# Computational Chemistry Modelling Redox Potentials [closed]

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

• How good? It depends. How good is your voltage meter? see Nernst equation – MaxW Apr 19 at 19:28
• well this is not an electrochemistry question so im not using a voltmeter. Im using the Guassian 09 program. – Arqum Apr 19 at 20:05
• 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. – Greg Apr 19 at 21:11
• What resources do you have for this? Your personal computer? If so, how powerful is it? – Raphaël Apr 19 at 22:29
• Why is this "off-topic"? – 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.

Chemistry:

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

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.

• Question is about computational methods, not wet chemistry – Andrew Apr 19 at 23:00
• 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'! – AJKOER Apr 20 at 12:22
• 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? – AJKOER Apr 20 at 12:37
• 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. – Andrew Apr 20 at 13:21