Answer to Question #301930 in General Chemistry for Paul Hackman

Question

5.Balance the equation below and use it to answer the questions that follow:

C₂O₄^2-(aq) + MnO₄^-(aq) + H⁺(aq) = CO₂(g) + Mn²⁺(aq) + H₂O(I)

(I) Which ionic species is an oxidizing agent and which is a reducing agent

(II) Twenty five 25 cm³ of a solution of sodium ethanediote of concentration 0.1 mol dm^-3 were placed in a conical flask. A burrete was filled with patassium manganate (VII) solution of concentration 0.038 mol dm^-3 . Determine the volume of the manganate (VII) solution that would be needed to give the endpoint in the titration.

(III) Assuming that the KMnO₄ was prepared by dissolving 6.94 g of salt in 1 dm³ of solution. Calculate the % purity of KMnO₄

Answer 1

C₂O₄^2-(aq) + MnO₄^-(aq) + 8H⁺(aq) = 2CO₂(g) + Mn²⁺(aq) + 4H₂O(I)

(I) 2Mn^VII + 10 e^- → 2Mn^II (reduction).

10C^III - 10 e^- → 10C^IV (oxidation).

MnO^4- is an oxidizing agent,

C₂O₄^2- is a reducing agent.

(II) C₁V₁ = C₂V₂

25 cm³ x 0.1 mol/dm³ = 0.030 mol/dm³ x V

V = 25 cm³ x 0.1 mol/dm³ / 0.030 mol/dm³ = 83.3 cm³

(III) n (KMnO₄) = 6.94 g / 158 g/mol = 0.044 mol

% purity = 0.038 / 0.044 x 100% = 86.4%