A number of ionic compounds are insoluble in water. This is because

Options

A. Ionic compounds do not dissolve in water
B. Water has a high dielectric constant
C. Water is not a good ionizing solvent
D. These molecules have high lattice energy

Answer

### Step-by-Step Solution:

1. **Understanding Ionic Compounds**: Ionic compounds are formed by the electrostatic attraction between positively and negatively charged ions. They typically have a crystalline structure.

2. **Dissolution in Water**: For an ionic compound to dissolve in water, the energy released when the ions are hydrated (hydration energy) must be greater than the energy required to separate the ions from the lattice (lattice energy).

3. **Lattice Energy**: Lattice energy is the energy required to break apart the ionic lattice into individual gaseous ions. Ionic compounds with high lattice energy have strong attractive forces holding the ions together.

4. **Hydration Energy**: Hydration energy is the energy released when water molecules surround and stabilize the separated ions. If the hydration energy is not sufficient to overcome the lattice energy, the compound will not dissolve.

5. **Comparison of Energies**: If the lattice energy of an ionic compound is greater than its hydration energy, the compound will remain insoluble in water. This is because the energy required to break the ionic bonds is higher than the energy gained from hydration.

6. **Conclusion**: Therefore, the reason why some ionic compounds are insoluble in water is that they have high lattice energy, which is greater than the hydration energy.

### Final Answer:
A number of ionic compounds are insoluble in water because they have high lattice energy, which is greater than the hydration energy.

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