Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Isotopes of hydrogen have almost same chemical properties, but difference in their rates of reaction.
Reason R : Isotopes of hydrogen have different enthalpy of bond dissociation.
In the light of the above statements, choose the most appropriate answer from the options given below:
Assertion A : Isotopes of hydrogen have almost same chemical properties, but difference in their rates of reaction.
Reason R : Isotopes of hydrogen have different enthalpy of bond dissociation.
In the light of the above statements, choose the most appropriate answer from the options given below:
- (A)Both A and R are correct but R is NOT the correct explanation of A
- (B)Both A and R are correct and R is the correct explanation of A✓ Correct
- (C)A is not correct but R is correct
- (D)A is correct but R is not correct
Answer: (B)
Solution
Both statements are correct and R correctly explains A.
Isotopes of hydrogen (, or D, and or T) have the same electronic configuration (1s¹), so they have almost identical chemical properties. However, their reaction rates differ significantly.
The reason for different rates is that the bond dissociation enthalpies are different: H-H (436 kJ/mol), D-D (443 kJ/mol), T-T (446 kJ/mol). The heavier isotopes form stronger bonds due to lower zero-point energy, leading to slower reaction rates (kinetic isotope effect). Thus R correctly explains A.
Isotopes of hydrogen (, or D, and or T) have the same electronic configuration (1s¹), so they have almost identical chemical properties. However, their reaction rates differ significantly.
The reason for different rates is that the bond dissociation enthalpies are different: H-H (436 kJ/mol), D-D (443 kJ/mol), T-T (446 kJ/mol). The heavier isotopes form stronger bonds due to lower zero-point energy, leading to slower reaction rates (kinetic isotope effect). Thus R correctly explains A.
JEE Main · 2023 · 13 Apr 2023 · Shift 2 · Single correct option