EMF of electrochemical cell in the standard state

The electrochemical cell consists of two half cells where one of the half-cell has a higher value of reduction potential as compared to the other. As a result of this potential difference, there is a flow of electrons from the electrode with a lower reduction potential (or higher oxidation potential) to the electrode with higher reduction potential (or lower oxidation potential). The difference between the electrode potentials of the two electrodes in the electrochemical cell is known as electromotive force or cell potential of a cell. The electromotive force is commonly abbreviated as EMF (emf) and is expressed in volts. The emf of a cell may be expressed in terms of the difference in the reduction electrode potential.

EMF = E_{substance reduced} - E_{substance oxidized}

EMF= E_R - E_L or EMF= E_cathode - E_anode

where E_R and E_L represent electrode potential of electrode on right hand side and on the left hand side respectively. It depends upon the nature of the electrodes and the concentration of the solutions in the two half-cells.

Difference between EMF and potential difference