Copper can be extracted by hydrometallurgy but not zinc.
Explanation : `rarr E^(0)` value of `Zn^(+2)//Zn= -0.762V` is less than that of `E^(0)` value of `Cu^(+2)//Cu=0.337V.`
`rarr` from the above data zinc is a stronger reducing agent and can easily displace the `Cu^(+2)`ions present in the complex.
`underset(" Soluble complex")([Cu(CN)_(2)])+Znrarr([Zn(CN)_(2)])+underset("precipitate")(Cu)`
Zinc can be isolated by hydrometallurgy only when stronger reducing agents than zinc are present.
So zinc cannot be extracted by hydrometallurgy.
