I hope someone can clear this out for me. I find them a bit confusing and also a bit contradictory.
Basically, we all know that Eo is the standard redox potential relative to the Standard Hydrogen Electrode (SHE) with pH 0.0 and Eo' is the standard redox potential relative to the SHE with pH 7.0
For the reaction: 2H+ + 2e- = H2
Eo' = -0.42 V and this means that when we measure the redox potential of this (pH 7.0), we measure it relative to the SHE with pH 0.0
So from here, for example, the reaction: Fe3+ + e- = Fe2+ has Eo' = +0.77V means that the redox potential relative to SHE at pH 7.0 is +0.77V, which in turn means the redox potential relative to SHE at pH 0.0 is: +0.77 + (-0.42) = +0.35 V
My question is:
1) Is what I describe correct?
2) If its correct, then why in text book, they said for the reaction with iron above, Eo = +0.77V but NOT Eo'? Eo and Eo' should have different values? I have checked on the internet, some of the result say like text book, some say Eo' = 0.77V like me. Im confused this bit.
Can some one explain which is correct for me? Thank you so much.
Christian: Thank you very much for your answer. I see the bit about Fe3+, thanks!
But I just want to ask you 1 more question. If a reaction is dependent on H+ and we got the Eo' relative to pH 7 is x (because in biochemistry, we deal with systems at pH 7.0 rather than at pH 0.0), and we know the relative potential of H2 at pH 7.0 to SHE at pH 0 is y mV, then we can convert the Eo' above relative to pH 0 by either adding y to x, is that correct?
Christian Punckt Can you please tell me how can I convert standard reduction potential calculated at pH=7 to standard reduction potential at pH=0.
For example, I want to convert the standard reduction potential of C2H3O2- + 3H2O→CO2 + HCO3- + 8H+ + 8e- (which is -0.29V at pH=7) to standard reduction potential at pH=0.
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