pH of the following solution is not affected by dilution

Options

A. 0.01M `NaHCO_(3)^(-)`
B. 0.01 M `NaH_(2)PO_(4)`
C. 0.01 M `CH_(3)COONH_(4)`
D. All of these

Explanation

To determine which solution's pH is not affected by dilution, we need to analyze the nature of each solution provided in the options: NaHCO3, NaH2PO4, and CH3COONH4.

### Step-by-Step Solution:

1. **Understanding Buffer Solutions**:
- A buffer solution is one that can resist changes in pH upon the addition of small amounts of acid or base, or upon dilution. Buffers typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid.

2. **Analyzing Each Solution**:
- **NaHCO3 (Sodium Bicarbonate)**:
- NaHCO3 dissociates in water to give HCO3⁻ (bicarbonate ion), which is amphiprotic (can act as both an acid and a base).
- It can either accept a proton to form H2CO3 or donate a proton to form CO3²⁻. This property allows it to resist pH changes, making it a buffer solution.

- **NaH2PO4 (Sodium Dihydrogen Phosphate)**:
- NaH2PO4 dissociates to give H2PO4⁻ (dihydrogen phosphate ion), which is also amphiprotic.
- It can donate a proton to form HPO4²⁻ or accept a proton to form H3PO4. This also allows it to act as a buffer solution.

- **CH3COONH4 (Ammonium Acetate)**:
- CH3COONH4 dissociates to give CH3COO⁻ (acetate ion) and NH4⁺ (ammonium ion).
- The acetate ion can act as a weak base, while the ammonium ion can act as a weak acid. This combination allows it to resist changes in pH, thus functioning as a buffer solution.

3. **Conclusion**:
- All three solutions (NaHCO3, NaH2PO4, and CH3COONH4) can act as buffer solutions and resist changes in pH upon dilution. Therefore, the pH of all these solutions is not affected by dilution.

4. **Final Answer**:
- The correct answer is **Option D: All of these**.