Which of the following sulphates have the highest solubility in water ?

Options

A. `BeSO_(4)`
B. `MgSO_(4)`
C. `BaSO_(4)`
D. `CaSO_(4)`

Answer

To determine which sulfate has the highest solubility in water among the given options (BeSO4, MgSO4, BaSO4, and CaSO4), we can analyze the solubility based on lattice energy and hydration energy.

### Step-by-Step Solution:

1. **Understanding Solubility**:
- Solubility of a salt in water is influenced by two main factors: lattice energy and hydration energy.
- Lattice energy is the energy required to separate one mole of a solid ionic compound into its gaseous ions.
- Hydration energy is the energy released when ions are surrounded by water molecules.

2. **Analyzing the Compounds**:
- The compounds we are considering are:
- BeSO4 (Beryllium sulfate)
- MgSO4 (Magnesium sulfate)
- BaSO4 (Barium sulfate)
- CaSO4 (Calcium sulfate)

3. **Lattice Energy Consideration**:
- As we move from BeSO4 to BaSO4, the size of the cation increases (Be < Mg < Ca < Ba).
- Larger cations generally lead to lower lattice energy because the distance between the ions increases, reducing the electrostatic attraction.

4. **Hydration Energy Consideration**:
- Hydration energy decreases as the size of the cation increases.
- Beryllium (Be) has the highest hydration energy due to its small size, followed by magnesium (Mg), calcium (Ca), and then barium (Ba).

5. **Comparing Solubility**:
- For BeSO4, the high hydration energy compensates for its relatively high lattice energy, leading to good solubility.
- MgSO4 also has good solubility, but not as high as BeSO4.
- BaSO4 has low solubility due to its low hydration energy and high lattice energy.
- CaSO4 has moderate solubility, but still lower than BeSO4.

6. **Conclusion**:
- Based on the analysis, BeSO4 has the highest solubility in water compared to the other sulfates listed.

### Final Answer:
The sulfate with the highest solubility in water is **BeSO4** (Beryllium sulfate).

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