Which of the following can form buffer solution?

Options

A. `aq. NH _(3) + NH _(4) OH`
B. `KOH + HNO 3`
C. `NaOH + HCl `
D. `KI + KOH`

Answer

To determine which of the given options can form a buffer solution, we need to understand the definition of a buffer solution. A buffer solution is typically made up of a weak acid and its conjugate base or a weak base and its conjugate acid.

### Step-by-step Solution:

1. **Identify the Components of Each Option**:
- **Option 1**: Aqueous Ammonia (NH3) and Ammonium Hydroxide (NH4OH)
- **Option 2**: Potassium Hydroxide (KOH) and Nitric Acid (HNO3)
- **Option 3**: Sodium Hydroxide (NaOH) and Hydrochloric Acid (HCl)
- **Option 4**: Potassium Iodide (KI) and Potassium Hydroxide (KOH)

2. **Analyze Option 1**:
- Aqueous Ammonia (NH3) is a weak base.
- Ammonium Hydroxide (NH4OH) can be viewed as the solution of NH3 in water, which dissociates into NH4+ (the conjugate acid) and OH- (the base).
- Since this option contains a weak base (NH3) and its conjugate acid (NH4+), it can form a buffer solution.

3. **Analyze Option 2**:
- KOH is a strong base and HNO3 is a strong acid.
- The combination of a strong acid and a strong base does not form a buffer solution.

4. **Analyze Option 3**:
- NaOH is a strong base and HCl is a strong acid.
- Similar to Option 2, this combination does not form a buffer solution.

5. **Analyze Option 4**:
- KI is a salt, and KOH is a strong base.
- A strong base and its salt do not form a buffer solution.

6. **Conclusion**:
- The only option that can form a buffer solution is **Option 1: Aqueous Ammonia and Ammonium Hydroxide**.

### Final Answer:
The correct option that can form a buffer solution is **Option 1: Aqueous Ammonia and Ammonium Hydroxide**.

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