Apparatus: Test tube, Bunsen burner, measuring cylinder, dropper, etc.
Chemicals : Ethanol,sodium carbonate, dilute solution to it and warm the mixture by holding the test tube on the burner for a while. Do drop wise addition of a dilute solution of potassium permanganate to this warm mixutre with stirring.
Does the typical pink colour of potassium permanganate stay as it is on addition? Does the pink colour stop vanishing and stays on after some time of the addition process?

Explanation

i. When potassium permanganate is added dropwise to warm mixture of ethanol and sodium carbonate with constant stirring, the pink colour of potassium permanganate disappears as it oxidizes ethanol present in the mixture.
ii. Once all the quantity of ethanol is oxidized and if further addition of potassium permanganate is continued, then this excess potassium permanganate will not be decolourized.
Hence, the pink colour stops vanishing and stays on indicating the completion of oxidation reaction.