Question

Primary constituents of photochemical smog are

• A. $S{O}_2$ and CO
• B. $C{O}_2$ and $N{O}_2$
• C. $N{O}_2$ and unsaturated hydrocarbons
• D. Hydrocarbons and CFC's

Answer 1

The correct option is C $N{O}_2$ and unsaturated hydrocarbons

The photochemical reaction is caused by absorption of energy in the form of light. The word smog is formed of smoke and fog. Photochemical smog is the major contributor to air pollution and is composed of primary and secondary pollutants. Primary being the nitrogen oxides and volatile organic compounds. Unsaturated hydrocarbons are those that have double or triple covalent bonds between adjacent carbon atoms. e.g., Ethylene (C${}_2$H${}_4$). Gasoline and natural gas are major sources of unsaturated hydrocarbon. Butadiene, benzene are some hydrocarbons that are lethal to human health and have the potential to cause cancer.

Hence, the correct answer is 'NO${}_2$ and unsaturated hydrocarbons'.