When small amount of an acid or alkali is mixed with a buffer solution, then pH of buffer solution

Options

A. does not changes
B. Changes slightly
C. Increases
D. Decreases

Answer

**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. It typically consists of a weak acid and its conjugate base (for acidic buffers) or a weak base and its conjugate acid (for basic buffers).

2. **Effect of Adding Acid or Base:**
- When a small amount of acid (H⁺ ions) is added to an acidic buffer, the weak acid (HA) in the buffer will react with the added H⁺ ions to form more of its conjugate base (A⁻). This minimizes the increase in H⁺ concentration, thus limiting the decrease in pH.
- Conversely, when a small amount of base (OH⁻ ions) is added, the weak acid (HA) will donate a proton (H⁺) to the hydroxide ions to form water (H₂O) and its conjugate base (A⁻). This neutralizes the effect of the added base, preventing a significant increase in pH.

3. **Magnitude of pH Change:**
- The buffer's capacity to resist pH changes is effective only for small amounts of added acid or base. If the amount added is small, the pH will change slightly but not significantly.
- If a large amount of acid or base is added, the buffer may not be able to maintain the pH, leading to a more considerable change in pH.

4. **Conclusion:**
- Therefore, when small amounts of acid or alkali are mixed with a buffer solution, the pH of the buffer solution will change slightly, but it will not vary significantly.

**Final Answer:**
When small amounts of an acid or alkali are mixed with a buffer solution, the pH of the buffer solution changes slightly.

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