Statement-1 : The ratio of `Zn^2+` and `F^(-)` per unit cell of ZnS and `CaF_2` is 1 :2
Statement-2 : In ZnS,`Zn^2+` ions occupy alternate tetrahedral voids and in `CaF_2, F^(-)` ions occupy all the tetrahedral voids of FCC unit cell.

Options

A. Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1
B. Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1
C. Statement-1 is True, Statement-2 is False.
D. Statement-1 is False, Statement-2 is True.

Explanation

To solve the problem, we need to analyze the two statements provided and verify their correctness, as well as the relationship between them.

### Step 1: Analyze Statement 1
**Statement 1**: The ratio of `Zn^2+` and `F^(-)` per unit cell of ZnS and `CaF_2` is 1:2.

- **ZnS Structure**: In ZnS, the `Zn^2+` ions occupy alternate tetrahedral voids. The `S^2-` ions form a face-centered cubic (FCC) lattice. In this structure, there are 4 `Zn^2+` ions per unit cell because there are 8 tetrahedral voids, and `Zn^2+` occupies half of them (4).

- **CaF2 Structure**: In CaF2, the `Ca^2+` ions form an FCC lattice, and the `F^(-)` ions occupy all the tetrahedral voids. In this structure, there are 8 tetrahedral voids, and since all are occupied by `F^(-)` ions, there are 8 `F^(-)` ions per unit cell.

Thus, the ratio of `Zn^2+` ions to `F^(-)` ions in their respective unit cells is:
- For ZnS: 4 `Zn^2+`
- For CaF2: 8 `F^(-)`

The ratio is therefore 4:8, which simplifies to 1:2.

**Conclusion for Step 1**: Statement 1 is correct.

### Step 2: Analyze Statement 2
**Statement 2**: In ZnS, `Zn^2+` ions occupy alternate tetrahedral voids, and in `CaF_2`, `F^(-)` ions occupy all the tetrahedral voids of the FCC unit cell.

- This statement describes the arrangement of ions in both structures accurately. In ZnS, `Zn^2+` does occupy alternate tetrahedral voids, and in CaF2, all tetrahedral voids are indeed occupied by `F^(-)` ions.

**Conclusion for Step 2**: Statement 2 is also correct.

### Step 3: Relationship Between the Statements
Statement 2 provides a correct explanation for Statement 1. The arrangement of ions in both structures directly leads to the ratio of `Zn^2+` to `F^(-)` being 1:2.

### Final Conclusion
Both statements are correct, and Statement 2 is the correct explanation for Statement 1.

### Final Answer
Both statements are true, and Statement 2 correctly explains Statement 1.

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