How could I accurately determine the Fe3+/Fe2+ redox potential in an aqueous solution? What would be a good computational model(s) for this?

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    $\begingroup$ How good? It depends. How good is your voltage meter? see Nernst equation $\endgroup$ – MaxW Apr 19 at 19:28
  • $\begingroup$ well this is not an electrochemistry question so im not using a voltmeter. Im using the Guassian 09 program. $\endgroup$ – Arqum Apr 19 at 20:05
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    $\begingroup$ You have to calculate the free energy difference of the corresponding redox equation and that is it. You will have a smaller and bigger error, how you treat solvent effects and similar details. $\endgroup$ – Greg Apr 19 at 21:11
  • $\begingroup$ What resources do you have for this? Your personal computer? If so, how powerful is it? $\endgroup$ – Raphaël Apr 19 at 22:29
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    $\begingroup$ Why is this "off-topic"? $\endgroup$ – user1271772 Apr 20 at 1:30

Here is a non-electrolysis scenario that could be of interest. Add deoxygenated water to FeCl2 in a closed vessel filled with oxygen or air. Record the oxygen consumption.


$\ce{4 Fe(2+) + 2H2O + O2 (g) -> 4 Fe(3+) + 4 OH- }$

The wet ferrous chloride should be presented in a fashion to maximize oxygen exposure from air.

[EDIT] I would also place the system (till the reaction is completed) under pressure to limit adjustments owing to the speed of oxygen assimilation.

To be clear, as apparently required by a comment, the purpose of this experiment, per my understanding of the Question, is to serve as a frame for real world validation of a sophisticated theoretical/computational based model.

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    $\begingroup$ Question is about computational methods, not wet chemistry $\endgroup$ – Andrew Apr 19 at 23:00
  • $\begingroup$ Actually to quote a source: "A new Gaussian MCTDH program: Implementation and validation on the levels of the water and glycine molecules." So, as I understand it and the Question (perhaps needing more specificity), there is an underlying frame (aka a redox reaction) to serve as the basis for computations. Also, if purely theoretical, why is Arum asking non-computational chemists for help? If someone else has other suggested redox involving Fe2+/Fe3+ that are more simple than mine, I would like to review them (as would Arum, I suspect). Also note the word 'validation'! $\endgroup$ – AJKOER Apr 20 at 12:22
  • $\begingroup$ Could someone sincerely explain how to accomplish validation (via measuring?) of a computational analysis without ever departing from the theoretical realm? My supposition is a 'real' world redox to examine, perhaps even mine? $\endgroup$ – AJKOER Apr 20 at 12:37
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    $\begingroup$ In general, computational chemistry lags far behind experimental chemistry. There is already a wealth of experimental data regarding the Fe2+/Fe3+ couple. Initial validation of a computational model would simply be showing that it can recapitulate already known experimental results. $\endgroup$ – Andrew Apr 20 at 13:21

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