Electrochem help!!!! (Redox)

[alphatarget1]

Took chemistry 3-4 years ago, I'm trying to figure out this really simple equation.

Fe 2+ + 3 OH - = Fe(OH)3 + e-

E0 = -1.313V

I need to figure out the Redox Potential, so I'm going to use this equation:

E = E0 + (0.059/n) * log (Ox/Re d)

Concentration is given for Fe 2+ at 10^-4 mol/l

It's a really simple calculation, the problem is that I don't know the concentration of 3 OH-. The solution states that it's 10^-7 but I don't know how they got to that. It's the only part I'm stuck on. Any help is appreciated!

 

[Ika]

10^-7 looks like the OH- concentration in a pure water solution. someone correct me if i'm wrong, though.

 

[alphatarget1]

Originally posted by: Aflac
10^-7 looks like the OH- concentration in a pure water solution. someone correct me if i'm wrong, though.

D'oh! that explains it... Thanks!!!!

 

[iwantanewcomputer]

yay, i knew that. I just didn't bother learning the electrochem stuff in AP chem in HS, and haven't needed it in chemical engineering schedule

 

[Ika]

Originally posted by: iwantanewcomputer
yay, i knew that. I just didn't bother learning the electrochem stuff in AP chem in HS, and haven't needed it in chemical engineering schedule

you don't need to know Kw = Ka/Kb?? 😕