Question

Find the molar solubility of BaCrO4 (Ksp= 2.1 × 10−10) in 3.5 × 10−3 M Na2CrO4

Answer 1

........BaCrO4 ==> Ba^2+ + CrO4^2-
I.......solid.......0.......0
C.......solid.......x.......x
E.......solid.......x.......x

Substitute the E line into Ksp expression and solve for x = solubility

Answer 2

This is a common ion problem. The C(initial) should have .0035M under CrO4^-2 which carries to E-line where 'x' can be dropped b/c it's too small to make a difference. The rest is perfect.