A saturated solution of calcium chromate (CaCrO4) freezes at -0.10 C. What is Ksp for CaCrO4? Assume complete dissociation. The density of the solution is 1.0 g/mL.

Answer 1

I would do this.
delta T = i*Kf*m
0.10 = 2*1.86*m
Solve m = 0.02688
m = mols/kg solvent and for such dilute solution and a density of 1.0 g/mL that is essentially 1L solution or molarity.

So Ksp = (Ca^2+)(CrO4^2-)
Ksp = (0.02688)^2
I don't have that Ksp value in any of my texts but this site is in the same park as this answer of 7.2E-4
http://users.stlcc.edu/gkrishnan/ksptable.html

Answer 2

Thanks so much! I never would've figured that out.