Some reactions of NO_2 relevant to photochemical smog formation are NO_2 →[sunlight] X + Y X →[A] B Identify A, B, X and Y

X = [O], Y = NO, A = O_2, B = O_3

X = 1/2O_2, Y = NO_2, A = O_3, B = O_2

X = N_2O, Y = [O], A = O_3, B = NO

X = NO, Y = [O], A = O_2, B = N_2O_3

Some reactions of NO_2 relevant to photochemical smog… — JEE Main 2023 Chemistry PYQ

JEE Main 2023 · 25 Jan · Shift 1

Some reactions of

\text{NO}_2

relevant to photochemical smog formation are

\text{NO}_2 \xrightarrow{\text{sunlight}} X + Y

X \xrightarrow{A} B

Identify A, B, X and Y

A.
$X = [O]$ , $Y = NO$ , $A = O_2$ , $B = O_3$
B.
$X = \frac{1}{2}O_2$ , $Y = NO_2$ , $A = O_3$ , $B = O_2$
C.
$X = N_2O$ , $Y = [O]$ , $A = O_3$ , $B = NO$
D.
$X = NO$ , $Y = [O]$ , $A = O_2$ , $B = N_2O_3$

Show answer and solution

Correct option: A

Solution

In photochemical smog chemistry, NO₂ absorbs UV sunlight and undergoes photodissociation: NO₂ → NO + [O], so X = [O] (nascent/atomic oxygen) and Y = NO. The highly reactive atomic oxygen then reacts with molecular oxygen in the air: [O] + O₂ → O₃, so A = O₂ and B = O₃. This ozone formation is the key step in photochemical smog, as O₃ is a powerful oxidant responsible for the harmful effects observed.

[JEE Main 2023 · 25 Jan · Shift 1]

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