Which of the following has max. solubility at low pH?

Options

A. `NH_(4)Cl`
B. `NaCl`
C. `Na_(3)PO_(4)`
D. `Sr(OH)_(2)`

Explanation

To determine which of the following compounds has the maximum solubility at low pH, we need to analyze the nature of each compound in relation to acidity and basicity.

### Step-by-Step Solution:

1. **Understanding Low pH**:
- Low pH indicates an acidic environment, which means there is a high concentration of H⁺ ions in the solution.

2. **Analyzing Each Compound**:
- **Ammonium Chloride (NH₄Cl)**:
- This is a salt formed from a strong acid (HCl) and a weak base (NH₄OH). In acidic conditions, it remains soluble but does not significantly increase solubility due to the weak base.
- **Sodium Chloride (NaCl)**:
- This is a neutral salt formed from a strong acid (HCl) and a strong base (NaOH). Its solubility does not change significantly in acidic conditions.
- **Phosphoric Acid (H₃PO₄)**:
- This is a weak acid and does not significantly increase solubility in acidic conditions.
- **Strontium Hydroxide (Sr(OH)₂)**:
- This is a strong base. In acidic conditions, it will react with H⁺ ions to form strontium ions and water, thus increasing its solubility.

3. **Conclusion**:
- Among the given options, **Strontium Hydroxide (Sr(OH)₂)** is the most basic compound and will react with the H⁺ ions present in the acidic solution, leading to maximum solubility. Therefore, the correct answer is **D) Strontium Hydroxide**.