Question

Name the chloride of a metal which is soluble in excess of ammonium hydroxide.

Answer 1

The chloride of a metal that is soluble in excess of ammonium hydroxide is zinc chloride.
On adding ammonium solution, in drops, the colourless solution of zinc chloride forms white gelatinous precipitate of zinc hydroxide. This hydroxide solution dissolves in excess of ammonium hydroxide and forms a complex, colourless tetramine zinc(II) chloride.
ZnCl₂ + NH₄OH → Zn(OH)₂ + 2NH₄Cl
Zn(OH)₂ +2 NH₄Cl + 2 NH₄OH → [Zn(NH₃)₄]Cl₂ + 4 H₂O