At anode :
Ag+Cl−→AgCl+e−
At cathode:
AgBr+e−→Ag+Br−
E=E∘Ag/AgCl/Cl−+E∘Br−/AgBr/Ag−0.0591log[Br−][Cl−]
....(i)
For reaction :
Ag+Cl−→AgCl−e−
Ag++e−→Ag
E=O=E∘Ag/AgCr/Cl−+E∘Ag+/Ag−0.0591
log1[Ag+][Cl−]
E∘Ag/AgCr/Cl−=E∘Ag/Ag+−0.0591logKsp(AgCl) ....(ii)
for reaction
AgBr+e−→Ag+Br−
Ag→Ag++e−
E=0=E∘Br−/AgBr/Ag+E∘Ag/Ag+−0.0591log[Ag+][Br−]
E∘Br−/AgBr/Ag=E∘Ag+/Ag+0.0591logKsp(AgBr) ...(iii)
from equation (1), (2) & (3)
E=0.0591logKsp(AgBr)Ksp(AgCl)−0.0591log[Br−][Cl−]
E=0.0591log3.3×10−13×0.22.8×1010×0.001=−0.037V