What is the solubility of AgCl in a solution of 7.53 x 10-2 M MgCl2?

Question

The Ksp of AgCl is 1.63 x 10-10.

Answer 1

Elva,

This should be recognized as a problem dealing with the "common ion effect". In the case, the common ion is Cl^- since it is common to both AgCl and MgCl₂.

AgCl(s) <==> Ag⁺(aq) + Cl^-(aq)

Ksp = [Ag⁺][Cl^-]

1.63x10^-10 = [Ag⁺][Cl^-] and since the Cl^- concentration can be taken as that contributed from the MgCl₂ ...

7.53x10^-2 M MgCl₂ ==> 7.53x10^-2 M Mg²⁺ + (2)(7.53x10^-2 M) Cl^- = 0.1506 M Cl^-

1.63x10^-10 = [Ag⁺][0.1506]

[Ag⁺] = 1.08x10^-9 M = solubility of AgCl in 7.53x10^-2 M MgCl₂