kyro8008 - 22-2-2006 at 15:29
I recently performed an interesting experiment as follows:
1g of NaOH was dissolved in 50ml of water and a small crystal of potassium permanganate was added giving a purple solution. I passed this solution
through a filter paper and the solution turned green. The explanation given was "it was reduced from KMnO4 to K2MnO4".
Can anyone explain why this is? Does the paper reduce the permanganate? Or is another effect at work here?
Thankyou for any help!
guy - 22-2-2006 at 16:09
Yes it reduced something in the paper, thats the only explanation
12AX7 - 22-2-2006 at 19:41
As I recall, Mn(6+) to Mn(7+) and vice versa is pretty easy, either by adding or giving off oxygen. The oxygen could be given off by burning
(oxidizing) the paper slightly, too. (You wrote "reduced something in the paper", erm, mistake?)
Tim
guy - 22-2-2006 at 20:14
O yeah thats a mistake, it should be oxidized. Also MnO4 2- to MnO4 - can be done by adding H+. It even works if the H+ is from bicarbonate MnO4 2-
+ H+ <--> MnO4- + MnO2 + H2O.
kyro8008 - 24-2-2006 at 11:52
Thanks everyone, thats cleared it up a bit, alot of the transition metals seem to have odd properties with air, etc.
woelen - 26-2-2006 at 06:25
If you add MnO4(-) to a strong solution of NaOH, then it decomposes, giving off oxygen and it goes to the +6 oxidation state, forming the green
MnO4(2-) ions. So, you do not need a reducing agent to make MnO4(2-) from permanganate.
I have made pictures of this:
http://woelen.scheikunde.net/science/chem/solutions/mn.html