Steve Marsden’s

In this simple experiment there are two reaction systems. Both share a common oxidizing agent: potassium permanganate, KMnO4. The purple MnO4- ion in acidic solution produces nearly colorless Mn2+ as it is reduced.

In one system this ion oxidizes colorless iron(II) to slightly yellow iron(III) ion. In the other, oxalate ion (C2O42-) is oxidized to carbon dioxide. The first part of the experiment is a comparison of the rates of these reactions. 10 drops of an acidic solution of Fe2+ is placed in a well and 10 drops of an acidic C2O42- solution is placed in another. Water is placed in a well between them to serve as a comparison for when the MnO4- is completely reacted.

It's fairly clear from the sample reaction that the iron(II) ion reacts much more quickly (instantaneously) than the oxalate ion. An investigation of the actual overall reaction in each case suggests a possible reason why.