Chemical And Ionic Equilibrium Result Question 56
56. The solubility of $\mathrm{Pb}(\mathrm{OH})_2$ in water is $6.7 \times 10^{-6} \mathrm{M}$. Calculate the solubility of $\mathrm{Pb}(\mathrm{OH})_2$ in a buffer solution of $\mathrm{pH}=8$.
(1999, 4M)
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Answer:
Correct Answer: 56. ( $1.2 \times 10^{-3} $ M )
Solution:
- In water,
$ \begin{aligned} K_{\text {sp }} & =4 S^3=4\left(6.7 \times 10^{-6}\right)^3 \\ & =1.2 \times 10^{-15} \end{aligned} $
In buffer of $\mathrm{pH}=8, \mathrm{pOH}=6,\left[\mathrm{OH}^{-}\right]=10^{-6}$
$ \begin{aligned} K_{\text {sp }} & =S\left[\mathrm{OH}^{-}\right]^2 \\ S & =\frac{1.2 \times 10^{-15}}{10^{-12}}=1.2 \times 10^{-3} \mathrm{M} \end{aligned} $
BETA
