Assertion LiF is practically insoluble in water
Reasoning LiF has very high lattice energy .

Options

A. If both `(A)` and `(R )` are correct and `(R )` is the correct
explanation of `(A)`
B. If both `(A)` and `(R )` are correct and `(R )` is the correct
explanation of `(A)`
C. If `(A)` is correct but `(R )` is incorrect
D. If `(A)` is incorrect but `(R )` is correct

Answer

To solve the assertion and reasoning question regarding the solubility of lithium fluoride (LiF) in water, we will analyze both the assertion and the reasoning step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "LiF is practically insoluble in water."
- This means that when LiF is added to water, it does not dissolve significantly.

2. **Understanding the Reasoning**:
- The reasoning states that "LiF has very high lattice energy."
- Lattice energy is the energy released when gaseous ions come together to form a solid ionic compound. A high lattice energy indicates that the ions are held together very tightly in the solid state.

3. **Analyzing the Ionic Nature of LiF**:
- LiF consists of lithium ions (Li⁺) and fluoride ions (F⁻).
- Both ions are relatively small in size, which allows them to form a strong ionic bond.

4. **Comparing Lattice Energy and Hydration Energy**:
- When LiF is placed in water, the water molecules attempt to surround and separate the Li⁺ and F⁻ ions. This process requires energy, known as hydration energy.
- For LiF, the lattice energy is very high due to the small size of the ions, leading to a strong attraction between them.
- The hydration energy for LiF is comparatively low because the small size of the ions does not allow water molecules to effectively solvate them.

5. **Conclusion on Solubility**:
- Since the lattice energy of LiF is much greater than the hydration energy, the energy required to break the ionic bonds in LiF is not compensated by the energy released during hydration.
- Therefore, LiF remains largely insoluble in water.

6. **Final Evaluation**:
- Both the assertion and the reasoning are correct. The reasoning provides a valid explanation for the assertion because the high lattice energy of LiF is the primary reason for its low solubility in water.

### Final Answer:
Both the assertion and reasoning are correct, and the reasoning correctly explains the assertion.

---