A button cell used in watches functions as following: Zn(s) + Ag₂O(s) + H₂O(l)⇌2Ag(s) + Zn²⁺(aq) + 2OH⁻(aq) If half cell potentials are: Zn²⁺(aq) + 2e⁻→Zn(s); E° = -0.76V Ag₂O(s) + H₂O(l) + 2e⁻→2Ag(s) + 2OH⁻(aq), E° = 0.34V The cell potential will be:

The cell reaction is as given below.
Zn(s) + Ag₂O(s) + H₂O(l)⇌2Ag(s) + Zn²⁺(aq) + 2OH⁻(aq)
The half cell potentials are as given below.
Zn²⁺(aq) + 2e⁻→Zn(s); E° = -0.76V
Ag₂O(s) + H₂O(l) + 2e⁻→2Ag(s) + 2OH⁻(aq), E° = 0.34V
The expression for the cell potential is
E°cell = E°cathode - E°anode
Substitute values in the above expression:
E°cell = 0.34 - (-0.76) = 1.1V
Thus, the cell potential will be 1.10 V.