REDOX TITRATION: Potassium Permanganate and Sodium Oxalate Introduction: The permanganate ion, KMnO4, is a very strong oxidizing agent. The half-reaction is: E = MnO4 + 8H+ Mn2+ + 4H2O E = 1.51 V The half-reaction for permanganate only occurs in solutions that are 0.1M or greater in strong acid. In less acidic media, the product may be Mn(III), Mn(IV), or Mn(VI), depending on conditions. The permanganate ion is very useful in a redox titration. Because of its intense purple color, no other indicator is necessary. A persistent pink color indicates that the reaction is complete. However, the permanganate endpoint is not permanent because excess permanganate ions react with the relatively large number of Mn(II) ions present at the end point. 2MnO4 + 3 Mn2+ + 2H2O 5MnO2(s) + 4H+ Purpose: To quantitatively determine the concentration of a standard KMnO4 solution by titration with a known mass of sodium oxalate. Materials/Equipment: 50 mL buret KMnO4 solution Na2C2O4 crystals 1 M sulfuric acid hot plate/stirrer stir bar balance thermometer Procedure: 1. Weigh out a 0.10 to 0.15 g sample of dry sodium oxalate. The Na2C2O4 should be dried in an oven for about an hour and cooled in a desiccator. 2. Dissolve the Na2C2O4 in about 250 mL of 1 M H2SO4 in a 400 mL beaker. 3. Begin heating the solution until it reaches a temperature of 80C to 90C. 4. Fill a 50 mL buret with the standard permanganate solution while the sodium oxalate solution in the beaker is heating. 5. Once the correct temperature has been reached, begin adding the permanganate slowly from the buret. Wash down any permanganate that spatters on the wall of the beaker. Take the first consistent pink color ( 30 seconds) as the end point. Record the final buret reading. 6. Immediately empty the buret into a waste container. Partial decomposition to MnO4 may occur. REDOX TITRATION: Potassium Permanganate and Sodium Oxalate Data Table Name: Date: Period/Group: Data Table: Mass of sodium oxalate Volume of potassium permanganate required g mL Write a balanced redox equation for the reaction of potassium permanganate and sodium oxalate. MnO4 + C2O42- Mn2+ + CO2 Calculate the molar concentration of the potassium permanganate solution.