Given reagents `NH_(3), NaOH, HCl`, and `H_(2)S` which one could be used to separated the ions in each of the following mixtures?
a. `Cu^(2+)` and `Zn^(2+)` b. `Cu^(2+)` and `Al^(3+)` c. `Zn^(2+)` and `Al^(3+)`

Explanation

a. `NaOH` in excess [precipitates `Cu(OH)_(2)` but forms soluble `Zn(OH)_(4)^(2-)]` or `H_(2)S` in `HC1` (precipitates `CuS` but not `ZnS)`
b. `NH_(3)` [forming `A1(OH)_(3)(s)` and `Cu(NH_(3))_(4)^(2+) (aq)], naOH` excess [forms `A1(OH)_(4)^(Θ) (aq)` and `Cu(OH)_(2)(s)` , or `H_(2)S +HC1` [forms `CuS` but does not react with `A1^(3+))`
c. `NH_(3)` [forms `A1(OH)_(3)(s)` nad `Zn(NH_(3))_(4)^(2+)(aq)]`