Question

$K_{sp}$ value of ${Al\left(OH\right)}_3$ and ${Zn\left(OH\right)}_2$ are 8.5 $\times$ ${10}^{-23}$ and 1.8 $\times$ ${10}^{-14}$ respectively. If ${NH}_{4}OH$ is added in a solution of ${Al}^{+3}$ and ${Zn}^{+2}$ which will precipitate earlier:

• A. ${Al\left(OH\right)}_3$
• B. ${Zn\left(OH\right)}_2$
• C. Both together
• D. None will precipitate

Answer 1

The correct option is A ${Al\left(OH\right)}_3$

$K_{sp}$ of $Al(OH{)}_3=8.5\times {10}^{-23}$

$K_{sp}$ of $Zn(OH{)}_2=1.8\times {10}^{-14}$

After adding of $N{H}_{4}OH$ in the solution of $A{l}^{+3}$ and $Z{n}^{+2}$, $Al(OH{)}_3$ will precipitatet earlier because its solubility product value is less then $Zn(OH{)}_2$.