Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Heavy water is used for the study of reaction mechanism.
Reason (R): The rate of reaction for the cleavage of bond is slower than that of O-D bond.
Choose the most appropriate answer from the options given below:
Assertion (A): Heavy water is used for the study of reaction mechanism.
Reason (R): The rate of reaction for the cleavage of bond is slower than that of O-D bond.
Choose the most appropriate answer from the options given below:
- (A)(A) is true but (R) is false.✓ Correct
- (B)(A) is false but (R) is true.
- (C)Both (A) and (R) are true but (R) is the true explanation of (A).
- (D)Both (A) and (R) are true and (R) is not the true explanation of (A).
Answer: (A)
Solution
Replacing hydrogen by the heavier deuterium lowers the zero-point energy of the bond, so an bond needs more energy to break than an bond and is cleaved more slowly. Comparing rates in and in therefore reveals whether such a bond is broken in the rate-determining step, and this kinetic isotope effect is why heavy water is a standard tool for probing reaction mechanisms, so the assertion is true. The reason reverses the two cleavage rates and is false. The assertion is true but the reason is false.
JEE Main · 2021 · 26 Aug 2021 · Shift 2 · Single correct option