Ag(s)|AgNO3(aq, C1 M)||AgNO3(aq, C2=0.2 M)|Ag(s)
For the given cell representation, the cell reaction will be,
Ag+(aq, C2=0.2 M)→Ag+(aq, C1 M)
For concentration cell, we know that,
Ecell=E0cell−0.0591nlog[C1][C2]
Ecell=E0cell+0.0591nlog[C2][C1]
For concentration cells, cathode and anode consist of same metal and its solution.
Thus,
E0=0
0.8=0.05911log [0.2][C1]
0.80.0591=log [0.2]C1
13.5≈log [0.2]C1
Antilog (13.5)=0.2C1
3.16×1013=0.2C1
C1=0.063×10−13M
C1=0.63×10−14M