Equilibrium Constant and Nernst’s Equation: The e.m.f. of the cell maybe used to calculate the equilibrium constant for the cell reaction. At equilibrium, the electrode potentials of the two electrodes become equal so that e.m.f. of the cell is zero. Consider the following redox reaction: Zn(s) + Cu2+(aq) ———-> Zn2+(aq) + Cu(s)
Let us assume that the concentrations of Zn2+(aq) and Cu2+(aq) are equilibrium concentrations and the equilibrium constant, Kc is
The Nemst’s equation for above reaction is—
At equilibrium, Ecell = 0, then above equation becomes
