Assertion (A) Separation of Zr and Hf is difficult.
Reason (R ) Because Zr and Hf lie in the same group of the Periodic Table.

Options

A. Both assertion and reason are true, and reason is the correct explanation of the assertion.
B. Both assertion and reason are true but reason is not the correct explanation of assertion.
C. Assertion is not true but reason is true.
D. Both assertion and reason are false.

Explanation

To solve the question regarding the assertion and reason about the separation of zirconium (Zr) and hafnium (Hf), we can break it down into a step-by-step analysis.

### Step 1: Understand the Assertion
The assertion states that "the separation of Zr and Hf is difficult." We need to analyze why this is the case.

### Step 2: Understand the Reason
The reason provided is that "Zr and Hf lie in the same group of the Periodic Table." This implies that they have similar properties due to their placement in the same group.

### Step 3: Analyze the Properties of Zr and Hf
Both zirconium and hafnium belong to Group 4 of the periodic table. Elements in the same group typically exhibit similar chemical and physical properties. This similarity can complicate the separation process.

### Step 4: Consider the Role of Lanthanoid Contraction
The difficulty in separating Zr and Hf is significantly influenced by the phenomenon known as lanthanoid contraction. The presence of lanthanides (the 14 f-block elements) before hafnium in the periodic table leads to a reduction in the size of the hafnium atom. This contraction results in hafnium having an atomic radius that is very similar to that of zirconium.

### Step 5: Conclusion on Assertion and Reason
- **Assertion (A)**: The separation of Zr and Hf is indeed difficult. This is true.
- **Reason (R)**: While it is true that Zr and Hf lie in the same group, the reason for their difficult separation is primarily due to lanthanoid contraction rather than just their group placement.

### Final Evaluation
Both the assertion and the reason are true, but the reason does not adequately explain the assertion. Therefore, the correct conclusion is that while both statements are correct, the reason is not the correct explanation for the assertion.

### Answer:
Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

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