Question

A button cell used in watched funcations as follwing
`Zn(s)+Ag_(2)O(s)+H_(2)O(l)hArr2Ag(s)+Zn^(2+)(aq.)+2OH^(-)(aq)`
If half cell potentials are
`Zn^(2+)(aq.)+2e^(-) rarr Zn(s), E^(@) = -0.76 V`
`Ag_(2)O(s)+H_(2)O(l)+2e^(-) rarr 2Ag(s)+2OH^(-)(aq.),, E^(@) = 0.34V`
The cell potential will be
A. 1.10V
B. 0.42V
C. 0.84V
D. 1.34V

Answer 1

Correct Answer - A
(a) Anode is always the site of oxidation thus, anode half - cell is
`Zn^(2+)(aq)+2e^(-) to Zn(s)," " E^(@)=-0.76 V`
Cathode half-cell is
`Ag_(2)O(s)+H_(2)O(l)+2e^(-) to 2Ag(s)+2OH^(-)(aq), E^(@)=0.34 V`
`E_(cell)^(@)=E_("cathode")^(@)-E_("anode")^(@)`
`=0.34-(-0.76)=+1.10V`