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Indicate the steps in the preparation of:  KMnO4 from pyrolusite ore. - Chemistry

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ConceptSome Important Compounds of Transition Elements - Oxides and Oxoanions of Metals

Question

Indicate the steps in the preparation of:  KMnO4 from pyrolusite ore.

 

Solution

Potassium permanganate (`KMnO_4`) can be prepared 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 give K2MnO4.

The green mass can be extracted with water and then oxidized either electrolytically or by passing chlorine/ozone into the solution.

Electrolytic oxidation

`K_2MnO_4 harr 2K^(+) + MnO_4^(2-)`

`H_2O harr H^(+) + OH^(-)`

At anode, manganate ions are oxidized to permanganate ions.

`MnO_4^(2-) harr MnO_4^(-) + e^(-)`

Green           Purple

Oxidation by chlorine

`2K_2MnO_4 + Cl_2 -> 2KMnO_4 + 2KCl`

`2MnO_4^(2-) + Cl_2 -> 2MnO_4^(-) + 2Cl^(-)`

Oxidation by ozone

`2K_2MnO_4 + O_3 + H_2O -> 2KMnO_4 + 2KOH + O_2`

`2MnO_4^(2-) + O_3 + H_2O -> 2MnO_4^(2-) + 2OH^(-) +O_2`

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APPEARS IN

 NCERT Solution for Chemistry Textbook for Class 12 (2018 to Current)
Chapter 8: The d-block and f-block Elements
Q: 26.2 | Page no. 235
Solution Indicate the steps in the preparation of:  KMnO4 from pyrolusite ore. Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals.
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