Name: Environmental Education - 1
Uploaded: 2019-07-19
Duration: 25 min 8 s
Description: In this video, we will discuss the concept and features of environmental education for the UGC net exam. Let's watch this video till the end.

Question

How is photochemical smog formed? What are its effects? How can it be controlled?

Accepted Answer

Photochemical smog is formed when the air contains ${NO}_{2}$ and hydrocarbons and the mixture is exposed to sunlight. As the reaction take place in the presence of sunlight to form the smog. In the presence of sunlight ${NO}_{2}$ undergoes photolysis to form $NO$ and atomic oxygen. Atomic oxygen then combines with the molecular oxygen in the presence of some molecule M (which acts as a source of transfer of energy) to form ozone, $O_{3}$ . The ozone thus formed reacts with $NO$ to regenerate ${NO}_{2}$ and $O_{2}$ . Thus ${NO}_{2}$ cycle completed. The reaction takes place as follows;

${NO}_{2} \overset{hv}{\to} NO + O O + O_{2} \to O_{3} O_{3} + NO \to {NO}_{2} + O_{2}$

Thus $NO$ and $O_{3}$ produced are used up and no extra ${NO}_{2}$ is added into the atmosphere.

The effects of photochemical smog are:

The pungent smelling, smog produced ozone is known to be toxic. It can cause coughing, wheezing bronchitis and irritation to mucous system.

It can be controlled by:

(1) Fitting efficient catalytic converters in the automobiles so that the emission of nitrogen oxides and hydrocarbons by these automobiles into the atmosphere can be prevented.

(2) By spraying certain compounds into the atmosphere which generate free radicals that readily combine with the free radicals that initiate the reactions forming toxic compounds of the photochemical smog.

How is photochemical smog formed? What are its effects? How can it be controlled?

Important Questions on Atmospheric Pollution

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