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Home » Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron(II) ions (ii) SO2 and (iii) oxalic acid?
Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron(II) ions (ii) SO2 and (iii) oxalic acid?
CBSE | Chemistry | Class 12 | NCERT | The d & f Block Elements
Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron(II) ions (ii) SO2 and (iii) oxalic acid?

Write the ionic equations for the reactions.

The preparation of potassium permanganate can be done from pyrolusite (MnO2). The ore is fused with KOH in the presence of either atmospheric oxygen or an oxidising agent, such as KNO3 or KClO4, to yield K2MnO4.

The green mass can be extracted with the help of water and then oxidized either electrolytically or by passing chlorine/ozone into the solution. Electrolytic oxidation can be shown as:

    \[4{K_{2}}Mn{O_4} \leftrightarrow 2{K^ + } + MnO_4^{2 - }\]

    \[{H_{2}}O \leftrightarrow {H^ + } + O{H^ - }\]

At anode, manganate ions are oxidized to permanganate ions.

    \[MnO_4^{2 - } \leftrightarrow MnO_4^ - + {e^ - }\]

Oxidation with the help of chlorine:

    \[{K_{2}}Mn{O_{4}} + C{l_{2}} \to 2Mn{O_{4}} + 2KCl\;\]

    \[2MnO_4^{2 - } + C{l_2} \to 2MnO_4^{2 - } + 2C{l^ - }\]

Oxidation with the help of ozone:

​

    \[2KMn{O_4} + {O_3} + {H_2}O \to 2KMn{O_4} + 2KOH + {O_2}\]

 

    \[2MnO_4^{2 - } + {O_{3}} + {H_{2}}O \to 2MnO_4^{2 - } + 2O{H^ - } + {O_2}\]

​

(i) Acidified KMnO4 solution oxidizes Fe (II) ions to Fe (III) ions i.e., Fe2+ to Fe+3 ions.

Acidified potassium permanganate oxidizes SO2 to sulphuric acid.

Acidified potassium permanganate oxidizes oxalic acid to carbon dioxide.

i

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