If I want to find the standard ΔG for a reaction in an electrochemical cell, I can use the equation ΔG° =-nFE° where n is the number of moles transferred, F is Faraday's constant, and E° is the standard emf of the cell. If I know the standard reduction potentials of the redox reactions happening in each half-cell, I can calculate the standard emf with the equation E°cell=E°reduction, anode-E°reduction, cathode. Standard reduction potentials are calculated under standard conditions, so all concentrations are at 1 molar. Now, consider the redox reaction:(adsbygoogle = window.adsbygoogle || []).push({});

2Fe^{3+}+ 2Cl^{-}---> 2Fe^{2+}+ Cl2

The two half reactions are:

2Fe^{3+}+ 2e^{-}---> 2Fe^{2+}

2Cl^{-}---> Cl2 + 2e^{-}

So if I calculate E°cell and want to use it to find ΔG°, I just have to determine the value of n, the number of moles of electrons transferred, and plug the values into ΔG° =-nFE°cell. Two electrons are transferred in the balanced equation above, so I could understand using n=2. However, this is the number of moles of electrons transferred for every 2 moles of Fe^{3+}and Cl^{-}that react, as you can see from the equation. I am trying to calculate the standard ΔG, in which all concentrations are 1 molar, so n=1, correct? 1 mole of electrons is transferred for every one mole of Fe^{3+}and Cl^{-}that react, and since we are dealing with concentrations of 1 molar, the "concentration" of electrons being transferred is 1 molar (I put concentration in quotes because the electrons themselves are dissolved in solution, but I refer to the number of moles in terms of concentration just to make my point clear.

So does anyone know if n should be 1 or 2? Thanks!

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# Electrochemistry question: n value in ΔG° =-nFE°cell

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