Environmental Chemistry - Result Question 13
####13. The molecule that has minimum/no role in the formation of photochemical smog, is
(a) $N _2$
(b) $CH _2=O$
(c) $NO$
(d) $O _3$
(2019 Main, 12 Jan I)
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Answer:
Correct Answer: 13. (d)
Solution:
- $N _2$ molecule has minimum role in the formation of photochemical smog. While $CH _2=O, O _3$ and $NO$ has major role. When fossil fuels are burnt, a variety of pollutants are emitted. Two of them are hydrocarbons (unburnt) and NO. When these pollutants build upto high levels, a chain reaction occurs from their interaction with sunlight. The reactions involved in the formation of photochemical smog are as follows:
$$ \begin{aligned} NO _2(g) \stackrel{h v}{ } & NO(g)+O(g) \ O(g)+O _2(g) & \rightleftharpoons O _3(g) \ NO(g)+O _3(g) & \longrightarrow NO _2(g)+O _2(g) \end{aligned} $$
$O _3$ reats with unburnt hydrocarbons to produce chemicals such as formaldehyde, acrolein and PAN.
$$ 3 CH _4+2 O _3 \longrightarrow CH _2=O+3 H _2 O $$
