Question

Chlorofluorocarbon releases _______ which is harmful to ozone
(a) fluorine
(b) chlorine
(c) nitrogen peroxide
(d) Sulphur dioxide

Answer 1

Hint: The catalyst which is used to convert ozone into molecular oxygen and is released from Chlorofluorocarbons due to the action of UV rays.

Complete step by step answer:
Chlorofluorocarbons (CFCs) when released into the stratosphere release chlorine atoms by the action of UV rays. These chlorine atoms act as a catalyst for the conversion of ozone into molecular oxygen.
Ozone gas is formed continuously in the stratosphere from molecular oxygen by the action of UV rays which is unstable. Generally, there will be a balance between the production and degradation of ozone in the stratosphere. This is distributed by chlorofluorocarbons(CFCs). When CFCs are released into the lower strata of the atmosphere called the troposphere, move upward and reach the upper strata of the atmosphere called the stratosphere. Due to the action of UV rays, chlorine atoms are released from CFCs. This acts as a catalyst for the conversion of ozone into molecular oxygen. As we know that catalyst is not utilized in the reaction, it only enhances the reaction time. Since chlorine is a catalyst, it is not consumed in the reaction and it continues to degrade ozone. The CFCs which are added to the stratosphere have permanent and continuing effects on the ozone levels.
The depletion of ozone in the antarctic region is particularly marked which resulted in the formation of a thin layer of ozone, called 'ozone hole'
Chlorofluorocarbons are widely used as coolants and refrigerants.
So, the correct answer is 'Chlorine'.

Note:
- UV radiation with shorter wave-length than UV-B is completely absorbed by the earth's atmosphere which indicates that the ozone layer is not completely damaged.
- Montreal Protocol was signed in 1987 for reducing the emission of CFCs and other ozone- depleting chemicals.