- Home
- Standard 11
- Chemistry
6-2.Equilibrium-II (Ionic Equilibrium)
hard
At $25\,^oC$, the solubility product of $Mg(OH)_2$ is $1.0\times10^{-11}$. At which $pH$, will $Mg^{2+}$ ions start precipitating in the form of $Mg(OH)_2$ from a solution of $0.001\, M\, Mg^{2+}$ ions?
A
$9$
B
$10$
C
$11$
D
$8$
(AIIMS-2017)
Solution
$Mg{(OH)_2} \leftrightarrow M{g^{ +2}} + 2O{H^ – }$
${K_{sp}} = [M{g^{ + 2 }}]{[O{H^ – }]^2}$
$1.0 \times {10^{ – 11}} = {10^{ – 3}} \times {[O{H^ – }]^2}$
$[O{H^ – }] = \sqrt {\frac{{{{10}^{ – 11}}}}{{{{10}^{ – 3}}}}} = {10^{ – 4}}$
$\therefore \,pOH = 4$
$\therefore pH + pOH = 14$
$\therefore \,pH = 10$
Standard 11
Chemistry