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

Options

A. 1.10V
B. 0.42V
C. 0.84V
D. 1.3V

Answer

A

Explanation

For hy drogen electrode , reduction reaction is
`H^(+)+e=(1)/(2)H_(2)`
`E_(H^(+)//(1)/(2)H_(2))^(@)=E_(H^(+)//(1)/(2)H_(2))^(@)-(0.059)/(n)"log"(p^(1//2)H_(2))/([H^(+)])`
`=0-(0.059)/(n)"log"(1)/(10^(-10))=0.0591`
[pH=10means `|H^(+)| =10^(-1)M`]
`therefore` Oxidation potential `=0.591V`.