Question

what is the solubility of barium sulfate in a solution containing 0.050 M sodium selfate? The Ksp value for barium sulfate is 1.1E-10.



An insoluble salt with formula MX3 has a solubility product constant written in terms of solubility,s, in the form
a) Ksp=s2
b)Ksp=4s3
c) Ksp=27s4
d)Ksp=256s5

Answer 1

A) Solubility of BaSO4 is worked similar to the CaCO3 problem. The principle difference is that the solution has Na2SO4 in it. Note Na2SO4 is a common ion (the sulfate ion is the common ion). What does that do. Sulfate comes from two sources; i.e., from BaSO4 (where it will be x) and from Na2SO4 (where it will be 0.05M). So the BaSO4 problem will be
Ksp = (Ba^2+)(SO4^2-)
Ksp = (x)(x+0.05) and solve for x.

B)I assume X is a halogen which then means M must be +3 element.
MX3(s) ==> M^3+ + 3X^-
Ksp = (M^3+)(X^-)^3
So set up the ICE chart in terms of s (follow the examples before where we let solubility be x) and plug that into Ksp expression. The correct answer is listed in the choices.