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Discuss chemical properties of potassium permanganate |
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Answer» Solution :Decomposition of POTASSIUM permanganate at 513K gives GREEN coloured potassium manganate. `2KMnO_(4) rarr K_(2)MnO_(4) + MnO_(2) + O_(2)` Acidified permanganate solution is a good oxidizing agent. It oxidizes Fe(II) to Fe(III), `NO_(2)^(-) " to " NO_(30^(-)` and iodides to iodine. The half reactions of the reductants are: (i) `underset(underset(COO^(-))(5|))(C )OO^(-) rarr 10CO_(2) + 10e^(-)` (ii) `5Fe^(2+) rarr 5Fe^(3+) + 5e^(-)` (iii) `5NO_(2)^(-) + 5H_(2)O rarr 5NO_(3)^(-) + 10H^(+) + 10e^(-)` (iv) `10I^(-) rarr 5I_(2) + 10e^(-)` In acidic medium, the hydronium ion concentration plays an important role in kinetics of the REDOX reaction `MnO_(4)^(-) + e^(-) rarr MnO_(4)^(2-) {E^(@)= +0.56V]` `MnO_(4)^(-) + 4H^(+) + 3e^(-) rarr MnO_(2) + 2H_(2)O {E^(@) = +1.69V]` `MnO_(4)^(-) + 8H^(+) + 5e^(-) rarr Mn^(2+) + 4H_(2)O [E^(@) = +1.52V]` Permanganate at `[H^(+)] =1`, should oxidize water but in practise the reaction is extremely slow UNLESS temperature is raised OR Mn(II)ions are present |
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