Question

Photochemical smog always contains
(a) Aluminium ions
(b) Methane
(c) Ozone
(d) Phosphorous

Answer 1

Smog is a type of severe air pollution which is coined as a contraction of the words Smoke and Fog. It can be classical/industrial smog and photochemical smog. Photochemical smog has many chemicals and it always contains a gas that makes up a protective layer in the stratosphere.

Complete Step by Step Answer:
Smog is a severe type of air pollution which is also a kind of visible air pollution composed of nitrogen oxides, sulfur oxides, smoke, and ozone along with certain other particulates. Smog can be of various types but mainly divided into Man- made or Classical or Industrial and Photochemical smog.
Photochemical smog is a type of air pollution that is derived from vehicular emissions and the burning of agricultural wastes, the fumes from which react with the sunlight to form secondary pollutants. They combine with the primary emissions such as toxic gases, sulfur oxides, etc to form the photochemical smog. Photochemical smog also referred to as Summer smog is the chemical reaction of sunlight with nitrogen oxides and some organic compounds along with the formation of secondary pollutants such as Peroxylacyl nitrates (PAN), aldehydes, and Ozone. The photochemical smog always contains the Ozone gas or ${O}_{3}$ as a pollutant.
So, the correct answer is, “Ozone”.

Note:
- The presence of ozone is explained by a concept known as the photostationary state. The ozone is usually destroyed by its reaction with nitrogen monoxide to form nitrogen dioxide. But in photochemical smog, there are other chemicals to derive ${N}{O}_{2}$ from. Due to this reason, the levels of Ozone increases.
- This photochemical smog can sometimes be caused in case of a natural calamity such as volcanic eruptions. Some trees have also been shown to produce Volatile Organic Compounds or VOCs which can lead to smog formation.