Zinc/silver oxide cell is used in hearing aids and electric watches. The following reactions occur :
`Zn(s) to Zn^(2+)(aq)+2e^(-) , E_(Zn^(2+)//Zn)^(@)=-0.76V`
`Ag_(2)O+H_(2)O+2e^(-) to2Ag+2OH^(-),E_(Ag^(+)//Ag)^(@)=0.344" V"`
Calculate (i) Standard potential of the cell (ii) Standard Gibbs energy.

Explanation

`E_(cell)^(Theta) = E_(("cathode"))^(Theta) - E_(("anode"))^(Theta)`
`E_(cell)^(Theta) = E_((Ag_(2) O|Ag))^(Theta) - E_((Zn^(2+) |Zn))^(Theta)`
`= 0.344 - (- 0.76) = 1.104 V `
Now , `n = 2 ` mol , F = 96500 `mol^(-1) , E_(cell)^(Theta) = 1.104 V`
`therefore " " Delta G^(Theta) = - n F E_(cell)^(Theta)`
`= - (2 mol) xx (96500 C mol^(-1)) xx (1 .104 V)`
`= - 213072 CV " " (1 CV = 1 J)`
`= - 213072 J or -2.13 xx 10^(2) kJ `.