Assertion. When 1.0 mol of NaCl is doped with `10^(-3)` mol `SrCl_2`, the number of cationic sites remaining vacant is `10^(-3)`
Reason. Each `SrCl_2` unit produces two cation vacancies.

Options

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

Explanation

To solve the question, we will analyze the assertion and reason provided regarding the cationic vacancies created when NaCl is doped with SrCl₂.

### Step 1: Understand the Composition of SrCl₂
- SrCl₂ consists of one strontium ion (Sr²⁺) and two chloride ions (Cl⁻). When SrCl₂ is introduced into the NaCl lattice, the strontium ion replaces a sodium ion (Na⁺) in the lattice.

**Hint:** Remember that each SrCl₂ unit contains one Sr²⁺ and two Cl⁻ ions.

### Step 2: Analyze the Cationic Vacancy Creation
- When Sr²⁺ replaces Na⁺, it creates a cationic vacancy because Sr²⁺ has a +2 charge, while Na⁺ has a +1 charge. This means that for every Sr²⁺ ion introduced, one Na⁺ ion is replaced, but there is an additional positive charge that creates a vacancy.

**Hint:** Focus on the charge difference between Na⁺ and Sr²⁺ to understand how vacancies are formed.

### Step 3: Calculate the Number of Vacancies
- According to the reason provided, each SrCl₂ unit produces two cation vacancies. However, since we are replacing one Na⁺ with one Sr²⁺, we only create one cationic vacancy per SrCl₂ unit.

- If we have \(10^{-3}\) moles of SrCl₂, we would expect to create \(10^{-3}\) cationic vacancies, not two per unit.

**Hint:** Keep track of how many moles of SrCl₂ are present and how many vacancies are created per unit.

### Step 4: Evaluate the Assertion and Reason
- The assertion states that the number of cationic sites remaining vacant is \(10^{-3}\), which is correct.
- The reason states that each SrCl₂ unit produces two cation vacancies, which is incorrect. Each unit only produces one cation vacancy.

**Hint:** Compare the statements in the assertion and reason to determine their correctness.

### Conclusion
- The assertion is true, but the reason is false. Therefore, the correct evaluation is that the assertion is correct while the reason is incorrect.

### Final Answer
- The assertion is true, and the reason is false.