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Question
What is the relationship between Gibbs free energy of the cell reaction in a galvanic cell and the emf of the cell? When will the maximum work be obtained from a galvanic cell?
Solution
Electric work is the product of total charge and cell potential.
Wmax = nF × Ecell
But according to thermodynamics,
Wmax = - Δ G
The formula for Gibbs free energy is given by:
Δ G = - nFEcell
where G is the Gibbs energy, Ecell is the emf of the cell, −nF is the amount of charge.
When the concentration of each reacting component is unity, the above equation changes to:
ΔG0 = - nF × `"E"_"cell"^0`
From the above formula, we understand that the reduction in Gibbs energy results in the reversible work done by the galvanic cell.
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