12.(10) Calcium and magnesium ions can be separated from one another from a solution that contains both ions by sequential precipitation of the oxalate salts, CaC2O4 and MgC2O4. Ksp for calcium oxalate is 2.3 x 10-9 and Ksp for magnesium oxalate is 8.6 x 10-5. If you have a solution that is 0.020 M in Ca+2 and in Mg+2, and you start adding ammonium oxalate, (NH4)2C2O4, to this solution:
a. Which metal oxalate precipitates first?
b. What is the concentration of the first metal ion to precipitate when the second metal oxalate begins to precipitate?