Redox Titration: Potassium Permanganate and Sodium Oxalate

REDOX TITRATION: Potassium Permanganate
and Sodium Oxalate
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
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+
To quantitatively determine the concentration of a standard KMnO4 solution by
titration with a known mass of sodium oxalate.
50 mL buret
KMnO4 solution
Na2C2O4 crystals
1 M sulfuric acid
hot plate/stirrer
stir bar
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 80C to 90C.
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
REDOX TITRATION: Potassium Permanganate
and Sodium Oxalate
Data Table
Data Table:
Mass of sodium oxalate
Volume of potassium
permanganate required
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.
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