Assertion : The product of magnetic susceptibility and absolute temperature for a paramagnetic substance is constant.
Reason: Susceptibility is positive but very small for paramagnetic substance.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true and reason is not the correct explanation of assertion.
C. If assertion is ture but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the given question, we will analyze both the assertion and the reason step by step.

### Step 1: Understanding the Assertion
The assertion states that "the product of magnetic susceptibility and absolute temperature for a paramagnetic substance is constant."

- For paramagnetic materials, the magnetic susceptibility (χ) is known to vary inversely with temperature (T). This relationship can be expressed mathematically as:

\[ \chi \propto \frac{1}{T} \]

### Step 2: Formulating the Relationship
From the relationship established in Step 1, we can express this as:

\[ \chi \cdot T = C \]

where \(C\) is a constant. This means that the product of magnetic susceptibility and absolute temperature remains constant for a paramagnetic substance.

### Step 3: Understanding the Reason
The reason states that "susceptibility is positive but very small for paramagnetic substances."

- This is indeed true. For paramagnetic materials, the magnetic susceptibility is positive, indicating that they are attracted to magnetic fields, but it is typically a small value.

### Step 4: Evaluating the Reason as an Explanation
While both the assertion and the reason are correct, we need to determine if the reason provides a correct explanation for the assertion.

- The assertion is about the relationship between magnetic susceptibility and temperature being constant, while the reason merely states that susceptibility is small and positive. The reason does not explain why the product of susceptibility and temperature is constant.

### Conclusion
Thus, we conclude that:
- The assertion is correct.
- The reason is correct but does not explain the assertion.

Therefore, the correct answer is that the assertion is true, the reason is true, but the reason is not a correct explanation of the assertion.

### Final Answer
The correct option is B: Assertion is true, Reason is true, but Reason is not the correct explanation of Assertion.

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