Which of the following compounds will have the highest molar solubility in pure water ?
a. FeS, Ksp = 3.72 x 10 -19
b. PbS, Ksp = 9.04 x 10 -29
c. MgCO3, Ksp = 6.82 x 10 -6
d. PbSO4, Ksp = 1.82 x 10 -8
e. AgI, Ksp = 8.51 x 10 -17
We’re being asked to determine which compound has the highest molar solubility in pure water.
Recall that Ksp is an equilibrium constant related to slightly soluble ionic compounds.
The dissociation of slightly soluble ionic compounds in solution is as follows:
MnNm(s) ⇌ n Mm+(aq) + m Nn–(aq)
We can construct an ICE table for this dissociation.
Remember that solids are ignored in the ICE table and Ksp expression.