Given below are two statements: one is labelled as Assertion A and the other…
2023
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Despite the fact that Chloro Fluoro Carbons (CFCs) are evenly distributed over the globe, the Ozone depletion is significantly pronounced over the south pole.
Reason R: The presence of ice crystals over the south pole makes chlorine to oxygen bonding tougher.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer: C. A is correct but R is not correct — CONCEPTOzone depletion depends on catalytic reaction cycles: a chlorine radical is regenerated while converting ozone into ordinary oxygen, so a small amount…
- 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
Show answer & explanation
Correct answer: C
CONCEPT
Ozone depletion depends on catalytic reaction cycles: a chlorine radical is regenerated while converting ozone into ordinary oxygen, so a small amount of active chlorine can destroy many ozone molecules.
In very cold polar winters, polar stratospheric cloud particles provide surfaces for heterogeneous reactions that convert relatively inactive chlorine reservoir compounds into forms that release reactive chlorine when sunlight returns.
APPLICATION
Assertion A describes the observed Antarctic ozone hole: ozone loss is far more pronounced over the South Pole even though long-lived CFCs become broadly mixed through the atmosphere.
The polar concentration of ozone loss is explained by Antarctic winter temperatures, polar stratospheric clouds, isolation inside the polar vortex, and the return of spring sunlight, which together activate chlorine chemistry.
Reason R says ice crystals make chlorine–oxygen bonding tougher. That is not the relevant mechanism: cloud-particle surfaces promote reactions that convert reservoir species such as HCl and ClONO2 into photolabile chlorine, rather than strengthening a chlorine–oxygen bond.
CROSS-CHECK / CONTRAST
The response claiming both statements are true and causally linked treats stronger chlorine–oxygen bonding as the polar mechanism, which does not describe polar stratospheric-cloud chemistry.
The response claiming both statements are true but unrelated still requires the bond-strength statement to be scientifically correct.
The response claiming Assertion A is false conflicts with the well-established seasonal Antarctic ozone hole.
Therefore, Assertion A is correct, but Reason R is not correct.