The addition of NaCl to AgCI decreases the solubility of AgCl, because

Options

A. `K_(sp)` of AgCl decreases
B. `K_(sp) ` of AgCI increases
C. Solution becomes supersaturated
D. Ionic product exceeds the `K_(sp)` value

Answer

To solve the question regarding the effect of adding NaCl on the solubility of AgCl, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Solubility**:
- Solubility refers to the maximum amount of a solute that can dissolve in a solvent at a given temperature. For AgCl, its solubility in water is limited.

2. **Dissociation of AgCl**:
- When AgCl is added to water, it dissociates into its ions:
\[ \text{AgCl (s)} \rightleftharpoons \text{Ag}^+ (aq) + \text{Cl}^- (aq) \]

3. **Adding NaCl**:
- Sodium chloride (NaCl) is a highly soluble salt that dissociates completely in water:
\[ \text{NaCl (s)} \rightleftharpoons \text{Na}^+ (aq) + \text{Cl}^- (aq) \]
- Therefore, when NaCl is added to the solution, it increases the concentration of Cl⁻ ions in the solution.

4. **Common Ion Effect**:
- The increase in the concentration of Cl⁻ ions due to the addition of NaCl leads to a phenomenon known as the "common ion effect."
- According to Le Chatelier's principle, if a system at equilibrium is disturbed by changing the concentration of one of the components, the equilibrium will shift to counteract that change.

5. **Shift in Equilibrium**:
- In this case, the increase in Cl⁻ concentration shifts the equilibrium of the dissociation of AgCl to the left:
\[ \text{Ag}^+ (aq) + \text{Cl}^- (aq) \leftarrow \text{AgCl (s)} \]
- This shift results in the formation of more solid AgCl, thereby decreasing the amount of AgCl that can remain dissolved in the solution.

6. **Conclusion**:
- Therefore, the addition of NaCl decreases the solubility of AgCl due to the common ion effect, where the increased concentration of Cl⁻ ions suppresses the dissociation of AgCl.

### Final Answer:
The addition of NaCl to AgCl decreases the solubility of AgCl because of the common ion effect, where the increased concentration of Cl⁻ ions shifts the equilibrium to favor the formation of solid AgCl.

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