Which of the following is least soluble in water?

Options

A. `MgSO_4`
B. `CaSO_4`
C. `BeSO_4`
D. `BaSO_4`

Answer

To determine which of the given compounds is least soluble in water, we can follow these steps:

### Step 1: Identify the Compounds
The question refers to compounds of the second group of the periodic table, specifically their sulfates. The compounds mentioned are:
- Beryllium sulfate (BeSO₄)
- Magnesium sulfate (MgSO₄)
- Calcium sulfate (CaSO₄)
- Strontium sulfate (SrSO₄)
- Barium sulfate (BaSO₄)

### Step 2: Understand the Solubility Trend
In general, the solubility of sulfates in water decreases as we move down the group in the periodic table. This is because the size of the metal ions increases, leading to a decrease in hydration energy, which is the energy released when ions are surrounded by water molecules.

### Step 3: Analyze the Compounds
- Beryllium sulfate (BeSO₄) is quite soluble in water.
- Magnesium sulfate (MgSO₄) is also soluble.
- Calcium sulfate (CaSO₄) has moderate solubility.
- Strontium sulfate (SrSO₄) is less soluble than calcium sulfate.
- Barium sulfate (BaSO₄) is known to be very poorly soluble in water.

### Step 4: Conclusion
Based on the trend of solubility in sulfates of alkaline earth metals, we conclude that barium sulfate (BaSO₄) is the least soluble in water among the given options.

### Final Answer
The least soluble sulfate in water is **Barium sulfate (BaSO₄)**.

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