Sodium sulphate is soluble in water,whereas barium sulphate is sparingly soluble because

Options

A. the hydration energy of sodium sulphate is more than its lattice energy
B. the lattice energy of barium sulphate is more than its hydriation energy
C. the lattice energy has no role to play in solubility
D. the hydration energy of sodium sulphate is less than its lattice energy.

Explanation

To understand why sodium sulfate is soluble in water while barium sulfate is sparingly soluble, we need to analyze the concepts of lattice energy and hydration energy.

### Step-by-Step Solution:

1. **Definition of Lattice Energy**:
Lattice energy is the energy required to separate one mole of a solid ionic compound into its gaseous ions. It is a measure of the strength of the forces between the ions in an ionic solid. Higher lattice energy indicates stronger ionic bonds.

2. **Definition of Hydration Energy**:
Hydration energy is the energy released when ions are surrounded by water molecules and solvate (or hydrate) in solution. This energy is crucial for the dissolution process because it compensates for the energy required to break the ionic bonds in the solid.

3. **Dissolution Process**:
When an ionic compound dissolves in water, it undergoes two main steps:
- The ionic solid dissociates into its constituent ions (this requires energy equal to the lattice energy).
- The ions are then surrounded by water molecules, releasing hydration energy.

4. **Energy Relationship**:
For a salt to be soluble in water, the overall enthalpy change (ΔH) for the dissolution process must be negative (exothermic). This can be expressed as:
\[ \Delta H = \text{Lattice Energy} + \text{Hydration Energy} \]
For the dissolution to be spontaneous, the hydration energy must be greater than the lattice energy:
\[ \text{Hydration Energy} > \text{Lattice Energy} \]

5. **Comparison of Sodium Sulfate and Barium Sulfate**:
- **Sodium Sulfate (Na2SO4)**: The hydration energy of sodium ions is significantly high, which compensates for the lattice energy, making sodium sulfate soluble in water.
- **Barium Sulfate (BaSO4)**: Barium sulfate has a much higher lattice energy compared to its hydration energy. This means that the energy required to break the ionic bonds in barium sulfate is not compensated by the energy released during hydration, resulting in its sparing solubility.

6. **Conclusion**:
Therefore, the solubility of sodium sulfate in water is due to its higher hydration energy compared to its lattice energy, while barium sulfate is sparingly soluble because its lattice energy exceeds its hydration energy.

### Final Answer:
- Sodium sulfate is soluble in water because its hydration energy is greater than its lattice energy.
- Barium sulfate is sparingly soluble because its lattice energy is greater than its hydration energy.