The salt having the least solubility in water is :

Options

A. `BaCl_(2)`
B. `Ba(NO_(3))_(2)`
C. `MgSO_(4)`
D. `BaSO_(4)`

Answer

To determine which salt has the least solubility in water among the given options (barium chloride, barium nitrate, magnesium sulfate, and barium sulfate), we can analyze the solubility of each salt.

### Step-by-Step Solution:

1. **Identify the salts**: The salts provided are:
- Barium chloride (BaCl₂)
- Barium nitrate (Ba(NO₃)₂)
- Magnesium sulfate (MgSO₄)
- Barium sulfate (BaSO₄)

2. **Research solubility**: Check the solubility of each salt in water:
- **Barium chloride (BaCl₂)**: This salt is soluble in water. When dissolved, it dissociates into barium ions (Ba²⁺) and chloride ions (Cl⁻).
- **Barium nitrate (Ba(NO₃)₂)**: This salt is also soluble in water. It dissociates into barium ions (Ba²⁺) and nitrate ions (NO₃⁻).
- **Magnesium sulfate (MgSO₄)**: This salt is soluble in water and dissociates into magnesium ions (Mg²⁺) and sulfate ions (SO₄²⁻).
- **Barium sulfate (BaSO₄)**: This salt is known to be insoluble in water. It forms a precipitate when barium ions react with sulfate ions.

3. **Compare solubility**: Based on the solubility data:
- Barium chloride, barium nitrate, and magnesium sulfate are soluble in water.
- Barium sulfate is insoluble and forms a precipitate.

4. **Conclusion**: Among the salts listed, barium sulfate (BaSO₄) has the least solubility in water. Therefore, the answer is:
- **Barium sulfate (BaSO₄)** is the salt with the least solubility in water.

### Final Answer:
The salt having the least solubility in water is **Barium sulfate (BaSO₄)**.

---