Estimate the standard reduction potential for the copper `//` copper sulphide electrode. For `CuS,K_(sp)=8.5 xx 10^(-36),E^(c-)._(Cu|Cu^(2+))=-0.34V.`

Explanation

`E^(c-)._(CuS|Cu)=x`
`E^(c-)._(Cu|Cu^(2+))=-0.34V`
`E^(c-)._(cell)=x-0.34V`

Cell is in equilibrium
`:. E_(cell)=0`
`:. E_(cell)=E^(c-)._(cell)-(0.059)/(2)log[Cu^(2+)][S^(2-)]`
`E^(c-)._(cell)=(0.059)/(2)log K_(sp)`
`=(0.059)/(2)log(8.5xx10^(-36))=01.04V`
Since `E^(c-)._(cell)=x-0.34`
`:. x=-.34=-1.04Vimplies x=-0.70V`
`:. E^(c-)._(CuS|Cu)=-0.70V`
or standard reduction potential for `Cu|CuS=-0.70V.`