Consider the solution of the previous problem containing three metal cations;

[Pb²⁺] = [Ag⁺] = [Hg₂²⁺ ] = 0.0015M.

We just determined that:

The PbCl₂ system was at equilibrium when [Cl^–] = 0.11 M,

The AgCl system was at equilibrium when [Cl^–] = 1.2 X 10^–7 M,

The Hg₂Cl₂ system was at equilibrium when [Cl^–] = 3.1 X 10^–8M.

Questions:
What concentration of Cl^– ions is needed to precipitate all of the ions but Pb²⁺?

What is the concentration of Hg₂²⁺ ions in the solution at this concentration of Cl^–?