(1)
(a) : Measurement of single electrode potential
(b) : Measurement of cell potential According to Nemst theory, electrode potential is the potential difference between the metal and ionic layer around it at equilibrium, i.e. the potential across the electric double layer.
(2) For measuring the single electrode potential, one part of the double layer, that is metallic layer can be connected to the potentiometer but not the ionic layer. Hence, single electrode potential can’t be measured experimentally.
(3) When an electrochemical cell is developed by combining two half cells or electrodes, they can be connected to the potentiometer and the potential difference or cell potential can be measured.
\(E_{cell} = E_2 - E_1\)
where E1 and E2 are reduction potentials of two electrodes.
