Question

the E°values of cu2+/cu and ag+/ag electrodes are 0.34 v and 0.80 v r.p. for what concentration of ag+ions will the emf of cell at 25°c be zero?the concentration of cu2+ions is given as 0.01M.​

Answer 1

Answer: The redox reaction taking place in the cell is

Cu(s)+2Ag+(aq)→Cu2+(aq)+2Ag(s)

According to Nernst equation :

E cell=E∘cell−0.0591nlog[Cu2+(aq)][Ag+(aq)]2

E cell=0,E∘cell=E∘(Ag+/Ag)−E∘(Cu2+/Cu)=0.80−0.34=0.46 V,

[Cu2+(aq)]=0.01M

Substituting the values in the equation,

0=0.46−0.05912log(0.01)[Ag+(aq)]2

log0.01[Ag+(aq)]2=2×0.460.0591=15.567

0.01[Ag+(aq)]2=anti log 15.567=3.69×1015

[Ag+(aq)]2=0.013.69×1015=2.71×10−17

[Ag+(aq)]=(2.71×10−17)1/2=(27.1×10−18)1/2=5.21×10−9M.