A basic buffer solution contains a weak base BOH and its conjugate acid `BH^(+)`. On adding some HCI. which of the following reactions takes place to maintain constant pH ?

Options

A. `BH^(+) rarr B+H^(+)`
B. `B+H_(2)O rarr BH^(+) +OH^(-)`
C. `H^(+)+OH^(-)rarrH_(2)O`
D. `BH^(+)+OH^(-)rarr B+H_(2)O`

Answer

To solve the problem regarding the basic buffer solution containing a weak base (BOH) and its conjugate acid (BH⁺) when HCl is added, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of the Buffer**:
- A basic buffer solution consists of a weak base (BOH) and its conjugate acid (BH⁺).
- When BOH is dissolved in water, it partially ionizes to produce B⁺ and OH⁻ ions:
\[ \text{BOH} \rightleftharpoons \text{B}^+ + \text{OH}^- \]

2. **Adding HCl to the Buffer**:
- When HCl, a strong acid, is added to the buffer solution, it dissociates completely to release H⁺ ions:
\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \]

3. **Reaction to Maintain pH**:
- The increase in H⁺ ions from HCl will disturb the pH of the solution. To counteract this, the H⁺ ions will react with the hydroxide ions (OH⁻) present in the buffer:
\[ \text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O} \]
- This reaction reduces the concentration of OH⁻ ions, thus minimizing the change in pH.

4. **Role of the Conjugate Acid**:
- The presence of the conjugate acid (BH⁺) helps to maintain the buffer capacity. The reaction between H⁺ and OH⁻ produces water, which helps to keep the concentrations of H⁺ and OH⁻ balanced, thereby maintaining the pH of the solution.

5. **Conclusion**:
- The overall reaction that takes place to maintain a constant pH in the buffer solution upon the addition of HCl is:
\[ \text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O} \]
- This reaction ensures that the pH remains relatively constant despite the addition of the strong acid.