Gibbs free energy and voltage

[Hemichordate]

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In the equation deltaG = -nFE, my book says that n is the number of electrons transferred in the balanced redox reaction. But what if you have an equation like:

3Mg + 2Al(3+) ---> 3Mg(2+) + 2Al

Would it be n = 5 since Mg transfers 3 moles of electrons and Al transfers 2 moles of electrons?

 

[fizzgig]

My guess would be Al3+ takes 3 electrons per mol, 2 mols, so 6 electrons. Mg gives up 2 electrons per mol, 3 mols, so 6 electrons.

 

[GRod18]

yes n = 6 electrons.

Just look at the balanced half reactions.

If Al3+ gained 3 electrons per mole inorder to become Al (s)
then Mg would have lost 2 electrons per mole inorder to become Mg2+

in the balanced reaction, 2 moles of Al3+ gained 3 electrons each = 6 mole
in the balanced reaction, 3 moles of Mg lost 2 electrons each = 6 mole