Question

Photochemical smog formed in congested metropolitan cities mainly consists of

• A. ozone, peroxyacetyl nitrate and $N{O}_X$
• B. smoke, peroxyacetyl nitrate and SO
• C. hydrocarbons, ozone and $S{O}_X$
• D. hydrocarbons, $S{O}_2$ and $C{O}_2$

Answer 1

The correct option is A ozone, peroxyacetyl nitrate and $N{O}_X$

Photochemical smog
Photochemical smog consists of nitrogen oxides, volatile organic compounds (VOCs), ozone, and 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 the existing pollutants to form smog.

Nitrogen oxides are released from engines of 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 get hydrolysed into nitric oxide and free oxygen atoms. The free oxygen reacts and combines with the $O_2$ in the presence of air to produce ozone.

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

Final answer (A) ozone, peroxyacetyl nitrate and $N{O}_X$