The correct order of solubility of the sulphates of alkaline earth metals in water is

Options

A. `Be gt Ca gt Mg gt Ba gt Sr`
B. `Mg gt Be gt Ba gt Ca gt Sr`
C. `Be gt Mg gt Ca gt Sr gt Ba`
D. `Mg gt Ca gt Ba gt Be gt Sr`

Explanation

To determine the correct order of solubility of the sulphates of alkaline earth metals (Be, Mg, Ca, Sr, Ba) in water, we can analyze the trend based on the properties of these metals and their sulphates.

### Step-by-Step Solution:

1. **Identify the Alkaline Earth Metals**: The alkaline earth metals include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba).

2. **Understand Sulphate Solubility**: The solubility of sulphates in water generally decreases as we move down the group in the periodic table. This is due to the balance between the lattice energy of the sulphate salt and the hydration energy.

3. **Analyze Hydration Energy and Lattice Energy**:
- **Hydration Energy**: This is the energy released when ions are surrounded by water molecules. It tends to decrease down the group because the size of the metal ions increases, leading to a lower charge density.
- **Lattice Energy**: This is the energy required to separate one mole of a solid ionic compound into its gaseous ions. It generally increases down the group due to the larger size of the ions.

4. **Compare Solubility of Each Sulphate**:
- **Magnesium Sulphate (MgSO₄)**: Highly soluble in water due to relatively high hydration energy.
- **Calcium Sulphate (CaSO₄)**: Moderately soluble in water.
- **Strontium Sulphate (SrSO₄)**: Less soluble than calcium sulphate.
- **Barium Sulphate (BaSO₄)**: Very low solubility in water, often considered insoluble.

5. **Establish the Order of Solubility**: Based on the analysis:
- Most soluble: Magnesium Sulphate (MgSO₄)
- Next: Calcium Sulphate (CaSO₄)
- Followed by: Strontium Sulphate (SrSO₄)
- Least soluble: Barium Sulphate (BaSO₄)

6. **Final Order of Solubility**: Therefore, the correct order of solubility of the sulphates of alkaline earth metals in water is:
- **MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄**