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Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with iron Write the ionic equations for the reactions.

8.16 Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with

(i) iron

Write the ionic equations for the reactions.    

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M manish

Potassium permanganate can be prepared from the fusion of pyrolusite ore(MnO_{2}) with an alkali metal hydroxide and an oxidising agent (like KNO_{3}). This gives dark green K_{2}MnO_{4}. It disproportionates in acidic or neutral medium to give permanganate.

\\2MnO_{2}+4KOH+O_{2}\rightarrow 2K_{2}MnO_{4}+2H_{2}O\\ 3MnO_{4}^{2-}+4H^{+}\rightarrow 2MnO_{4}^{-}+MnO_{2}+H_{2}O

(i)Acidified permanganate ion reacts with iron-

\\MnO_{4}^{-}+8H^{+}+5e^{-}\rightarrow Mn^{2+}+4H_{2}O\\ Fe^{2+}\rightarrow Fe^{3+}+e^{-}]\times 5
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MnO_{4}^{-}+5Fe^{2+}+8H^{+}\rightarrow Mn^{2+}+ 5Fe^{3+}+4H_{2}O\\

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