Which of the following can act as buffer solution?

Options

A. `Na_(2)HPO_(4)+Na_(3)PO_(4)`
B. `H_(2)S+Na_(2)S`
C. `HCl+NaCl`
D. `NH_(4)OH+NH_(4)Cl`

Explanation

To determine which of the given options can act as a buffer solution, we need to identify pairs of conjugate acids and bases. A buffer solution is typically made from a weak acid and its conjugate base or a weak base and its conjugate acid. Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Option 1: Na2HPO4 and Na3PO4**
- Na2HPO4 can act as a weak acid (it can donate H⁺ ions).
- Na3PO4 can act as a weak base (it can accept H⁺ ions).
- Since we have both a weak acid and its conjugate base, this pair can form a buffer solution.
- **Conclusion for Option 1:** This can act as a buffer solution.

2. **Option 2: H2S and Na2S**
- H2S is a weak acid (it can donate H⁺ ions).
- Na2S can act as a weak base (it can accept H⁺ ions).
- Since we have both a weak acid and its conjugate base, this pair can also form a buffer solution.
- **Conclusion for Option 2:** This can act as a buffer solution.

3. **Option 3: HCl and NaCl**
- HCl is a strong acid (it completely dissociates in solution).
- NaCl does not provide a conjugate base to HCl.
- Since there is no weak acid and its conjugate base pair, this cannot act as a buffer solution.
- **Conclusion for Option 3:** This cannot act as a buffer solution.

4. **Option 4: NH4OH and NH4Cl**
- NH4OH is a weak base (it can accept H⁺ ions).
- NH4Cl can provide NH4⁺, which is the conjugate acid of NH4OH.
- Since we have both a weak base and its conjugate acid, this pair can form a buffer solution.
- **Conclusion for Option 4:** This can act as a buffer solution.

### Final Answer:
The options that can act as buffer solutions are:
- Option 1: Na2HPO4 and Na3PO4
- Option 2: H2S and Na2S
- Option 4: NH4OH and NH4Cl