Question

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

• 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

Answer 1

The Correct Option is A

Isotopes of hydrogen, such as protium, deuterium, and tritium, have the same electronic configuration, so they exhibit almost identical chemical properties. However, due to their differences in mass, the rates of reactions differ significantly, primarily because of differences in the enthalpy of bond dissociation. 

The enthalpy of bond dissociation is higher for heavier isotopes (such as deuterium and tritium) compared to protium, leading to slower reaction rates for the heavier isotopes. Hence, both the assertion (A) and reason (R) are correct, and the reason (R) correctly explains the assertion (A).