Which among the following is an acidic buffer?

Options

A. `CH_3COOH + HCI`
B. `CH_3COOH + CH_3COONa`
C. `HCI + H_2SO_4`
D. `NH_4OH + NaOH`

Answer

To determine which among the given options is an acidic buffer, we need to understand the definition and components of an acidic buffer. An acidic buffer is composed of a weak acid and its conjugate base. Let's go through the steps to identify the acidic buffer from the options provided.

### Step-by-Step Solution:

1. **Understand the Definition of an Acidic Buffer**:
- An acidic buffer consists of a weak acid and its conjugate base. The weak acid can partially dissociate in solution, while the conjugate base can react with any added acids to maintain the pH.

2. **Identify the Options**:
- We need to look at the options provided (though not listed here, we will assume common examples like HCl, CH3COOH, NaO, etc.).

3. **Evaluate Each Option**:
- **Option 1**: If it contains a strong acid (e.g., HCl), it cannot be an acidic buffer. Strong acids completely dissociate and do not provide the necessary equilibrium for buffering.
- **Option 2**: If it contains a weak acid (e.g., CH3COOH) and its conjugate base (e.g., sodium acetate, CH3COONa), this option is likely an acidic buffer. Sodium acetate dissociates in solution to give acetate ions, which are the conjugate base of acetic acid.
- **Option 3**: If it contains a strong base (e.g., NaOH), it cannot be an acidic buffer. Similar to strong acids, strong bases do not provide the necessary equilibrium for buffering.
- **Option 4**: If it contains a weak base and its conjugate acid, it would be a basic buffer, not an acidic buffer.

4. **Conclusion**:
- Based on the evaluation, the option that contains a weak acid and its conjugate base is the correct answer. For example, if the option is sodium acetate (CH3COONa) with acetic acid (CH3COOH), then this is an acidic buffer.

### Final Answer:
The correct option that represents an acidic buffer is the one containing a weak acid (like CH3COOH) and its conjugate base (like sodium acetate).