# Calculating ξ° value for a galvanic cell

Calculate the ξ° value for the galvanic cell:
IO3(aq) + Fe2+(aq) <--> Fe3+(aq) + I2(aq)

So I found the half reactions to be:

5Fe2+(aq) --> 5Fe3+(aq) + 5e- Reducing agent 0.77V
6H+(aq) + 5Fe2+(aq) + 5e- --> I2(aq) + 3H2O Oxidizing agent

The problem I have is that I can't find the standard reduction potential for the cation's half reaction. Do I just use the potential for I2(s) + 2e- --> 2I- or this something special that I'm missing?

Thanks!

Borek
Mentor
Calculate the ξ° value

ξ°? and not E0?

IO3(aq) + Fe2+(aq) <--> Fe3+(aq) + I2(aq)

IO3(aq)? and not IO3-?

It can be difficult to not reduced iodine further to I- in the presence of Fe2+, but perhaps with right stoichiometry reaction will stop at I2.

5Fe2+(aq) --> 5Fe3+(aq) + 5e- Reducing agent 0.77V

Why 5?

6H+(aq) + 5Fe2+(aq) + 5e- --> I2(aq) + 3H2O Oxidizing agent

This is completely off - please check if that's what you meant.

The problem I have is that I can't find the standard reduction potential for the cation's half reaction.

Not surprising - reaction you wrote doesn't make sense.