Which one of the following salts will produce an alkaline solution while dissolving in water ?

Options

A. `NH_(4) Cl`
B. `Na_(2) CO_(3)`
C. `NaNO_(3)`
D. `Na_(2) SO_(4)`

Explanation

To determine which salt produces an alkaline solution when dissolved in water, we need to analyze the hydrolysis of each salt provided in the options. Let's go through each option step by step.

### Step 1: Analyze Ammonium Chloride (NH4Cl)
- **Dissolution Reaction**: When NH4Cl is dissolved in water, it dissociates into NH4⁺ and Cl⁻ ions.
- **Hydrolysis**: The NH4⁺ ion can react with water:
\[ NH4^+ + H2O \rightleftharpoons NH4OH + H^+ \]
- **Nature of Products**: NH4OH (ammonium hydroxide) is a weak base, and H⁺ ions indicate the presence of a strong acid (HCl). Since the solution contains a strong acid and a weak base, the solution will be acidic.

### Step 2: Analyze Sodium Carbonate (Na2CO3)
- **Dissolution Reaction**: When Na2CO3 is dissolved in water, it dissociates into Na⁺ and CO3²⁻ ions.
- **Hydrolysis**: The CO3²⁻ ion can react with water:
\[ CO3^{2-} + H2O \rightleftharpoons HCO3^- + OH^- \]
- **Nature of Products**: NaOH (sodium hydroxide) is a strong base, and HCO3⁻ is a weak acid. Since the solution contains a strong base and a weak acid, the solution will be alkaline.

### Step 3: Analyze Sodium Nitrate (NaNO3)
- **Dissolution Reaction**: When NaNO3 is dissolved in water, it dissociates into Na⁺ and NO3⁻ ions.
- **Hydrolysis**: The NO3⁻ ion does not hydrolyze significantly in water, and Na⁺ does not affect the pH.
- **Nature of Products**: Both NaOH and HNO3 (nitric acid) are strong, resulting in a neutral solution as the concentrations of H⁺ and OH⁻ ions will be equal.

### Step 4: Analyze Sodium Sulfate (Na2SO4)
- **Dissolution Reaction**: When Na2SO4 is dissolved in water, it dissociates into Na⁺ and SO4²⁻ ions.
- **Hydrolysis**: The SO4²⁻ ion does not hydrolyze significantly in water, similar to NO3⁻.
- **Nature of Products**: Both NaOH and H2SO4 (sulfuric acid) are strong, resulting in a neutral solution as the concentrations of H⁺ and OH⁻ ions will be equal.

### Conclusion
From the analysis, we find that:
- Ammonium chloride produces an acidic solution.
- Sodium carbonate produces an alkaline solution.
- Sodium nitrate and sodium sulfate produce neutral solutions.

Thus, the salt that produces an alkaline solution when dissolved in water is **Sodium Carbonate (Na2CO3)**.

### Final Answer
**Sodium Carbonate (Na2CO3)** produces an alkaline solution when dissolved in water.