Take 2-3 ml ethanol in a test tube, add 5 ml sodium carbonate solution to it and warm the mixture by holding the test tube on the burner for a while. Do drop rise addition of a dilute solution of potassium permanganate to this warm mixture with stirring. Does the typical pink colour of potassium permanganate stay as it is in addition? Does the pink colour stop vanishing and stays on after some time of the addition process?

During this activity, ethanol gets oxidised by alkaline potassium permanganate to form ethanoic acid. Only certain bonds in the vicinity of the functional group take part in this reaction. When you add the pink coloured solution of potassium permanganate to ethanol, the pink colour disappears in the beginning, because potassium permanganate is used up in the oxidation reaction. At a certain point of the addition, oxidation of all the quantities of ethanol in the test tube is complete. If the addition of potassium permanganate continues beyond this point, it is not used up and becomes excess. The pink colour of this excess potassium permanganate does not vanish, but stays as it is.

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