Which of the following mixtures cann be separated by using excess `NH_(3) ` solution?

Options

A. `Bi_((aq.))^(3+) and Al_((aq.))^(3+)`
B. `Al_((aq.))^(3+) and Zn_((aq.))^(2+)`
C. `Hg_((aq.))^(2+) and Pb_((aq.))^(2+)`
D. `Cu_((aq.))^(2+) and Cd_((aq.))^(2+)`

Answer

B

Explanation

`Al^(3+) and Zn^(2+)` both from white ppt. with `NH_(3)` solution but white ppt. of `Zn(OH)_(2)` is soluble in excess of
`NH_(3)`.
`Al^(3+)+3NH_(3)+3H_(2)O to Al(OH)_(3) darr overset("Ex. "NH_(3)" solution")to` No reaction
`Zn^(2+)+2NH_(3)+2H_(2)O to Zn(OH)_(2) darr overset("Ex. "NH_(2) " solution")to[Zn(NH_(3))_(4)]^(2+)`