Q17 of 30 Page 1

3 mL of ethanol is taken in a test tube and warmed gently in a water bath. A 5% solution of alkaline potassium permanganate is added first drop by drop to this solution, then in excess.

(i) How is 5 % solution of KMnO4, prepared?


(ii) State the role of alkaline potassium permanganate in this reaction. What happens on adding it in excess?


(iii) Write chemical equation of this reaction.


(i) The preparation of potassium permanganate can be done by taking 5g of KMnO4 In 100ml solution. This is weight/volume (strength) calculation.

(ii) Alkaline potassium permanganate is an oxidizing agent due to nascent oxygen which adds oxygen or removes hydrogen and thus oxidizes ethanol to ethanoic acid. Adding alkaline permanganate to ethanol, the pink colour of potassium permanganate vanishes, as it is being used up for the oxidation process.


(iii) Potassium permanganate react with ethanol as:


2KMnO4 + 3C2H5OH → 2MnO2 + 3CH3CHO + 2KOH + 2H2O


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