Thu February 17, 2011 By: Anupama Ray

why the colour of potassium permaganate not disappear when it is added in excess in a warm solution of ethanol?

Expert Reply
Fri February 18, 2011
Dear Student
KMnO4 is pink in a solution without oxidizing reagents. Adding ethanol should change it to a brown solution. If adding ethanol can not change the solution to brown, then its environment is already acidic and will not reduce.

When potassium permanganate reacts with ethanol, it releases nascent oxygen. ie, an atom of oxygen thus converting the ethanol to acetic acid. Initially colour disappears because coloured permanganate ions of potassium permanganate are consumed to oxidise ethanol.


When excess is added colour does not change because there is no more alcohol left and hence there is no reaction.
We hope that clarifies your query.
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