Question

When two half cells X and Y combined then the standard cell potential of cell is.

• A. $E_X+E_Y$
• B. $E_X^0+E_Y^0$
• C. -($\Delta G_X^0+\Delta G_Y^0$)/nF
• D. $\Delta G_X^0+\Delta G_Y^0$

Answer 1

The correct option is C -($\Delta G_X^0+\Delta G_Y^0$)/nF

EMF is an intensive property, the cell potential of two half-cells cannot be added. To calculate the cell potential of a cell we need to sum up the Gibbs free energy changes of the two the half cells.

$\Delta G_{cell}^0=\Delta G_X^0+\Delta G_Y^0$
we know that
$\Delta G^0=-nF{E}^0$
thus $E^0=-\frac{\Delta G_X^0+\Delta G_Y^0}{n_{rxn}F}$