Which of the following is (are) correct for buffer solution?

Options

A. Acidic buffer will be effective within in the `pH` range `(pK_(a) +-1)`.
B. Basic buffer will be effective within the `pH` range `(pK_(w)-pK_(b)+-1)`.
C. `H_(3)PO_(4)+NaH_(2)PO_(4)`is not a buffer solution.
D. Buffers behave most effectively when the `["Salt"]//["Acid"]`

Explanation

To determine which statements are correct regarding buffer solutions, we can analyze the properties and characteristics of buffer solutions step by step.

### Step-by-Step Solution:

1. **Definition of Buffer Solution**:
- A buffer solution is a solution that resists changes in pH upon the addition of small amounts of an acid or a base. This property is crucial for maintaining a stable pH in various chemical and biological processes.

2. **Types of Buffer Solutions**:
- There are two main types of buffer solutions:
- **Acidic Buffers**: These consist of a weak acid and its salt (conjugate base).
- **Basic Buffers**: These consist of a weak base and its salt (conjugate acid).

3. **Effective pH Range**:
- The effectiveness of a buffer solution is often described in terms of its pH range. For an acidic buffer, the effective pH range is given by:
- \( pH = pKa \pm 1 \)
- For a basic buffer, the effective pH range can be expressed as:
- \( pH = pKw - pKb \pm 1 \)

4. **Buffer Capacity**:
- Buffer capacity refers to the ability of a buffer solution to resist changes in pH. It is defined as the amount of acid or base (in moles) that must be added to one liter of buffer solution to change the pH by one unit.

5. **Salt-to-Acid Ratio**:
- Buffers behave most effectively when the ratio of the concentration of salt to the concentration of the weak acid (or weak base) is equal to 1. This means:
- When the salt-to-acid ratio is 1, the pH of the buffer solution is equal to the pKa of the weak acid.

6. **Examples of Buffer Solutions**:
- An example of an acidic buffer is a solution containing phosphoric acid (H3PO4) and its salt sodium dihydrogen phosphate (NaH2PO4). This combination forms an effective acidic buffer.

7. **Evaluating Statements**:
- **Statement 1**: "Acidic buffer will be effective within the pH range \( pKa \pm 1 \)" - **Correct**
- **Statement 2**: "H3PO4 + NaH2PO4 is not a buffer solution" - **Incorrect** (it is a buffer solution)
- **Statement 3**: "Buffers behave most effectively when the salt-to-acid ratio is 1" - **Correct**

### Conclusion:
Based on the analysis:
- The correct statements regarding buffer solutions are:
- Acidic buffers are effective within the pH range \( pKa \pm 1 \).
- Buffers behave most effectively when the salt-to-acid ratio is 1.