The standard reduction potential `E^(@)(Bi^(3+)//Bi)` and `E^(@)(Cu^(2+)//Cu)` are `0.226V` and `0.344V` respectively. A mixture of salts of bismuth and copper at unit concentration each is electrolysed at `25^(@)C`. To what value can `[Cu^(2+)]` be brought down before bismuth starts to deposit in electrolysis.

Answer

`[Cu^(2+)] = 10^(-4)M`

Explanation

`E_(Cu^(2+)//Cu) = E_(Cu^(2+)//Cu)^(@) +(0.059)/(2) lg c[Cu^(2+)]`
`[Cu^(2+)] = 10^(-4)m`