The solublity of hydroides, fluorides of oxalates of the metals of Group IIA

Options

A. increases down the group.
B. decreases down the group.
C. varies randomly.
D. is constant.

Explanation

To solve the question regarding the solubility of hydrides, fluorides, and oxalates of the metals of Group IIA (alkaline earth metals), we need to analyze the factors that affect solubility: lattice energy and hydration energy.

### Step-by-Step Solution:

1. **Understanding Lattice Energy**:
- Lattice energy is the energy required to separate one mole of an ionic solid into its gaseous ions. It is influenced by the charge and size of the ions involved.
- For Group IIA metals, as we move down the group, the size of the metal ions increases (e.g., from Be²⁺ to Ba²⁺).

**Hint**: Remember that larger ions generally lead to lower lattice energy due to increased distance between ions.

2. **Understanding Hydration Energy**:
- Hydration energy (or hydration enthalpy) is the energy released when one mole of gaseous ions is surrounded by water molecules and solvated.
- As the size of the metal ions increases down the group, the hydration energy generally decreases because larger ions are less effectively solvated by water.

**Hint**: Consider how the size of the ion affects its interaction with water molecules.

3. **Comparing Lattice Energy and Hydration Energy**:
- For Group IIA metals, as we move down the group, the lattice energy decreases due to the increasing size of the metal ions.
- At the same time, the hydration energy also decreases but at a different rate.

**Hint**: Think about how the balance between these two energies affects solubility.

4. **Conclusion on Solubility**:
- The overall solubility of hydrides, fluorides, and oxalates of Group IIA metals tends to increase down the group. This is because the decrease in lattice energy outweighs the decrease in hydration energy, leading to a net increase in solubility.

**Hint**: Remember that the trend in solubility is a result of the interplay between lattice and hydration energies.

### Final Answer:
The solubility of hydrides, fluorides, and oxalates of the metals of Group IIA increases down the group.