2.3 Electromotive Series [1/2]

In an electromotive force series (Table 2.1), the potentials of pure metals are listed in accordance with their tendencies to corrode, the metals with the most positive potentials on the top  (like Ag, Au, Pt, etc.) followed by metals with negative potentials in the decreasing order (Na, Mg, K, etc.). The potentials listed in the table given below are called "Standard Reduction Potentials" as the half cell reaction are written in the reduction form (Au³⁺ + 3e^- Au). Chemists generally use the emf series in which potentials are written as oxidation reactions (Au Au³⁺ + 3e^-), and they are termed as "Standard Oxidation Potentials". The standard potentials (E^o) are measured against a standard hydrogen electrode which is at 1 atm pressure and the H⁺ concentration is 1 molar. The standard hydrogen electrode has been assigned a potential of 0 V at 25^oC. 

Table 2.1: Standard Oxidation-Reduction Potentials, Volts (25^oC, against Normal Hydrogen Electrode)

The method of measurement is shown below.