Table 22.1 lists the standard electrode potentials of a number of half cells. In the standard electrodes, species in all forms (solids, liquids or gases) are present with unit activities, i.e., in their standard states. It is to be noted that emf is an intensive property and that the half cell 2H+ + 2e H2 (g) will have the same emf as eq (22.3) but the free energy change for this reaction will be twice the value for eq. (22.3), because rGo = - nFo and rGo is an extensive property depending on the number of moles of electrons transferred.
Table 22.1 Standard electrode potentials at 298.15 K
H2 (g) will have the same emf as eq (22.3) but the free energy change for this reaction will be twice the value for eq. (22.3), because 
rGo = - nF
o and 
