September's AP Problem

A 1.2516 gram sample of a mixture of CaCO₃ and Na₂SO₄ was analyzed by dissolving the sample and completely precipitating the Ca⁺² as (Calcium oxalate) CaC₂O₄.  The CaC₂O₄ was dissolved in sulfuric acid and the resulting H₂C₂O₄ was titrated with a standard KMnO₄ solution.

a)  Write the balanced equation for the titration reaction, shown unbalanced below.

MnO₄^-  +  H₂C₂O₄  +  H⁺  ---->    Mn⁺²  +  CO₂  +  H₂O

b)  The titration of the H₂C₂O₄ obtained required 35.62 milliliters of 0.1092 molar MnO₄^-    solution. Calculate the number of moles of H₂C₂O₄ that reacted with the MnO₄^-.

c)  Calculate the number of moles of CaCO₃ in the original sample.