Question

Photochemical smog consists of

• A. $O_3,S{O}_x$ and hydrocarbons
• B. $O_3,PAN\text{and}N{O}_x$
• C. $S{O}_2,C{O}_2$ and hydrocarbons
• D. $S{O}_2$, PAN and smoke

Answer 1

The correct option is B $O_3,PAN\text{and}N{O}_x$

Photochemical smog

Photochemical smog consists of nitrogen oxides, volatile organic compounds (VOCs), ozone, PAN (peroxyacetyl nitrate) etc.

Photochemical smog is formed when the oxides of nitrogen and volatile organic compounds react in the presence of sunlight to produce the secondary pollutants which combine with the existing pollutants to form smog.

Nitrogen oxides

Nitrogen oxides are released from the engines of automobiles like cars and trucks.

Ozone

Ozone is formed from the oxygen gas in reaction with UV light.

The $N{O}_2$ molecules released from automobiles absorb energy from sunlight and split into nitric oxide and free oxygen atoms. The free oxygen reacts and combines with the $O_2$ in the presence of the UV component of sunlight to produce ozone.

Peroxyacytyl nitrate

Peroxyacytyl nitrate (PAN) is formed by the reaction of ozone with unburnt hydrocarbons present in the polluted air.

Final answer

(B) $O_3,PANandN{O}_x$