Question

Photochemical smog consists of excessive amounts of X, in addition to aldehydes, ketones, peroxyacetyl nitrile (PAN), and so forth. X is:

(A) {{\text{ }}{O_3}} \\\ (B) {{\text{ }}C{H_4}} \\\ (C) {{\text{ }}C{O_2}} \\\ (D) {{\text{ }}CO} \end{array}$$

Answer 1

Photochemical smog is a type of smog that appears in morning and afternoon in dense populated areas.it is produced when ultraviolet light from the sun reacts with nitrogen oxides in the atmosphere. Photochemical smog consists of excessive amounts of ozone (${O_3}$).

Complete step by step solution: Photochemical smog is a type of smog, which is produced when in the atmosphere, ultraviolet light from the sun reacts with oxides of nitrogen. It is visible as a brown haze. It is most commonly seen during the morning and afternoon in densely populated and warm locations. The largest contribution in photochemical smog is of automobiles. Coal-fired power plants and other power plants also produce pollutants because of the production of photochemical smog. NO2, ozone and peroxy acetyl nitriles (PAN) are the main components of photochemical smog because they can react and oxidize many compounds in the atmosphere and within a person's lungs which are not oxidized normally. Photochemical smog has many adverse effects on humans, animals as well as on vegetation. Small traces of these chemicals can affect the respiratory tract of humans and animals. It can also damage crops and trees. When the smog causes chemicals combined with hydrocarbons, they can form molecules which cause eye irritation. In the air, radicals created by smog interfere with the nitrogen cycle by preventing the destruction of ground level ozone. Other effects include reduced visibility in humans.

Hence, the correct option is (A) ${O_3}$

Note: Ozone of photochemical smog interacts with reactive hydrocarbons (containing C=C bond) to form hydrocarbon free radicals. These radicals cause eye irritation and reduce visibility.