Hydrogen, electrode standard free energy

It has been mentioned that = E when the reference system is the oxidation of molecular hydrogen to solvated (hydrated) protons. The standard electrode potential of the hydrogen electrode is chosen as 0 V. Thermodynamically it means that not only the standard free energy of formation of hydrogen (/r ) is zero - which is a rule in thermodynamics (see Table 2) - but also that of the solvated hydrogen ion /U.S+ = O . (The old standard values of were calculated using = atm = 101325 Pa. The new ones are related to 10 Pa (1 bar). It causes a difference in the potential of the SHE of -i- 0.169 mV, that... 

Since in experiments such as the one we have just discussed, it is only possible to determine potential differences between two electrodes (and not the absolute potential of each half cell), it is now useful to choose a reference system to which all measured potential differences may be related. In accord with the IUPAC 1953 Stockholm convention, the standard hydrogen electrode (SHE) is commonly selected as the reference electrode to which we arbitrarily assign a zero value of electrical potential. This is equivalent to assigning (arbitrarily) a standard free energy change, ArG°, of zero at all temperatures to the half reaction ... 

The standard free energy of formation of gaseous hydrogen chloride is — 22 770 cal mob and the standard potential of the calomel electrode is 0.268 0 V. 

The activity is a function of the coverage 0 of the electrode surface with H atoms. The coverage will depend upon the nature of the electrode material because of /Zo,h- The standard free energy dGo,H of hydrogen adsorption is related to /Zo,h-... 

Initially, it is noted that by definition, the standard free energy Gfgs for H+(aq,c ) and for H2(g,p ) is given the value OkJ/mol for the standard hydrogen electrode, therefore, the following condition applies... 

The standard Gibbs free energy change per mole accompanying vaporization (the conversion of a substance from the liquid state into the vapor state), standard hydrogen electrode (SHE) A hydrogen... 

---