Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: sweet_ana on January 09, 2007, 03:00:53 PM
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I have found somewhere a problem who sounds like this: "What volume of Na2S2O3 0.050 N is necessary to react completely with 0.0032 g KMnO4?" But I haven't found anywhere the reaction betwen them and experimentally I didn,t notice anything. Does anyone have any idea about it?
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the thiosulfate gets oxidised probably to sulfate (or just sulfite?)
permanganate gets reduced to MnO2 or Mn2+
this is a fairly complicated system and I don't think it's easy to tell the products. you would probably need to know the pH too
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KMnO4 + Na2S2O3 + H2O = K2SO4 + Na2SO4 + MnO2 + KOH
It has to be balanced, of course.
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Don't forget
S2O32- -> S4O62-
which is used for I2 determination. As FeLiXe stated - a lot depends on the redox potential (strongly pH dependent for permanganate) and reaction mechanism.
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Don't forget
S2O32- -> S4O62-
which is used for I2 determination. As FeLiXe stated - a lot depends on the redox potential (strongly pH dependent for permanganate) and reaction mechanism.
Could be, of course.
Mind you, looking at sweet_ana's question, aren't you tempted to answer 2 KMnO4 + Na2S2O3-> 2 NaMnO4 + K2S2O3 too?
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Mind you, looking at sweet_ana's question, aren't you tempted to answer 2 KMnO4 + Na2S2O3-> 2 NaMnO4 + K2S2O3 too?
That's ridiculous :) I am sure the question is about redox reaction.
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KMnO4 + Na2S2O3 + H2O = K2SO4 + Na2SO4 + MnO2 + KOH
It has to be balanced, of course.
I think theoretically it is possible, but I tried it experimantally (just mixing the solutions, without heating, but KMnO4 doesn't need temperature to reduce to MnO2) and no precipitate appeared.
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Hmm..
I havent got all the ins and outs of this but:
8 MnO4 - + 3 S2O32- + 2 H+ --> 6 SO42- + 8 MnO2 + H2O
Should run okay in Acidic Solution, probably have to warm it a bit, to get the Lillac to blackish color change.
As MnO4- is a strong oxidizing agent i doubt that the reaction:
S2O32- -> S4O62- is going to be stable, it will probably be oxidized SO42-
Also, most redox reactions go a lot smoother with added heat...
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As MnO4- is a strong oxidizing agent i doubt that the reaction:
S2O32- -> S4O62- is going to be stable, it will probably be oxidized SO42-
Well, original question doesn't contain information about pH, so we don't really know what will be the Mn containing product - it can be Mn2+, MnO2 or even MnO42-. In every case oxidizing strength (redox potential) of MnO4-/something system will be different. That's not to say that S4O62- is THE product, I just don't see any reason to assume it is not :)
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Well, original question doesn't contain information about pH, so we don't really know what will be the Mn containing product - it can be Mn2+, MnO2 or even MnO42-. In every case oxidizing strength (redox potential) of MnO4-/something system will be different. That's not to say that S4O62- is THE product, I just don't see any reason to assume it is not :)
I have posted the original problem where I found the reaction, and there is no information about the pH. However, since the solutions are just mixed and no acid or base is present, I think the pH is 7.
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Permanganate reacts with thiosulfate with acidic or basic solution. Thiosulfate is oxidised to sulfate or tetrathionate (Na2S4O6), respectively.