A button cell used in watches functions as following

Zn(s) + Ag2O(s) + H2O(l) 2Ag(s) + Zn^2 + (aq) + 2OH^-(aq) If half cell potentials are: Zn^2 + (aq) + 2e^-→ Zn(s); E^∘ = - 0.76 V Ag2O(s) + H2O(l) + 2e^-→ 2Ag(s) + 2OH^-(aq), E^∘ = 0.34 V The cell potential will be: