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JEE Main levelSingle correct optionDifficulty 2 of 3ev079

In the troposphere, the oxygen atoms that lead to ozone in photochemical smog come mainly from

Aphotolysis of $NO X_{2}$ by sunlight
Bthermal decomposition of water vapour
Creaction of $CO$ with $H X_{2}$
Dphotolysis of $N X_{2}$

Answer: A

Sunlight splits nitrogen dioxide:

NO X_{2} NO + O

. The oxygen atom then combines with

O X_{2}

to give

O X_{3}

. Ordinary visible light cannot split

O X_{2}

in the troposphere.

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