The equilibrium `Cu^(+2)(aq)+Cu(s) hArr2Cu^(+)` established at `20^(@)C` corresponds to `([Cu^(+2)])/([Cu^(+)])=2.02xx10^(4+)`. The standard potential . `E_(Cu^(+2).Cu)^(0)=0.33` volt at this temperature . What is the standard potential `E_(Cu//Cu^(+))^(0)`?

Options

A. `-0.457`
B. `-0.125V`
C. `-0.66V`
D. `-0.250V`

Answer

A

Explanation

At equilibirum
`E_(1)^(0)=+(0.0591)/(1)log_(10)(([Cu^(+)]^(2))/([Cu^(++)]))`
`=(0.0591)/(1)log((10^(-4))/(2.02))=-0.254`
`E_(1)^(0)i=E_(Cu^(2+)//Cu^(+))^(0)-E_(Cu^(+)//Cu)^(0)`
and `E_(Cu^(+2)//Cu)^(0)==(E_(Cu^(+2)//Cu^(+))^(0)+E_(Cu^(+)//Cu)^(0))/(2)`
so `E_(1)^(0)=2E_(cu^(+2)//Cu)^(0)-2E_(Cu^(+)//Cu)^(0)`
`E_(Cu^(+)//Cu)^(0)=0.457`
`E_(Cu//Cu^(+))^(0)=-0.457`