Question

State your observations when ammonium hydroxide solution is added drop by drop and then in excess to the following solution:

Zinc sulphate solution

Answer 1

When NH₄OH is added to a zinc sulphate solution dropwise, a white, gelatinous ppt. is obtained.

\[\ce{\underset{(Colourless solution)}{ZnSO4} + 2NH4OH -> \underset{(White, gelatinous ppt)}{Zn(OH)2\downarrow} + (NH4)2SO4}\]

With the excess of NH₄OH, the ppt. dissolves to give a colourless solution of tetraamine zinc(II)sulphate.

\[\ce{\underset{(Zinc hydroxide)}{Zn(OH)2} + (NH4)2SO4 + \underset{(Excess)}{2NH4OH} -> \underset{(Colourless solution)}{\underset{Tetrammine zinc (II)}{[Zn(NH3)4]SO4}} + 4H2O}\]