Given below are two statements: One is labelled as Assertion A and the other…
2022
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion (A): Chlorofluorocarbons (CFCs) are potent greenhouse gases.
Reason (R): CFCs have the ability to catalytically destroy ozone in stratosphere.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer: B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A) — CONCEPTThe greenhouse effect and stratospheric ozone depletion are different atmospheric processes. A greenhouse gas warms the climate by absorbing outgoing…
- A.
Both (A) and (R) are correct and (R) is the correct explanation of (A)
- B.
Both (A) and (R) are correct but (R) is NOT the correct explanation of (A)
- C.
(A) is correct but (R) is not correct
- D.
(A) is not correct but (R) is correct
Attempted by 1 students.
Show answer & explanation
Correct answer: B
CONCEPT
The greenhouse effect and stratospheric ozone depletion are different atmospheric processes.
A greenhouse gas warms the climate by absorbing outgoing infrared radiation, whereas ozone depletion occurs when reactive radicals catalytically convert ozone into oxygen and are regenerated in the cycle.
APPLICATION
CFC molecules absorb infrared radiation and have long atmospheric lifetimes, so Assertion (A) is true.
Ultraviolet light breaks CFC molecules in the stratosphere and releases chlorine radicals; these radicals participate in catalytic cycles that destroy ozone, so Reason (R) is also true.
However, the ozone-destruction mechanism does not cause the infrared absorption responsible for the greenhouse effect.
CONTRAST
The claim that Reason (R) explains Assertion (A) joins two distinct mechanisms.
The claim that Reason (R) is false overlooks chlorine-radical ozone-loss cycles.
The claim that Assertion (A) is false overlooks infrared absorption and radiative forcing by CFCs.
RESULT
Therefore, both Assertion (A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).