Galvani Potential of the Hydrogen Electrode

Based on Chapter 1, the Gibbs energies of formation of gaseous hydrogen and aqueous proton are defined as follows  

Now the Galvani potential of the hydrogen electrode Atp can be referred to as the (equilibrium) potential of the hydrogen electrode, fi eqflVHj experimentally defined as follows  

Equation 4.12 represents the well-known Nemst equation for the hydrogen electrode corresponding to the following reduction half-reaction  

In conclusion, the Galvani potential of the hydrogen electrode defined by Equations 4.12 and 4.13 can experimentally be measured in dilute aqueous solutions at a relatively low pressure of hydrogen to accurately define flir -(aq) and aH2(g) in Equation 4.12 and, then, to carry out an extrapolation to the infinitely dilute solution to provide the standard state conditions of flH2(g) = n+(aq) = 1- 

---