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 nature of each salt and the resulting solution it forms. An alkaline solution is typically produced when a strong base reacts with a weak acid, resulting in a basic salt.

### Step-by-Step Solution:

1. **Understanding Alkaline Solutions**:
- An alkaline solution is formed when a salt derived from a strong base and a weak acid is dissolved in water. This results in a solution with a pH greater than 7.

2. **Analyzing Each Option**:
- **Option 1: Ammonium Chloride (NH4Cl)**:
- When dissolved in water, it dissociates into NH4+ and Cl- ions.
- NH4+ is the conjugate acid of the weak base ammonia (NH3), and Cl- is the conjugate base of the strong acid HCl.
- The solution will be acidic due to the presence of NH4+, so this option does not produce an alkaline solution.

- **Option 2: Sodium Carbonate (Na2CO3)**:
- When dissolved in water, it dissociates into 2 Na+ ions and CO3^2- ions.
- CO3^2- can react with water to produce OH- ions (hydroxide ions), making the solution basic:
\[ CO3^{2-} + H2O \rightleftharpoons HCO3^{-} + OH^{-} \]
- Since Na2CO3 is derived from a strong base (NaOH) and a weak acid (H2CO3), it produces an alkaline solution. This option is correct.

- **Option 3: Sodium Nitrate (NaNO3)**:
- When dissolved in water, it dissociates into Na+ and NO3- ions.
- Both Na+ and NO3- are derived from strong acid (HNO3) and strong base (NaOH), resulting in a neutral solution. Thus, it does not produce an alkaline solution.

- **Option 4: Sodium Sulfate (Na2SO4)**:
- When dissolved in water, it dissociates into 2 Na+ and SO4^2- ions.
- Similar to sodium nitrate, both ions are derived from a strong base (NaOH) and a strong acid (H2SO4), resulting in a neutral solution. Therefore, it does not produce an alkaline solution.

3. **Conclusion**:
- After analyzing all options, **sodium carbonate (Na2CO3)** is the only salt that produces an alkaline solution when dissolved in water.

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