Potassium manganate --> Potassium permanganate HELP

[jerryshizzle123]

I have some potassium manganate that I'd like to convert to the permanganate, but so far, every single one of my attempts has failed. I heard about electrolysis of the solution, but all it ended up producing was manganese dioxide. Any suggestions...?

[UC]

Add a weak acid like vinegar to bring the pH down and it will disproportionate to manganese dioxide and permanganate. Isolating it will be a pain in the arse. If you're a bit suicidal, you can bubble chlorine through the solution, but I seriously do not recommend that. Seriously.

 

[ce] 4H^+ + 3MnO4^2^- -> 2MnO4^- + MnO2 (s) +2H2O [/ce]

 

[ce] 2MnO4^2^- +Cl2 -> 2MnO4^- + 2Cl^- [/ce]

[vedmecum]

hi jerryshizzle123 , you said that u end up with MnO2 , these may be because of reaction condition which you had taken .

 

Potassium permanganate is manufactured on a large scale from manganese dioxide, which is fused with potassium hydroxide and heated in air or with potassium nitrate (a source of oxygen). This leads to the formation of potassium manganate, which on electrolytic oxidation in alkaline solution gives potassium permanganate.

 

MnO2 + 2OH− + O2 → MnO42− + H2O

 

so instead of taking acidic medium try basic medium so in case MnO2 form , it will further electrolyzed to KMnO4 .

[John Cuthber]

IIRC the traditional choice of acid is CO2. It's cheap and essentially impossible to oxidise.

[jerryshizzle123]

Bubbling chlorine through the solution seems like it can be effective (I haven't tried it yet). Can anyone tell me why it is dangerous?

[UC]

Bubbling chlorine through the solution seems like it can be effective (I haven't tried it yet). Can anyone tell me why it is dangerous?

 

The fact that you don't know means you shouldn't even think about it. Just read the wiki article. I suspect that has enough info.

[hermanntrude]

Bubbling chlorine through the solution seems like it can be effective (I haven't tried it yet). Can anyone tell me why it is dangerous?

 

also read this This document is something you shoudl be famliar with if you work with chemicals ever, even just at home for fun. It's called a material safety data sheet and contains all the things you need to know before using a chemical. The one for chlorine is quite startling. it's very dangerous stuff.

[jerryshizzle123]

If chlorine gas is the only presented hazard, I might as well carry on with the procedure. I've worked with chlorine gas enough to know its properties and how to use it safely. I was implying that some potentially explosive or toxic product would be formed.

[hermanntrude]

hmm well i'm not sure how violent the reaction might be... it is a mixture of a fairly strong oxidising agent and a reducing agent

[jerryshizzle123]

And I ask, which of the following is the reducer strong enough to react with chlorine violently: K2MnO4, KMnO4, or MnO2? If I recall correctly, they're all oxidizing agents.

[hermanntrude]

What exactly do you want to hear? if you want our permission or agreement on your chosen method, you won't get it. Our hazmat policy doesnt allow us to recommend a dangerous procedure. I've used chlorine myself but i have a fume hood, and even then it gave me a sore throat for a day or so. And as UC said, you'd still end up with a nasty mixture which will be hard to separate. Give it up and buy some. buy a chemistry set... they always have KMnO4 in them anyway.

[bob000555]

buy a chemistry set... they always have KMnO4 in them anyway.

 

Most chemisty sets havent included KMnO4 for years. It's part of why kids find science boring now; the most interesting chemical their ever alowed to touch is Na2CO3 or somesuch.

[UC]

Hrm. Now that I think about it, nevermind. Chlorine won't work anyway. The oxidizing potential of permanganate is too high. If you make the solution acidic, [ce] Cl^- [/ce] will take it all the way down to [ce] Mn^2^+ [/ce]. [ce] MnO2 [/ce] with hydrochloric acid was an old way to generate chlorine gas. in basic solution, it will remain as manganate.

[jerryshizzle123]

What exactly do you want to hear? if you want our permission or agreement on your chosen method, you won't get it.

 

I never implied that I needed your approval. I don't, however, need to hear sarcasm, especially when it's neither warranted nor accurate.

[amit]

standard potential for reaction

Cl2(g) + 2 e− ⇄ 2 Cl− +1.36

MnO4− + H+ + e− ⇄ HMnO4− +0.90

 

therefore free energy change for above reactions coupled should be

-(2*1.36*F - 2*.9*F) (G=-nFE)

= -2*.46*F

 

as the above value is -ve hence i believe

 

2MnO42-+2Cl2=Mno4-

is thermodynamically possible (dont know about practical implications)

is there something wrong in my calculations?

in lab we used PbO2 for qualitative identification of Mn2+ as solution turned pink due to formation of MnO42-