This indicates that equilibrium has been
attained In this situation the Nernst equation may be written as:
E(cell) = 0 = 
(
)
o
Ecell
 – 
2 303
2
log [Zn
]
[Cu
]
2
2
RT
F
+
+
or 
(
)
o
Ecell
 = 
2
2
2 303
[Zn
]
log
2
[Cu
]
RT
F


But at equilibrium,
[
]
[
]
Zn
Cu
2
2
+
+  = Kc for the reaction 2