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How Oxidation by potassium Manganate (VII) (KMnO4) take place

Answer Text:
Oxidation by potassium Manganate (VII) (#KMnO_4#)
Procedure:
- Purple Potassium manganate (VII) is added into a solution containing iron (II) ions in a test tube.
- A few drops of concentrated sulphuric (VI) acid are added.
Observations:
- The purple solution (containing Manganate (VII) ions) turns to colourless (manganate (II) ions) i.e. the purple solution is decolourised;
Explanation:
- The Manganate (VII) ions which give the solution a purple colour are reduced to Manganese (II) ions which appear colourless.
This is a redox reaction.

Note:
-oxidation number of Manganate ions in# KMnO_4# decreases from 7 to 2 (in #Mn^(2+)#) hence reduction; while oxidation number of iron increases from 2 (in #Fe^(2+)#) to 3 (in #Fe^(3+)#); hence oxidation;
-The presence of #Fe^(3+)# at the end of the reaction can be detected by adding sodium hydroxide solution to form a red brown precipitate of# Fe(OH)_3#;