Solubility equilbrium

Question

5C2O4 + 2MnO4 + 16H → 2Mn + 10CO2 + 8H2O If 4 mL of 0.001 Μ KMnO4 solution is used to react completely with 250 mL of saturated CaC2O4 solution according to the above reaction, what will be the Ksp of CaC2O4 under the same conditions?

Answer 1

moles MnO₄^- = 4x10^-3 L x 1x10^-3 mole/L = 4x10^-6 moles MnO4^-

From mole ratio of C₂O₄^2- to MnO₄^- is 5:2, calculate moles of C₂O₄^2-

moles C₂O₄^2- = 4x10^-6 x 5/2 = 1x10^-5 moles C₂O₄^2-

[C₂O₄^2-] = 1x10^-5 moles/0.25 L = 4x10^-5 M

CaC₂O₄ ==> Ca²⁺ + C₂O₄^2- and [Ca²⁺] = [C₂O₄^2-]

Ksp = [Ca²⁺][C₂O₄^2-] = (4x10^-5)²

Ksp = 1.6x10^-9