Out of the following , which pair of solutions is not a buffer solution ?

Options

A. `NH_(4)Cl + NH_(4)OH`
B. `NaCl + NH_(4)OH`
C. `Na_(2)HPO_(4) + Na_(3)PO_(4)`
D. `CH_(3)COOH + CH_(3)COONa`

Answer

To determine which pair of solutions is not a buffer solution, we need to understand what constitutes a buffer solution. A buffer solution is one that resists changes in pH upon the addition of small amounts of acid or base. There are two types of buffer solutions:

1. **Acidic Buffer**: Made from a weak acid and its salt (conjugate base).
2. **Basic Buffer**: Made from a weak base and its salt (conjugate acid).

Now, let's analyze the given pairs of solutions to identify which one does not form a buffer.

### Step-by-Step Solution

1. **Identify the pairs of solutions**: We need to look at the pairs provided in the question.

2. **Analyze each pair**:
- **Pair 1: NH4OH and NH4Cl**:
- NH4OH is a weak base, and NH4Cl is the salt formed from this weak base and a strong acid (HCl). This is a basic buffer.
- **Pair 2: NaOH and NaCl**:
- NaOH is a strong base, and NaCl is a salt formed from a strong acid (HCl) and a strong base (NaOH). This does not form a buffer solution because both components are strong.
- **Pair 3: Sodium phosphate (Na3PO4) and H3PO4**:
- H3PO4 is a weak acid, and sodium phosphate is a salt formed from a weak acid and a strong base. This forms an acidic buffer.
- **Pair 4: CH3COOH (acetic acid) and NaOH**:
- CH3COOH is a weak acid, and NaOH is a strong base. This combination also forms an acidic buffer.

3. **Conclusion**:
- The only pair that does not form a buffer solution is **Pair 2: NaOH and NaCl** because both components are from strong acids and bases, which do not provide the necessary weak component to resist pH changes.

### Final Answer
The pair of solutions that is not a buffer solution is **NaOH and NaCl**.