Answer:
The solubility of AgCl in water decreases.
Step-by-step explanation:
When we add AgNO₃ we are adding silver ions. Therefore, in addition to the dissociation of AgCl, the following process also contributes to the total concentration of the common silver ions in solution:
AgNO₃ (s) → Ag⁺ (aq) + NO₃⁻ (aq)
The solubility equilibrium of AgCl is:
AgCl(s) ⇄ Ag⁺ (aq) + Cl⁻ (aq)
If AgNO₃ is added to a saturated AgCl solution, the increase in [Ag⁺] will make the ion product greater than the solubility product:
Q = [Ag⁺]₀[ Cl⁻]₀ > Ksp
To reestablish equilibrium, some AgCl will precipitate out of the solution, as Le Châtelier’s principle would predict, until the ion product is once again equal to Ksp.
The effect of adding a common ion, then, is a decrease in the solubility of the salt (AgCl) in solution. Note that in this case [Ag⁺] is no longer equal to [Cl⁻] at equilibrium.