Which of the following will function as buffer ?

Options

A. NaCl+NaOH
B. Borax + boric acid
C. `NaH_(2)PO_(4)+Na_(2)HPO_(4)`
D. `NH_(4)Cl+NH_(4)OH`

Answer

To determine which of the given options will function as a buffer, we need to understand the concept 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**:
- We need to analyze the provided options to see if they consist of a weak acid and its conjugate base or a weak base and its conjugate acid.

2. **Evaluate NaCl**:
- NaCl is a salt derived from a strong acid (HCl) and a strong base (NaOH). It does not contain a weak acid or a weak base, so it cannot function as a buffer.

3. **Evaluate NaOH**:
- NaOH is a strong base and does not have a corresponding weak acid to form a buffer solution. Therefore, it cannot function as a buffer.

4. **Evaluate H3BO3 (Boric Acid)**:
- Boric acid (H3BO3) is a weak acid, but it does not have a corresponding conjugate base that is present in the solution. Thus, it cannot function as a buffer.

5. **Evaluate NaH2PO4**:
- NaH2PO4 contains the weak acid H2PO4⁻. Its conjugate base is HPO4²⁻. Since this pair (weak acid and its conjugate base) is present, NaH2PO4 can function as a buffer.

6. **Evaluate NH4Cl**:
- NH4Cl contains NH4⁺, which is the conjugate acid of the weak base ammonia (NH3). However, since ammonia is not present in the solution, NH4Cl alone cannot function as a buffer.

### Conclusion:
Among the options provided, **NaH2PO4** is the only one that can function as a buffer.