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 defferent enthalpy of bond dissociation
In the light of the above statements, choose the correct answer from the options given below :

Options

A. Both A and R are correct but R is NOT the correct expanation of A
B. Both A and R are correct but R is the correct explanation of A
C. A is correct but R is not correct
D. A is not correct but R is not correct

Answer

To solve the question, we need to analyze both the Assertion (A) and the Reason (R) statements provided.

### Step 1: Analyze the Assertion (A)
**Assertion A** states: "Isotopes of hydrogen have almost the same chemical properties, but difference in their rates of reaction."

- **Explanation**: Isotopes of hydrogen (such as protium, deuterium, and tritium) have the same number of protons and electrons, which means they exhibit similar chemical behavior. However, their differing atomic masses lead to variations in their kinetic energy and reaction rates, resulting in different rates of reaction.

### Step 2: Analyze the Reason (R)
**Reason R** states: "Isotopes of hydrogen have different enthalpy of bond dissociation."

- **Explanation**: The bond dissociation enthalpy refers to the energy required to break a bond in a molecule. Isotopes of hydrogen have different masses, which affects the vibrational energy levels of the bonds they form. This results in different bond dissociation enthalpies for the isotopes, contributing to the differences in their reaction rates.

### Step 3: Determine the correctness of Assertion and Reason
- Both the assertion and the reason are correct statements.
- However, while the reason provides a valid explanation for the difference in reaction rates, it does not directly explain why the chemical properties are similar.

### Conclusion
Based on the analysis:
- **Assertion A is correct**: Isotopes have similar chemical properties but different reaction rates.
- **Reason R is correct**: Isotopes have different enthalpy of bond dissociation.
- However, **Reason R is not the correct explanation for Assertion A**.

### Final Answer
The correct option is: **Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.**

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