The aqueous solution of which of the salts has pH close to `7` ?

Options

A. `FeCl_(3)`
B. `CH_(3)CO ON a`
C. `CH_(3)COONH_(4)`
D. `KCN`

Answer

To determine which salt has an aqueous solution with a pH close to 7, we need to analyze the behavior of different salts in water. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the nature of salts
Salts can be derived from strong acids and strong bases, weak acids and strong bases, strong acids and weak bases, or weak acids and weak bases. The pH of their solutions will vary based on the nature of the ions produced when they dissolve in water.

### Step 2: Analyze the given salts
1. **FeCl3 (Iron(III) chloride)**:
- Dissociates into Fe³⁺ and Cl⁻ ions.
- Fe³⁺ can hydrolyze in water to form HCl, which is a strong acid. This will lower the pH (pH < 7).

2. **CH3COONa (Sodium acetate)**:
- Dissociates into CH3COO⁻ and Na⁺ ions.
- CH3COO⁻ (acetate ion) is the conjugate base of acetic acid (a weak acid) and will increase the pH (pH > 7).

3. **CH3COONH4 (Ammonium acetate)**:
- Dissociates into CH3COO⁻ and NH4⁺ ions.
- CH3COO⁻ (acetate ion) is a weak base, and NH4⁺ (ammonium ion) is a weak acid. The weak acid and weak base will create a solution that is close to neutral (pH ≈ 7).

4. **KOH (Potassium hydroxide)**:
- Dissociates into K⁺ and OH⁻ ions.
- KOH is a strong base, which will result in a high pH (pH > 7).

### Step 3: Conclusion
Among the salts analyzed, **CH3COONH4 (Ammonium acetate)** is the only salt that will produce a solution with a pH close to 7 because it contains both a weak acid and a weak base.

### Final Answer
The aqueous solution of **CH3COONH4 (Ammonium acetate)** has a pH close to 7.

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