Calcium levels in blood can be determined by adding oxalate ion to precipitate calcium oxalate, CaC2O4, followed by dissolving the precipitate in aqueous acid and titrating the resulting oxalic acid (H2C2O4) with KMnO4:
5 H2C2O4 (aq) + 2MnO4- (aq) + 6 H+ (aq) ----> 10 CO2 (g) + 2Mn2+ (aq) + 8 H2O (l)
How many milligrams of Ca2+ are present in 10.0 mL of blood if 21.08 mL of 0.000988 M KMnO4 solution is needed for the titration?