Question

A solution of 0.2 g of a compound containing Cu²⁺ and C₂O^2-₄ ions on titration with 0.02 M KMnO₄ in presence of H₂SO₄ consumes 22.6 mL of the oxidant. The resultant solution is neutralized with Na₂CO₃, acidified with dilute acetic acid and treated with excess KL The liberated iodine requires 11.3 mL of 0.5 M Na₂S₂O₃ solution for complete reduction. Find out the mole ratio of Cu⁺ to C₂O₄^2- in the compound. Write down the balanced redox reactions involved in the above titrations.

Answer 1

Let a moles of Cu²⁺ and b moles of C₂O^2-₄ be present in solution.

(i) The solution is oxidised by KMnO₄ which reacts with only C₂O^2-₄

(ii) After oxidation of C₂O^2-₄ , the resulting solution is neutralized by Na₂CO₃, acidified with dilute CH₃COOH and then treated with excess of KI. The liberated I₂, required Na₂S₂O₃ for its neutralisation,