Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: killazerg on November 10, 2012, 11:28:37 PM
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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) ::equil:: Ag+1 + Cl-1
Ksp = 1.77 x 10-10
Ag+1 + I-1 ::equil:: AgI
Kf = ?
AgCl (s) + I-1 ::equil:: AgI + Cl-1
K = Ksp x Kf
K = [AgI][Cl-1]/[I-1]
I-1 ::equil:: 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!
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K(AgI) = 1 *10-10 (mol/l)2
Calculate the amount of silver in saturated AgCl. With this value you can calculate the AgI.
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Why are you looking for Kf (whatever it is), instead of Ksp for AgI?
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Kf is the complex ion formation constant in water at 25oC
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
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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.