[THC]

Hi, could someone help me with this one?

Q: Balance the half-reaction and calculate the standard electrode potential:
S2O3^2- -> SO4^2-

A:
I'm pretty lost. I tried to look it up, but I can't find a reaction where S2O3^2- and SO4^2- are in the same reaction.

Anyways, I think it's in an alkaline solution (wouldn't make sense if it's acidic), so
S2O3^2- + 10 OH- -> 2 SO4^2- + 5 H2O + 8 e-

Is this correct?
How do I calculate the electrode potential - Gibbs energy and -dG = n*F*E^o?

[champ]

 u r right and u can calculate Electrode potential: Delta G^o= -nFE^o
First Calculate delta G^o using the data which i am sure is giving to u in your book. then use the equation to solve for E^o.


gud luck...

[THC]

u r right and u can calculate Electrode potential: Delta G^o= -nFE^o
First Calculate delta G^o using the data which i am sure is giving to u in your book. then use the equation to solve for E^o.


gud luck...

Okay, I found out that was wrong. You can't find the Gibbs energy for an electron anyway

Instead, I thought about combining different half cell reactions.
I found this:

2 H2SO3 + 4 e- + 2 H+ <--> S2O3^2- + 3 H2O
E^o  = 0.40 V

SO4^2- + 4 H+ + 2 e- <--> H2SO3 + H2O
E^o = 0.158 V

So if I combine these, I end up with something like

S2O3^2- + 5 H2O <--> SO4^2- + 8 e- + 10 H+

(I reverse both and multiplied the last one with 2).

Does this seem ok? The question now is - how do I calculate E^o for this reaction?

[THC]

Ok, I thought about using dG^o = n*F*E^o, because dG for the reaction must be the sums of the individual reactions - kinda like Hess' law, only with Gibbs energy. I don't know if this works - could somebody give me a hint or two?