Assertion : Potassium is not obtained by the electrolysis of fused `KCl`.
Reason : Potassium vapourises at the melting point of `KCl`.

Options

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

Answer

To solve the question regarding the assertion and reason about potassium and the electrolysis of fused KCl, we can break it down into a step-by-step explanation.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Potassium is not obtained by the electrolysis of fused KCl." This means that during the process of electrolysis of potassium chloride in its molten state, potassium metal cannot be produced.

**Hint**: Consider the properties of potassium and how they relate to the electrolysis process.

2. **Understanding the Reason**:
- The reason given is "Potassium vaporizes at the melting point of KCl." This implies that when KCl is melted (at its melting point of 1063 K), potassium, which has a lower boiling point (1039 K), will vaporize rather than remain in liquid form.

**Hint**: Compare the boiling point of potassium with the melting point of KCl to understand the behavior of potassium during electrolysis.

3. **Analyzing the Melting and Boiling Points**:
- KCl has a melting point of 1063 K and a boiling point of 1039 K. Since the boiling point of potassium is lower than the melting point of KCl, potassium will vaporize when KCl is melted.

**Hint**: Remember that if a substance vaporizes, it cannot be collected as a liquid or solid during electrolysis.

4. **Conclusion**:
- Since potassium vaporizes at the melting point of KCl, it cannot be obtained as a product during the electrolysis of fused KCl. Therefore, both the assertion and reason are true, and the reason correctly explains why the assertion is true.

**Hint**: Think about how the physical states of elements during electrolysis affect the outcomes of the process.

### Final Answer:
Both the assertion and the reason are true, and the reason is the correct explanation of the assertion. Thus, the correct option is that both statements are true, and the reason is the correct explanation for the assertion.