Thermodynamic Reference Level for Ions

The ion level in condensed phases has been represented by the real potential, a, referred to the standard gaseous state of the ion at the outer potential of the condensed phases. The reference level, then, is not common to all ions but differs with different ions. In chemical thermodynamics, the conventional energy scale is based on the assumption that all atoms in the stable form in the standard state are at the zero energy level, which is the thermodynamic reference level of energy for chemical substances. In the following, we discuss the relationship between the scale of the ion level represented by the real potential of ions and the conventional energy scale of particles in chemical thermodynamics. 

We consider, as an example, a gaseous hydrogen ion (proton) in the standard state, whidi is at the reference zero of proton level. The ionization of gaseous hydrogen molecule in the standard state to produce a standard gaseous proton is shown in Eqn. 3-47  

The chemical thermodynamic energy scale of ions described in this section is not the same as the conventional energy scale of hydrated ions in aquatic electrochemistry (Refer to Sec. 6.4.) the conventional scale is referred to the ion level of hydrated proton of unit activity. 

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