Cations are classified into varius groupon the basis oftheir behaviour againstsomereagents .The groupreagentused for the classifactionof most common cationare HCI,H_(2)S,NH_(4)OH,(NH_(4))_(2)CO_(3). Classification is based on whether a cationreacts withthese reagents by theformationof precipitates ornot . Which one amongthe following paires of ions cannot beseparated by H_(2)S in the presenceofdilute hydrochloric acid ?

Cations are classified into varius groupon the basis oftheir behaviour

1.	Cations are classified into varius groupon the basis oftheir behaviour againstsomereagents .The groupreagentused for the classifactionof most common cationare HCI,H_(2)S,NH_(4)OH,(NH_(4))_(2)CO_(3). Classification is based on whether a cationreacts withthese reagents by theformationof precipitates ornot . Which one amongthe following paires of ions cannot beseparated by H_(2)S in the presenceofdilute hydrochloric acid ?
Answer» `Bi^(2+),CD^(2+)` `AI^(2+),Hg^(2+)` `ZN^(3+),Cu^(2+)` `Ni^(2+),Cu^(2+)` Solution :Both `Bi^(3+) and Cd^(2+)` will be precipitate in `Bi_(2)S_(3)` (black) and `CdS` (YELLOW) by `H_(2)S` as both low VALUES of `K_(sp)` than `AI^(3+),Zn^(2+) and Ni^(2+)` (as SULPHIDES)