[jokerboy111]

Ok so heres the problem: 0.01M of Cu⁺ and 0.01M of Ag⁺ are in solution. A piece of solid NaI is put in inside. The question is what is the concentration of Ag⁺ as soon as the CuI begins to precipitate?

Here's what I know:

NaI--> Na⁺ + I^-
 so in solution,
Cu⁺ + I^- --> CuI   Ksp is 5.1 x 10^-12

Ag⁺ + I^- --> AgI   Ksp is 8.3 x 10^-17

so this means that AgI precipitates first.

If you set the Ksp for each of the reactions equal to the concentrations multiplied to solve for [Ag⁺],

in CuI, [I^-] = 5.1 x10^-10
in AgI, [I^-] = 8.3 x10^-15

So in order to find the concentration of Ag+ when CuI precipitates, do I do? :

       [Ag⁺]= Ksp of AgI/ [I^-] in CuI

       [Ag⁺]= 8.3 x10^-17/ 5.1 x 10^-10  = 1.627x 10^-7


so the concentration of Ag⁺ is 1.627 x10^-7 M??

[vhpk]

Of course, that's right