Which of these is not a buffer solution ?

Options

A. `NH_(4)Cl + NH_(4)OH`
B. `CH_(3)COOH + CH_(3)COONa`
C. `CH_(3)COONH_(4)`
D. Borax `+` Boric acid

Answer

To determine which of the given options is not a buffer solution, we need to understand the characteristics of buffer solutions and analyze each option accordingly.

### Step-by-Step Solution:

1. **Understand Buffer Solutions**:
- 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:
- **Acidic Buffer**: Formed from a weak acid and its conjugate base (salt).
- **Basic Buffer**: Formed from a weak base and its conjugate acid (salt).

2. **Analyze Each Option**:
- **Option 1: NH4Cl and NH4OH**
- NH4OH is a weak base.
- NH4Cl is the conjugate acid of NH4OH (formed from a weak base and a strong acid).
- Therefore, this combination forms a basic buffer solution.

- **Option 2: Acetic Acid and Sodium Acetate**
- Acetic acid (CH3COOH) is a weak acid.
- Sodium acetate (CH3COONa) is the conjugate base of acetic acid.
- This combination forms an acidic buffer solution.

- **Option 3: CH3COONH4**
- This salt is formed from a weak acid (acetic acid) and a weak base (NH4OH).
- Since it is a combination of a weak acid and a weak base, it does not form a buffer solution.

- **Option 4: Borax and Boric Acid**
- Boric acid (H3BO3) is a weak acid.
- Borax (Na2B4O5(OH)4·8H2O) acts as a salt derived from a weak acid and a strong base (NaOH).
- Therefore, this combination forms an acidic buffer solution.

3. **Conclusion**:
- The combination that does not form a buffer solution is **Option 3: CH3COONH4**.

### Final Answer:
**Option 3: CH3COONH4 is not a buffer solution.**

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