Consider the following statements about Chlorofluorocarbons (CFCs) :
- 1. CFCs remain inert in the troposphere but slowly diffuse into the stratosphere.
- 2. CFCs in the upper atmosphere are subjected to UV radiations, generating free radical chlorine that immediately reacts with O₃ to form a radical called chlorine monoxide (ClO).
- 3. Each ClO can initiate a series of chemical reactions, leading to the destruction of the ozone layer.
How many of the statements given above is/are correct ?
1
2
3
None
Answer is Wrong!
Answer is Right!
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UPSC Geoscientist – 2024
– Statement 2 is correct: Once in the upper atmosphere (stratosphere), CFC molecules are exposed to high-energy ultraviolet (UV) radiation from the sun, which breaks the carbon-chlorine bond, releasing highly reactive free radical chlorine atoms (Cl•). A chlorine radical then reacts with an ozone molecule (O₃) to form chlorine monoxide (ClO•) and oxygen (O₂).
– Statement 3 is correct: The chlorine monoxide radical (ClO•) is also highly reactive. It can react with a free oxygen atom (O) (which is naturally present in the stratosphere from the breakdown of O₃) to form another chlorine radical (Cl•) and oxygen (O₂). The regenerated chlorine radical can then attack another ozone molecule, continuing the cycle. This chain reaction allows a single chlorine atom to destroy many thousands of ozone molecules before it is eventually removed from the stratosphere by other processes. This catalytic cycle leads to significant depletion of the ozone layer.