jerryshizzle123 Posted April 28, 2009 Share Posted April 28, 2009 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...? Link to comment Share on other sites More sharing options...
UC Posted April 28, 2009 Share Posted April 28, 2009 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] Link to comment Share on other sites More sharing options...
vedmecum Posted April 28, 2009 Share Posted April 28, 2009 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 . Link to comment Share on other sites More sharing options...
John Cuthber Posted April 28, 2009 Share Posted April 28, 2009 IIRC the traditional choice of acid is CO2. It's cheap and essentially impossible to oxidise. Link to comment Share on other sites More sharing options...
jerryshizzle123 Posted May 3, 2009 Author Share Posted May 3, 2009 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? Link to comment Share on other sites More sharing options...
UC Posted May 3, 2009 Share Posted May 3, 2009 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. Link to comment Share on other sites More sharing options...
hermanntrude Posted May 3, 2009 Share Posted May 3, 2009 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. Link to comment Share on other sites More sharing options...
jerryshizzle123 Posted May 3, 2009 Author Share Posted May 3, 2009 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. Link to comment Share on other sites More sharing options...
hermanntrude Posted May 3, 2009 Share Posted May 3, 2009 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 Link to comment Share on other sites More sharing options...
jerryshizzle123 Posted May 4, 2009 Author Share Posted May 4, 2009 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. Link to comment Share on other sites More sharing options...
hermanntrude Posted May 4, 2009 Share Posted May 4, 2009 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. Link to comment Share on other sites More sharing options...
bob000555 Posted May 4, 2009 Share Posted May 4, 2009 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. Link to comment Share on other sites More sharing options...
UC Posted May 4, 2009 Share Posted May 4, 2009 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. Link to comment Share on other sites More sharing options...
jerryshizzle123 Posted May 4, 2009 Author Share Posted May 4, 2009 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. Link to comment Share on other sites More sharing options...
amit Posted May 7, 2009 Share Posted May 7, 2009 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- Link to comment Share on other sites More sharing options...
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