Redox Chemistry

Question

What is the molarity (mol/L) of a potassium permanganate solution if 12.02 mL of it was used to titrate a 10.84 mL sample of a 0.1826 M sodium oxalate standard solution.

Answer 1

The balanced equation for the titration of oxalate with permanganate is as follows:

2MnO₄^- + 5C₂O₄^2- + 16H⁺ ==> 10CO₂ + 2Mn²⁺ + 8H₂O

(note: if you don't know how to balance redox reactions in acid, submit a separate question on that topic)

From the balanced equation, we see that it takes 2 moles MnO₄^- to react with 5 moles C₂O₄^2-. Thus, using these factors, we can find the moles and molarity of the permanganate (MnO₄^-).

moles C₂O₄^2- present = 10.84 ml Na₂C₂O₄ x 1 L/1000 ml x 0.1826 mol/L x 1 mol C₂O₄^2-/mol Na₂C₂O₄ = 0.001979 moles C₂O₄^2- present

moles MnO₄^- used = 0.001979 mols C₂O₄^2- x 2 mols MnO₄^-/5 mols C₂O₄^2- = 0.0007918 moles used

Molarity of MnO₄^- solution = 0.0007918 moles/0.01212 L = 0.06533 M