Environmental Chemistry - Result Question 23
####1. The primary pollutant that leads to photochemical smog is (2019 Main, 12 April II)
(a) acrolein
(b) nitrogen oxides
(c) ozone
(d) sulphur dioxide
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Answer:
Correct Answer: 1. (b)
Solution:
- The primary pollutant that leads to photochemical smog is nitrogen oxides. Burning of fossil fuels such as petrol and diesel in automobiles, reaction between nitrogen and oxygen and other such reactions result in a variety of pollutants, two main of which are hydrocarbons (unburnt fuel) and nitric oxide (NO).
$$ N _2(g)+O _2(g) \xrightarrow[\text { diesel engines }]{\text { In petrol and }} 2 NO(g) $$
When the concentration of these pollutants is sufficiently high, a chain reaction initiate because of the interaction of sunlight with oxides of nitrogen.
$$ \begin{aligned} & 2 NO(g)+O _2(g) \stackrel{\text { Sunlight }}{\longrightarrow} 2 NO _2(g) \ & NO _2(g) \stackrel{h v}{\longrightarrow} NO(g)+\underset{\begin{array}{c} \text { Nascent } \ \text { oxygen } \end{array}}{[O]} \ & O _3(g)+NO(g) \longrightarrow NO _2(g)+O _2(g) \end{aligned} $$
