I am given the reduction potential of $\ce{Fe^{3+}}$ to $\ce{Fe^{2+}}$ as well as the dissociation constants $\ce{K_D}$ for a $\ce{Fe^{3+}}$ complex and a $\ce{Fe^{2+}}$ complex (effectively, the ratio of concentrations of the $\ce{Fe^{3+}}$ complex and $\ce{Fe^{2+}}$ complex, if I divide one constant by the other).
I need to find the reduction potential of the $\ce{Fe^{3+}}$ complex.
How would I go about this?
Is it possible that I could use the reduction potential of $\ce{Fe^{3+}}$ to $\ce{Fe^{2+}}$ as an estimate for that of the $\ce{Fe^{3+}}$ complex, and then use the Nernst equation to plug in the concentrations of the two complexes? Or is there no guarantee that these two potentials would be close?

Specifically, these are iron-siderophore complexes.

  • $\begingroup$ You should try to see if you can write a combination of the reactions you are given that added together will give the reaction of reducing the complex. $\endgroup$ – Tyberius Dec 3 '17 at 19:06
  • $\begingroup$ Thank you!!! I don't know why I couldn't see the solution to this!! $\endgroup$ – HBHSU Dec 3 '17 at 19:14
  • $\begingroup$ no problem! If you are working with redox problems, you should always be on the lookout for ways to combine equations. $\endgroup$ – Tyberius Dec 3 '17 at 19:17

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