Question

What is the solubility of $Al(OH{)}_3,(K_{sp}=1\times {10}^{-33})$ in a buffer solution of $pH=4$ ?

• A. ${10}^{-3}M$
• B. ${10}^{-6}M$
• C. ${10}^{-4}M$
• D. ${10}^{-10}M$

Answer 1

The correct option is A ${10}^{-3}M$

$pH=4\Rightarrow \left[H^{+}\right]={10}^{-4}M\Rightarrow \left[O{H}^{-}\right]={10}^{-10}M$
$Al(OH{)}_3\rightleftharpoons A{l}^{+3}+3O{H}^{-}$
$K_{sp}\left(Al\right(OH{)}_3)=S\times S^3$
$K_{sp}\left(Al\right(OH{)}_3)=[A{l}^{+3}\left]\right[O{H}^{-}{]}^3$
$\left[A{l}^{3+}\right][O{H}^{-}{]}_3=1\times {10}^{-33}$
$\left[A{l}^{3+}\right]({10}^{-10}{)}^3=1\times {10}^{-33}\Rightarrow [A{l}^{+3}]={10}^{-3}M$