Assertion: The fluorides of alkaline earth metals are relatively less soluble than chlorides.
Reason: Fluorides have high latttice energies.

Options

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

Answer

To solve the assertion-reason question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the fluorides of alkaline earth metals are relatively less soluble than their chlorides.
- This means that when comparing the solubility of alkaline earth metal fluorides (like BeF2, MgF2, etc.) with their corresponding chlorides (like BeCl2, MgCl2, etc.), the fluorides are less soluble in water.

2. **Understanding the Reason**:
- The reason given is that fluorides have high lattice energies.
- Lattice energy refers to the energy released when gaseous ions combine to form an ionic solid. Higher lattice energy indicates that the ions are held together more tightly in the solid state, making it harder for them to separate and dissolve in water.

3. **Analyzing Lattice Energy**:
- For alkaline earth metal compounds, lattice energy is influenced by the charges of the ions and the sizes of the ions involved.
- Both fluorides and chlorides of alkaline earth metals have the same cation (the alkaline earth metal) but differ in their anions (F- vs. Cl-).
- Fluoride ions (F-) are smaller than chloride ions (Cl-), which results in a higher lattice energy for fluorides compared to chlorides.

4. **Comparing Hydration Energy**:
- Hydration energy is the energy released when ions are surrounded by water molecules.
- If the hydration energy is greater than the lattice energy, the compound will be soluble in water.
- Since fluorides have higher lattice energies than chlorides, their hydration energies are not sufficient to overcome this lattice energy, leading to lower solubility.

5. **Conclusion**:
- Both the assertion and reason are true: the fluorides of alkaline earth metals are indeed less soluble than their chlorides due to the higher lattice energies of the fluorides.
- Therefore, the assertion is correct, and the reason correctly explains why the assertion is true.

### Final Answer:
Both the assertion and the reason are true, and the reason correctly explains the assertion.