A button cell used in watches, functions as following Zn(s)+Ag2O(s)+H2O(l)⇌2Ag(s)+Zn2+(,)+2OH−(aq)If half-cell potentials are Zn2+(aq)+2e−⟶Zn(s);E∘=−0.76VAg2O(s)+H2O(l)+2e−⟶2Ag(s)+2OH−E∘=0.34V the cell potential will be

Anode is always the site of oxidation and cathode is the site of reduction, Thus, anode half-cell isZn2+(aq)+2e−⟶Zn(s);E∘=−0.76VCathode half-cell is Ag2O(s)+H2O(l)+2e−⟶2Ag(s)+2OH−(aq)  E∘=0.34VEcell ∘=Ecathode ∘−Eanode ∘        =0.34−(−0.76)        =1.1V