Calculation of the energy change involved in chemical reactions occurring irreversibly

The overpotential of electrochemical reactions has a parallel in thermal reactions which may be called the overstress. This quantity must be added algebraically to the free-energy change of reversible thermodynamics if one is to know the energy needed to carry out a reaction at a finite velocity or to find out the energy obtainable from a reaction occurring spontaneously. For a velocity of ν, and outside the quasi-reversible region dealt with in irreversible thermodynamics, the overstress at a velocity ν is related to this velocity, and to the equal and opposite velocities at equilibrium, ν_o, by the equation

$\text{ΔΔF}{}_{\mathrm{(v)}}\text{=}\text{RT}\text{β}\text{ln}\text{v}\text{v}{}_{\mathrm{a}}$

where β is Bronsted's coefficient. Such considerations may alter the relative economic desirability of competing chemical processes, e.g. in water splitting, as well as reducing the desirability of chemical, compared to electrochemical, paths.