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 precipitate. 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 $(OH{)}_2$

$Zn(OH{)}_2$ forms white precipitate when its solution is diluted with $H_{2}O$ and boiled. This precipitate dissolves on addition of excess $N{H}_{4}Cl/N{H}_{4}OH$. The volume of precipitate decreases and forms the gelatinous precipitate of $\left[Zn\right(N{H}_3{)}_4]C{l}_2$ - Tetraaminezinc(II) chloride complex.