Which one among the following pairs of ions cannot be separated by `H_(2)S` in dilute hydrochloric acid ?

Options

A. `Bi^(3+) , Sn^(4+)`
B. `Al^(3+) , Hg^(2+)`
C. `Zn^(2+) , Cu^(2+)`
D. `Ni^(2+) , Cu^(2+)`

Answer

A

Explanation

Both belong to same group i.e. `II^(nd)` group and their `K_(SP)` values are low, so both are precipitated according to the following reactions.
`{:(2Bi^(3+),+,3S^(2-),to,Bi_(2)S_(3),darr,("black")),(Sn^(4+),+,2S^(2-),to,SnS_(2),darr,("yellow")):}`