underset{\mathrm{Methane}}{3{\mathrm{CH}}_4\left(\mathrm{g}\right)}+\underset{\mathrm{Ozone}}{2{\mathrm{O}}_3\left(\mathrm{g}\right)}\to \underset{\mathrm{Formaldehyde}}{3{\mathrm{CH}}_2=\mathrm{O}\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)} \end{gathered}$$

The explanation for the incorrect answers:

The major undesirable components of photochemical smog are nitrogen dioxide (${\mathrm{NO}}_2$), ozone (${\mathrm{O}}_3$), PAN (peroxyacetylnitrate), and chemical compounds that contain the –CHO group (aldehydes)(acrolein). PAN and aldehydes can cause eye irritation and plant damage if their concentrations are sufficiently high.

Option (A): Ozone- Photochemical smog contains ozone as its main component.

Option (B): Acrolein- Photochemical smog contains acrolein as its main component.

Option (C): Peroxyacetyl nitrate- Photochemical smog contains peroxyacetyl nitrate as its main component.

Therefore, the correct option is (D): Chlorofluorocarbon