In an acidic buffer solution, if some `H_(2)So_(4)` is added, its `pH` will

Options

A. Remain constant
B. Change but cannot be predicted
C. Decrease
D. Increase

Explanation

To determine how the pH of an acidic buffer solution changes when `H2SO4` is added, we can follow these steps:

### Step 1: Understand the Composition of an Acidic Buffer
An acidic buffer solution is typically made up of a weak acid and its conjugate salt. For example, a common acidic buffer is made from acetic acid (weak acid) and sodium acetate (conjugate salt).

**Hint:** Remember that an acidic buffer resists changes in pH when small amounts of acid or base are added.

### Step 2: Identify the Effect of Adding `H2SO4`
When `H2SO4`, a strong acid, is added to the acidic buffer, it increases the concentration of hydrogen ions (`H+`) in the solution. This leads to an increase in the concentration of the weak acid component of the buffer.

**Hint:** Consider how adding a strong acid affects the equilibrium of the buffer system.

### Step 3: Analyze the Buffer Equation
The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:
\[ \text{pH} = \text{pKa} + \log \left( \frac{[\text{Salt}]}{[\text{Acid}]} \right) \]

In this case:
- The concentration of the weak acid increases (let's denote it as `[\text{Acid}] + x` where `x` is the increase due to `H2SO4`).
- The concentration of the salt decreases (let's denote it as `[\text{Salt}] - y` where `y` is the decrease due to the shift in equilibrium).

**Hint:** Think about how changes in the concentrations of the acid and salt affect the log term in the equation.

### Step 4: Determine the Effect on pH
As the concentration of the weak acid increases and the concentration of the salt decreases, the ratio in the log term of the Henderson-Hasselbalch equation changes:
\[ \text{pH} = \text{pKa} + \log \left( \frac{[\text{Salt}]-y}{[\text{Acid}]+x} \right) \]

Since the denominator (weak acid concentration) is increasing and the numerator (salt concentration) is decreasing, the overall effect is that the log term decreases.

**Hint:** Remember that if the log term decreases, the pH must also decrease.

### Step 5: Conclusion
Thus, when `H2SO4` is added to an acidic buffer solution, the pH of the solution will decrease.

**Final Answer:** The pH will decrease.