Question

The voltage of the cell combination of Cu/Cu2+ and Zn/Zn2+ is 0.953V. The standard reduction potential for Cu/Cu2+ is expected to be 0.34V. Determine the reduction potential for Zn/Zn2+

Answer 1

Sol.   

Half - cell reaction at anode :

Zn ----> Zn2+ + 2e- ,

Standard Reduction potential at anode =  E°anode = ?

Half - cell reaction at cathode :

Cu2+ + 2e- ----> Cu   ,

Standard Reduction potential at cathode = E°cathode = + 0.34 V  

So , Overall cell reaction :

Zn + Cu2+ ----> Zn2+ + Cu ,

Standard Reduction potential of cell = E°cell = + 0.953 V

Therefore , E°cell = E°cathode - E°anode

0.953 = 0.34 - E°anode  

and , E°anode = 0.34 - 0.953 = - 0.613 V

Hence , Standard reduction potential for Zn/Zn2+

is  - 0.613 V