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, we will analyze the given equilibrium and the effect of adding dilute HCl on it.

### Step-by-Step Solution:

1. **Identify the Equilibrium Reaction:**
The equilibrium reaction is:
\[ \text{CH}_3\text{COOH} \rightleftharpoons \text{H}^+ + \text{CH}_3\text{COO}^- \]
Here, CH₃COOH is acetic acid, which is a weak acid that partially dissociates in water 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 to give more H⁺ ions:
\[ \text{HCl} \rightarrow \text{H}^+ + \text{Cl}^- \]
This increases the concentration of H⁺ ions in the solution.

3. **Applying Le Chatelier's Principle:**
According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in concentration, pressure, or temperature, the system will adjust to counteract the change and restore a new equilibrium.
- In this case, the increase in H⁺ concentration will shift the equilibrium to the left (backward direction) to reduce the concentration of H⁺ ions.

4. **Resulting Changes in Concentration:**
- As the equilibrium shifts to the left, the concentration of acetate ions (CH₃COO⁻) will decrease because more acetate ions will combine with H⁺ ions to form acetic acid (CH₃COOH).

5. **Conclusion:**
Therefore, the correct conclusion is that the concentration of acetate ions (CH₃COO⁻) will decrease upon the addition of dilute HCl.

### Answer:
The concentration of acetate ions (CH₃COO⁻) will decrease.

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