[killazerg]

Calculate the concentration of I- in a solution obtained by shaking 0.20M KI with an excess of AgCl(s)

I uploaded the question to imgur:

http://i.imgur.com/DVZYn.png

I try to solve this as a K = Kf x Ksp problem, but I run into issues when looking for values of Kf since I can't find any for AgI. I'm looking for a conceptual plan to solve this

Here is where I m as of now and maybe someone can point out the mistake

AgCl(s)  Ag⁺¹ + Cl^-1
Ksp = 1.77 x 10^-10

Ag⁺¹ + I^-1  AgI
Kf = ?

AgCl (s) + I^-1  AgI + Cl^-1
K = Ksp x Kf

K = [AgI][Cl^-1]/[I^-1]


I^-1  AgI + Cl^-1
0.20             0       0
-S               +S     +S
0.20-S          S       S

K = S²/(0.2-S)

So I am stuck here because I cannot find Kf for AgI. What am I doing wrong?

Thank you!

[Hunter2]

K(AgI) = 1 *10^-10 (mol/l)²

Calculate the amount of silver in saturated AgCl. With this value you can calculate the AgI.

[Borek]

Why are you looking for Kf (whatever it is), instead of Ksp for AgI?

[killazerg]

Kf is the complex ion formation constant in water at 25^oC

I think I may have set up this problem incorrectly. The appendix provides all values of Ksp and Kf so that I can find K. Because the one I am looking for is not there, it may be due to improperly setting up this problem

[Big-Daddy]

Why use a Kf anyway? You can use the reverse of the Ksp of AgI instead:

AgI (s) -> Ag⁺ (aq) + I^- (aq)

Which is the Ksp of AgI; take 1/this value to find the opposite direction's constant, which is what you want. Then what ... solve the rest, let me know how you get along.