ABSTRACT

The equilibrium at the electrode may be disturbed by making it more oxidizing or reducing by superimposing an external emf. The internationally agreed standard is the hydrogen electrode; this device operating with hydrogen gas at 1 atmosphere pressure, in contact with platinized platinum, in a solution of hydrogen ions of unit activity, is assigned a potential of zero at all temperatures. Electron exchanges will occur between the highest available energy level in the electrode and the lowest energy orbitals of the solute species. The electrode which has the more negative potential is always written on the left as the negative pole of the cell, while that with the more positive electrode potential is always written on the right as the positive pole of the cell. Owing to the precision with which electrochemical measurements may be made for such systems, it is often possible to use them to obtain precise thermodynamic data characteristic of the reactions occurring within cells.