Question

A solution when diluted with $H_{2}O$ and boiled, it gives a white precipitate. On addition of excess $N{H}_{4}Cl/N{H}_{4}OH$ , the volume of precipitate decreases leaving behind a white gelatinous preciptitate. Identify the precipitate which dissolves in $N{H}_{4}OH/N{H}_{4}Cl$

• A. $Zn(OH{)}_2$
• B. $Al(OH{)}_3$
• C. $Mg(OH{)}_2$
• D. $Ca(OH{)}_2$

Answer 1

The correct option is A $Zn(OH{)}_2$

Due to formation of tetrammine zinc (II) complex: $Z{n}^{+2}+N{H}_{4}OH\to \left[Zn\right(N{H}_3{)}_4{]}^{+2}$