The following equilibrium exists in aqueous solution : `CH_(3)COOH to H^(+) + CH_(3)COO^(-)`If dilute HCl is added :

Options

A. The equilibrium constant will increase
B. The equilibrium constant will decrease
C. Acetate ion concentration will increase
D. Acetate ion concentration will decrease

Explanation

To solve the problem regarding the equilibrium of acetic acid in aqueous solution when dilute HCl is added, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Equilibrium Reaction**:
The equilibrium reaction for acetic acid (CH₃COOH) in water can be represented as:
\[ \text{CH}_3\text{COOH} \rightleftharpoons \text{H}^+ + \text{CH}_3\text{COO}^- \]
Here, CH₃COOH is a weak acid that partially ionizes to produce hydrogen ions (H⁺) and acetate ions (CH₃COO⁻).

2. **Effect of Adding Dilute HCl**:
When dilute HCl is added to the solution, it dissociates completely in water:
\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \]
This increases the concentration of H⁺ ions in the solution.

3. **Application of Le Chatelier's Principle**:
According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust to counteract that change and restore a new equilibrium. In this case, the increase in H⁺ concentration will shift the equilibrium to the left:
\[ \text{CH}_3\text{COOH} \leftarrow \text{H}^+ + \text{CH}_3\text{COO}^- \]
This shift occurs because the system will try to reduce the concentration of H⁺ ions by favoring the formation of more CH₃COOH.

4. **Conclusion on Concentration Changes**:
As a result of the shift in equilibrium to the left, the concentration of acetate ions (CH₃COO⁻) will decrease. Therefore, the final conclusion is that the concentration of acetate ions decreases upon the addition of dilute HCl.

### Final Answer:
The concentration of acetate ions (CH₃COO⁻) will **decrease** when dilute HCl is added to the solution.

---