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Postassium permanganate is manufactured ...

Postassium permanganate is manufactured a large scale by fusing - with KOH and `KNO_(3)` to form `K_(2)MnO_(4)`, which is than electrolytically oxidized in an alkaline medium.

A

manganite, `Mn_(2)O_(3)` . `H_(2)O`

B

hausmannite, `Mn_(3)O_(4)`

C

pyrolusite, `MnO_(2)`

D

braunite, `Mn_(2)O_(3)`

Text Solution

Verified by Experts

The correct Answer is:
C
`MnO_(2)` `overset ("fuse with KOH") underset ("oxidize with" KNO_(3)) rarr` `MnO_(4)^(2-)` `overset ("electrolytic oxidation") underset ("in alkaline solution") rarr` `MnO_(4)^(-)`
The function of `KNO_(3)` is to provide `O_(2)` to oxidize `MnO_(2)` to `K_(2)MnO_(4)` :
`2MnO_(2) + 4KOH + O_(2) rarr 2KMnO_(4) + 2H_(2)O`
On passing current, the oxygen evolved at anode oxidises manganese into permangnate.
`2K_(2)MnO_(4) + H_(2)O + O rarr 2KMnO_(4) + 2KOH`
To oxidize manganate to permanganate, we can also use `CO_(2), CI_(2)` or `O_(3)` but not `H_(2)O_(2)` as it is relatively a weak oxidizing agent.
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Potassium permanganate is prepared by fusing pyrolusite with caustic potash in the presence of air or some oxidising agent which gives a green mass. The green mass is then extracted with water and treated with a current of Cl_2 to form potassium permanganate. In the laboratory, it is prepared by oxidising a manganese (II) salt by peroxosulphate. It acts as an oxidising agent in neutral, alkaline or acidic solutions. What type of hybridisation is involved in MnO_4^- ion and what is its structure?

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Assertion (A) : Pink coloured solution of potassium permanganate turns green on passing O_3 through it. Reason (R) : K_2MnO_4 is oxidised by O_3 to KMnO_4 .

Assertion: A pink coloured solution of potassium permanganate turns green on passing O3 through it Reason K_(2)MnO_(4) is oxidised by O_(3) to KMnO_(4) .

When MnO_2 is fused with KOH and KNO_3 , a coloured compound is formed. Choose the right compound with the appropriate colour.