Question

The solubility of $Al\left(O{H}_3\right)$ in a buffer solution at $pH=8.0$ is:

$[Ksp$ of $Al(OH{)}_3=2.7\times {10}^{-27}]$

• A. ${10}^{-7}M$
• B. $2.7\times {10}^{-9}M$
• C. $2.7\times {10}^{-6}M$
• D. $2.7\times {10}^{-3}M$

Answer 1

The correct option is A ${10}^{-7}M$

$Al{\left(OH\right)}_3\rightleftharpoons {Al}^{3+}+3{OH}^{-}$

$S$ $3X$

$K_{sp}=\left(S\right){\left(3X\right)}^3$

$=27\left(S\right){\left(X\right)}^3$

Given $p^H=8\Rightarrow p^{OH}=6\Rightarrow \left[{OH}^{-}\right]={10}^{-6}$

$\Rightarrow X={10}^{-6}$

Given, $K_{sp}=2.7\times {10}^{-27}$

$\Rightarrow 2.7\times {10}^{-27}=27\left(S\right){\left({10}^{-6}\right)}^3$

$S={10}^{-7}M$

$\Rightarrow$ Solubility $={10}^{-7}M$

Ans :- A