1. Special Cases for Ksp

2. Comparing Solubilities from Ksp values
Easy ones – contains same number of dissolved particles
AgI (s)  Ag + (aq) + I – (aq) Ksp = 1.5 x
CaSO4 (s)  Ca 2+(aq) + SO4 2-(aq) Ksp = 6.1 x 10 -5
Which one is more soluble?
Largest value is the most soluble

3. Not the same number of dissolved particles.
PbF2 (s) 
(X)(2X)2 = 4 x 10 -8
SrSO4 (s) 
(X)(X) = 3.2 x 10 -7
Solubilities from above calculations.
PbF2 (s) = M
SrSO4 (s) = M
Pb2+(aq) + 2 F-(aq) Ksp = 4 x 10-8
Sr2+ (aq) + SO4 2–(aq) Ksp = 3.2 x 10-7
PbF2 is more soluble even though it has a smaller Ksp value

4. Common Ion Effect Ag2CrO4 solution mixed with 0.10 M AgNO3
Calculate the solubility of this solution
Ag2CrO4 (s)  2 Ag +(aq) + CrO4 2-(aq) Ksp = 9.0 x
I ? M
C X X
E X X
Ksp = [Ag+]2[CrO42-]
Assume X = 0 and solve
X = 9.0 x M
Just Ag2CrO4 = x M
= ( X)2(X) = 9.0 x

5. Will a Precipitate form?
Find Q, which is found the same as Ksp. Compare Q to Ksp , if Q > Ksp, then ppt forms Mix M Ce 3+ with M IO3 – Write dissociation of would be solid. Ce(IO3)3 (s)  Ce 3+(aq) + 3 IO3 – (aq) Q = [Ce 3+][IO3 -]3 Ksp = 1.9 x Q > Ksp so solid forms
= [ ][ ]3 = 5.32 x