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6-2.Equilibrium-II (Ionic Equilibrium)
hard
The ${K_{sp}}$ of $Mg{(OH)_2}$ is $1 \times {10^{ - 12}},\,0.01\,M\,Mg{(OH)_2}$ will precipitate at the limiting $pH$
A
$3$
B
$9$
C
$5$
D
$8$
Solution
(b) $Mg{(OH)_2}$ $ \rightleftharpoons $ $M{g^{2 + }} + 2O{H^ – }$
${K_{sp}} = [M{g^{2 + }}]{[O{H^ – }]^2}$
$1 \times {10^{ – 12}} = 0.01\,{[O{H^ – }]^2}$
${[O{H^ – }]^2} = 1 \times {10^{ – 10}}$ $ \Rightarrow [O{H^ – }] = {10^{ – 5}}$
$[{H^ + }] = {10^{ – 14}}/{10^{ – 5}} = {10^9}$
$pH = – \log [{H^ + }] = – \log [{10^{ – 9}}] = 9$
Standard 11
Chemistry