Which one of the following is the most easily soluble in water?

Options

A. `SrCO_4`
B. `BaSO_4`
C. `BeSO_4`
D. `CaSO_4`

Answer

To determine which of the following compounds is the most easily soluble in water, we need to analyze the solubility of the group 2 sulfates. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Group 2 Sulfates
The group 2 sulfates we need to consider include:
- Beryllium sulfate (BeSO₄)
- Magnesium sulfate (MgSO₄)
- Calcium sulfate (CaSO₄)
- Strontium sulfate (SrSO₄)
- Barium sulfate (BaSO₄)

### Step 2: Understand Solubility Trends
The solubility of group 2 sulfates generally decreases as we move down the group from beryllium to barium. This is due to the increasing size of the cations, which affects the hydration energy.

### Step 3: Analyze Hydration Energy
Hydration energy is the energy released when ions are surrounded by water molecules. As the size of the cation increases (moving from Be²⁺ to Ba²⁺), the hydration energy decreases. This is because larger ions are less effectively surrounded by water molecules compared to smaller ions.

### Step 4: Relate Hydration Energy to Solubility
Since solubility is directly related to hydration energy (higher hydration energy means higher solubility), the decreasing hydration energy as we move down the group results in decreased solubility of the sulfates.

### Step 5: Identify the Most Soluble Sulfate
Given the trend, beryllium sulfate (BeSO₄) is expected to be the most soluble sulfate among the group 2 sulfates, followed by magnesium sulfate (MgSO₄), and then calcium sulfate (CaSO₄), which is sparingly soluble. Strontium sulfate (SrSO₄) and barium sulfate (BaSO₄) are largely insoluble.

### Conclusion
Therefore, the most easily soluble sulfate in water among the group 2 sulfates is **Beryllium sulfate (BeSO₄)**.