Free Energy and Cell Potential
The relation linking the Gibbs energy change of a cell reaction to the electromotive force it generates.
Formula / equation
ΔG = −nFE
Unit
kJ/mol
In depth
The relation shows that a positive cell potential corresponds to a negative free energy change and hence a spontaneous reaction. It also means a measured voltage yields ΔG directly, and combined with ΔG° = −RT ln K it gives equilibrium constants from a simple voltmeter reading.
Examples in the real world
The Daniell cell's 1.10 V corresponds to ΔG° = −212 kJ/mol for the zinc–copper reaction.