To a buffer solution of `CH_(3),COOH` and `CH_(3),COONa`, some HCI is added. Then the reaction involved is

Options

A. `CH_(3)COOH+OH^(-) rarr CH_(3)COO^(-)+H_(2)O`
B. `CH_(3)COO^(-)+H^(+)rarr CH_(3)COOH`
C. `Na^(+)OH^(-) rarr NaOH`
D. `CH_(3)COO^(-)+Na^(+) rarr CH_(3)COONa`

Answer

To solve the problem regarding the reaction involved when HCl is added to a buffer solution of acetic acid (CH₃COOH) and sodium acetate (CH₃COONa), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components of the Buffer Solution**:
- The buffer solution consists of acetic acid (CH₃COOH), which is a weak acid, and sodium acetate (CH₃COONa), which provides the acetate ion (CH₃COO⁻) in solution.

2. **Understand the Nature of the Buffer**:
- Acetic acid (CH₃COOH) can dissociate in water to form acetate ions (CH₃COO⁻) and hydrogen ions (H⁺):
\[ \text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+ \]

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

4. **Reaction with Acetate Ions**:
- The added H⁺ ions will react with the acetate ions (CH₃COO⁻) present in the buffer. According to Le Chatelier's principle, the equilibrium will shift to the left to counteract the increase in H⁺ concentration:
\[ \text{CH}_3\text{COO}^- + \text{H}^+ \rightarrow \text{CH}_3\text{COOH} \]

5. **Final Reaction**:
- The overall reaction when HCl is added to the buffer solution can be summarized as:
\[ \text{CH}_3\text{COO}^- + \text{H}^+ \rightarrow \text{CH}_3\text{COOH} \]

### Conclusion:
The reaction involved when HCl is added to the buffer solution of acetic acid and sodium acetate is:
\[ \text{CH}_3\text{COO}^- + \text{H}^+ \rightarrow \text{CH}_3\text{COOH} \]