Find number of basic radicals among the following cations, which can form soluble complex on adding excess of NH3 solution : Cd2+(aq.), Pb2+(aq.), Ni2+(aq.), Mn2+(aq.), Zn2+(aq.), Ag+(aq.), Hg2+(aq.),

Question

Find number of basic radicals among the following cations, which can form soluble complex on adding excess of NH3 solution : Cd2+(aq.), Pb2+(aq.), Ni2+(aq.), Mn2+(aq.), Zn2+(aq.), Ag+(aq.), Hg2+(aq.), Fe3+(aq.), Mg2+(aq.)

Prashant Kotian · Accepted Answer

Correct answer: 4. Step 1: When NaOH is added to the mixture containing Al3+, Zn2+, and Cu2+, all of them initially form hydroxide precipitates. Step 2: Since Al(OH)3 and Zn(OH)2 are amphoteric, they dissolve in excess NaOH to form soluble aluminate ([Al(OH)4]-) and zincate ([Zn(OH)4]2-) complexes. Step 3: In contrast, Cu(OH)2 is a basic hydroxide and remains insoluble as a characteristic blue precipitate, allowing both the identification and separation of Cu2+ in one step, matching option (c).

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