Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with oxalic acid? Write the ionic equation for the reaction.
OR
Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with (i) an iodide (ii) `H_(2)S`.

Explanation

It is prepared by rfusion nof pyrolusite, `MnO_(2)`, with KOH in the presence of an oxidising agent like `KNO_(3)`. This produces the dark green potassium mangnate.
`KMnO_(4)` which disproportionates neutral in a or acidic solution to give purple permagnate. ltBrgt (i) `MnO_(2)+2KOH+KNO_(3)toK_(2)MNO_(4)+KNO_(2)+H_(2)O`
(ii) `3MnO_(4)^(2-)+4H^(4)to2MnO_(4)^(-)+MnO_(2)+2H_(2)O`
(iii) `2MnO_(4)^(-)+16H^(+)+5C_(2)O_(4)^(2-)to2Mn^(2+)+8H_(2)O+10CO_(2)`
OR
(i) `Cr_(2)O_(7)^(2-)+14H^(+)+6I^(-)to2Cr^(3+)+7H_(2)O+3I_(2)`
(ii) `Cr_(2)O_(7)^(2-)+8H^(+)+3H_(2)Sto2Cr^(3+)+7H_(2)O+3S`