Question

A solution when diluted with $H_2 0$ and boiled, it gives a white precipitate. On addition of excess $NH_4 CI / NH_4 0H$, the volume of precipitate decreases leaving behind a white gelatinous precipitate. Identify the precipitate which dissolves in $NH_4 OH / NH_4 CI.$

• A. $Zn(OH)_2$
• B. $AI(OH)_3$
• C. $Mg(OH)_2$
• D. $Ca(OH)_2$

Answer 1

Answer: (A)

$Zn(OH)_2$

Answer 2

$Zn^{2+} + 2H_2 O \longrightarrow \underset{White}{Zn(OH)_2 \downarrow} + 2H^+$