Question

Which of the following groups of gases cause photochemical smog?
A.${O_3}$ , PAN and CO
B.$CH,NO$ and PAN
C.${O_{2,}}$ PAN and $N{O_2}$
D.${O_{2,}}$ PAN and $N{O_3}$
E.${O_{3,}}$ PAN and $N{O_2}$

Answer 1

Smog is a heavy fog and darker smoke caused by the action of ultraviolet radiation on the oxides of Sulphur. There are different types of smog like sulphurous smog, and photochemical smog. Photochemical smog is caused by ozone, peroxyacetyl nitrate and nitrogen dioxide.

Complete answer:
Atmosphere consists of different pollutants like oxides of Sulphur, and oxides of nitrogen. Ozone is a layer present on the earth which protects the earth from the dangerous ultraviolet radiation. Ozone consists of three oxygen atoms. Nitrogen dioxide is a pollutant that can be released from automobiles or industries.
Smog can be caused by the action of Ultraviolet radiation on the industries effluents like oxides of nitrogen and certain hydrocarbons. There are two types of smog like sulphurous smog, and photochemical smog.
Photochemical smog can occur from the ozone, peroxyacetyl nitrate and nitrogen dioxide. Thus, the main components of photochemical smog are nitrogen dioxide $\left( {N{O_2}} \right)$ , peroxyacetyl nitrate which is a secondary pollutant, and ozone.
${O_{3,}}$ PAN and $N{O_2}$ are the group of gases that cause photochemical smog.
Hence, option (E) is the correct answer.

Note:
Peroxyacetyl nitrate is a secondary pollutant which can be termed as PAN in the atmosphere and oxides of nitrogen lead to the photochemical smog. Oxides of Sulphur lead to the sulphurous smog. So, the difference between these two smog’s should be observed.