JEE Main & Advanced Chemistry Electrochemistry / विद्युत् रसायन Cell Potential Or Emf Of The Cell

(1) “The difference in potentials of the two half – cells of a cell known as electromotive force (emf) of the cell or cell potential.”

The difference in potentials of the two half – cells of a cell arises due to the flow of electrons from anode to cathode and flow of current from cathode to anode.

\[Anode\underset{Flow\,\,of\,\,current}{\overset{Flow\,\,of\,\,electrons}{\longleftrightarrow}}Cathode\]

(2) The emf of the cell or cell potential can be calculated from the values of electrode potentials of two the half – cells constituting the cell. The following three methods are in use :

(i) When oxidation potential of anode and reduction potential of cathode are taken into account

\[E_{\text{cell}}^{0}=\] Oxidation potential of anode + Reduction potential of cathode \[=E_{\text{ox}}^{0}\,(\text{anode})+E_{\text{red}}^{\text{0}}(\text{cathode})\]

(ii) When reduction potentials of both electrodes are taken into account

\[=E_{\text{Cathode}}^{\text{0}}-E_{\text{Anode}}^{\text{0}}\]\[=E_{\text{right}}^{\text{o}}-E_{\text{left}}^{o}\]

(iii) When oxidation potentials of both electrodes are taken into account

\[E_{\text{cell}}^{o}=\] Oxidation potential of anode – Oxidation potential of cathode \[=E_{\text{ox}}^{0}(\text{anode})-E_{\text{ox}}^{0}(\text{cathode})\]      

(3) Difference between emf and potential difference

(4) Cell EMF and the spontaneity of the reaction :         We know, \[\Delta G=-nF{{E}_{cell}}\]