Meena - 27-2-2006 at 15:22
Hello. I have a course work where I have to give a balanced equation of reduction of Fe(III) to Fe(II) with Na2S2O4. Could anyone help me??? Cheers.
Meena
12AX7 - 27-2-2006 at 15:57
Well look at the state of the sulfur atom. Balancing equations is easy enough that you don't need help there.
Tim
unionised - 28-2-2006 at 12:37
I did think about the state of the sulphur atom; in fact I thought about both atoms. Then I thought about what state they end up in.
Unfortunately, since the question doesn't tell me what oxidation state they end up in I still can't answer the question.
In principal, I guess I could look up a few tables of oxidation potentials but, since the pH isn't given - nor are the concentrations etc, I really
don't think it's possible to answer the question as it stands.
Since I'm a professional chemist who can't answer the question and this is the beginner's thread I can't help thinking your reply is a bit less
helpful than it might have been.
Also, I think your last sentence is simply incorrect. If your assertion "Balancing equations is easy enough that you don't need help there." were
true then presumably Meena wouldn't have asked for help.
12AX7 - 28-2-2006 at 13:05
Ya. That's one of those human things, where you attempt to embarrass the person into doing the grunt work of it. 
Tim
woelen - 28-2-2006 at 14:54
Dithionite is a strong reductor, which however behaves really bad from the point of view of stoichiometry. The dithionite can be oxidized to sulfite
(or SO2 in acidic media), thiosulfate, sulfate or tetrathionate. The precise oxidation product strongly depends on pH. There usually also are side
reactions, in which sulphur is formed, especially in acidic solutions.
If you mix a salt of Fe(3+) with a solution of sodium dithionite, without added acid, then I expect a lot of crap, containing S, FeS, Fe(2+) in
solution, SO3(2-), S2O3(2-), SO2, S4O6(2-) and who knows what more.
I've done quite some experiments with dithionite and it only is useful as a qualitatively strong reductor, but quantitatively it is totally useless,
due to all the above-mentioned reactions which can occur.