Question

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.

Answer 1

i) Preparation of $5\%$ Potassium permanganate : $5\%$solution of${\mathrm{KMnO}}_4$ is prepared by dissolving 5 grams of ${\mathrm{KMnO}}_4$in $100ml$ of water.

ii) Role of alkaline potassium permanganate

• Alkaline potassium permanganate is adding oxygen to alcohol and converts it to acid.
• Hence, it acts as an oxidizing agent.
• When ${\mathrm{KMnO}}_4$ is added, initially color disappears because colored permanganate ions of potassium permanganate are consumed to oxidize ethanol.
• When an excess of ${\mathrm{KMnO}}_4$ is added, color does not change because there is no more alcohol left for the reaction.

iii) Chemical equation of the above reaction : the reaction is given below ,

$\underset{\mathrm{Ethanol}}{{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}}\stackrel{\mathrm{alk}{\mathrm{KMnO}}_4+\mathrm{heat}}{\to }\underset{\mathrm{Ethanoic}\mathrm{acid}}{{\mathrm{CH}}_3\mathrm{COOH}}$