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. `0.42 V`
B. `0.84 V`
C. `1.34 V`
D. `1.10 V`

Answer

D

Explanation

If both the half cell potentials arc standard reduction potentials, then standard electromotive force of the cell is given as
`E_("cell")^(@) = E_(R)^(ɵ)-E_(L)^(ɵ)`
or `E_("cell")^(@) = E_("cathode")^(ɵ)-E_("anode")^(ɵ)`
Half cell having the higher reduction potential serves the role of cathode. Thus
`E_("cell")^(@) = (0.34 V)-(-0.76 V)`
`= 1.1 V`