To obtain a buffer wich should be suitable for maintaining a pH of about 4-5, we need to have in solution, a mixture of

Options

A. A strong base + its salt with a weak acid
B. A weak base + its salt with a strong acid
C. A strong acid + its salt with a weak base
D. A weak acid + its salt with a strong base

Explanation

To obtain a buffer solution suitable for maintaining a pH of about 4-5, we need to follow these steps:

### Step-by-Step Solution:

1. **Understanding Buffer Solutions**:
- A buffer solution is designed to resist changes in pH when small amounts of acid or base are added. There are two types of buffer solutions: acidic buffers and basic buffers.

2. **Identifying the Type of Buffer Needed**:
- Since we want to maintain a pH of 4-5, we need an acidic buffer. Acidic buffers are composed of a weak acid and its conjugate base.

3. **Choosing the Components**:
- For an acidic buffer, we need to select a weak acid. Common examples of weak acids include acetic acid (CH₃COOH) and formic acid (HCOOH).
- The conjugate base of the weak acid will be a salt formed with a strong base. For example, if we choose acetic acid as our weak acid, its conjugate base would be sodium acetate (CH₃COONa).

4. **Finalizing the Buffer Composition**:
- Therefore, to prepare a buffer solution with a pH of 4-5, we can mix a weak acid (like acetic acid) with its conjugate base (like sodium acetate).

5. **Conclusion**:
- The correct mixture for a buffer solution suitable for maintaining a pH of about 4-5 is a weak acid and its salt with a strong base.