For the buffer solution containing `NH_(4)OH` and `NH_(4)Cl, P^(H)` of the buffer solution can be increased by

Options

A. Adding some more `H_(2)O`
B. Adding some more `NH_(4)OH`
C. Removing `NH_(4)Cl`
D. Both 2 and 3

Explanation

To solve the problem of how to increase the pH of a buffer solution containing \( NH_4OH \) (ammonium hydroxide) and \( NH_4Cl \) (ammonium chloride), we can follow these steps:

### Step 1: Understand the Components of the Buffer
The buffer solution consists of a weak base \( NH_4OH \) and its conjugate acid \( NH_4Cl \). The pH of a buffer solution is determined by the concentrations of the weak base and its conjugate acid.

### Step 2: Recall the Henderson-Hasselbalch Equation
For a basic buffer, the pH can be expressed using the Henderson-Hasselbalch equation:
\[ pH = pK_b + \log\left(\frac{[Salt]}{[Base]}\right) \]
Where:
- \( pK_b \) is the negative logarithm of the base dissociation constant of the weak base.
- \([Salt]\) is the concentration of the conjugate acid (\( NH_4Cl \)).
- \([Base]\) is the concentration of the weak base (\( NH_4OH \)).

### Step 3: Analyze the Relationship Between pH, Salt, and Base Concentrations
From the equation, we can see that:
- The pH is directly proportional to the concentration of the base (\( NH_4OH \)).
- The pH is inversely proportional to the concentration of the salt (\( NH_4Cl \)).

### Step 4: Determine How to Increase pH
To increase the pH of the buffer solution, we can:
1. **Increase the concentration of the base** (\( NH_4OH \)): This will increase the pH because it will increase the logarithmic term in the equation.
2. **Decrease the concentration of the salt** (\( NH_4Cl \)): This will also increase the pH because it will decrease the logarithmic term in the equation.

### Step 5: Evaluate the Options
Based on the analysis:
- Adding water will dilute the solution but will not specifically increase the pH.
- Adding more base (\( NH_4OH \)) will increase the pH.
- Removing some salt (\( NH_4Cl \)) will also increase the pH.

Thus, both adding base and removing salt will effectively increase the pH of the buffer solution.

### Conclusion
The correct answer is that the pH of the buffer solution can be increased by either adding base or removing salt. Therefore, the answer is:
**Option 4: Both 2 and 3.**

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