ElectrochemistryMedium
Question
A button cell used in watches function as following
Zn(s) + Ag2O(s) + H2O(l) ⇋ 2Ag(s) + Zn2+(aq) + 2OH-(aq)
If half cell potentials are
Zn2+(aq) + 2e- → Zn(s) ; Eo = -0.76V
Ag2O(s) + H2O(l) + 2e- → 2Ag(s) + 2OH-(aq) ; Eo = 0.34V
The cell potential will be :-
Zn(s) + Ag2O(s) + H2O(l) ⇋ 2Ag(s) + Zn2+(aq) + 2OH-(aq)
If half cell potentials are
Zn2+(aq) + 2e- → Zn(s) ; Eo = -0.76V
Ag2O(s) + H2O(l) + 2e- → 2Ag(s) + 2OH-(aq) ; Eo = 0.34V
The cell potential will be :-
Options
A.1.34 V
B.1.10 V
C.0.42 V
D.0.84 V
Solution
Zn2+(aq) + 2e- → Zn(s) ; Eo = -0.76 V;
Ag2O(s) + H2O(l) + 2e- → 2Ag(s) + 2OH(aq) ; Eo = 0.34 V
Zn(s) + Ag2O(s) + H2O(l) → 2Ag(s) + Zn+2(aq) + 2OH-(aq) ; Ecell = ?
Eocell = (EoR.P.)cathode - (EoR.P.)anode
Eocell = 0.34 - (-0.76) = 1.10 V
Ecell = Eocell = 1.10V
Ag2O(s) + H2O(l) + 2e- → 2Ag(s) + 2OH(aq) ; Eo = 0.34 V
Zn(s) + Ag2O(s) + H2O(l) → 2Ag(s) + Zn+2(aq) + 2OH-(aq) ; Ecell = ?
Eocell = (EoR.P.)cathode - (EoR.P.)anode
Eocell = 0.34 - (-0.76) = 1.10 V
Ecell = Eocell = 1.10V
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