Application of EMF Measurements

Application of EMF Measurements

Determination of Equilibrium Constant

Measurement of the standard Emf of the cell, E°Cell, enables one to evaluate the equilibrium constant for the electrode reaction.
The relation between the standard free energy change and the equilibrium constant of a reaction is given by:
G0= -RT In K
But the standard free energy is related to the standard electrode potential by the expression:
G0 = -nE0F
 Hence
E0 = In K
At 298K
E0 = log K                                                                                                                  
Exercise 4
For the following electrochemical cell
Zn/Zn2+//Fe3+,Fe2+/Pt
Whose standard Emf is 1 .534V, the overall cell reaction is
Fe3 + + 1/2Zn  Fe2+ +1/2 Zn2+

Calculate the equilibrium constant

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