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 dischromate and write the ionic equations for its reaction with (i) an iodide (ii) `H_(2)S`.

Explanation

Preparatin of potassium permanganate :
(i) It is prepared from mineral, pyrolusite `(MnO)_(2)`
(ii) `MnO_(2)` is fussed with KOH in presence of air or oxidising agent as `KNO_(3)` when green coloured potassium manganate is formed.
`2MnO_(2)+4KHO+O_(2)to underset("Manganate")underset("Potassium")(2K_(2)MnO_(4))+2H_(2)O`
`or 2MnO_(2)+2KOH+KNO_(3)toK_(2)MnO_(4)+KNO_(2)+H_(2)O`
(iii) Oxidation fo potassium manganate is carried out by bubbling `CO_(2),` chlorine to get potassium permanganate.
`3K_(2)MnO_(4)+2CO_(2)to2KMnO_(4)+MnO_(2) darr2K_(2)CO_(3)`
`or 2MnO_(2)+2KOH+KNO_(3)toK_(2)MnO_(4)+2HCl`
Reaction f acidified `KMnO_(4)` with oxalic acid :
`2KMnO_(4)+3H_(2)SO_(4)+5C_(2)H_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+8H_(2)O+10CO_(2)`