Ionic Equilibrium Question 5
Question 5 - 2024 (30 Jan Shift 1)
The $pH$ at which $Mg(OH) _2\left[K _{sp}=1 \times 10^{-11}\right]$ begins to precipitate from a solution containing $0.10 M Mg^{2+}$ ions is _________.
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Answer (9)
Solution
recipitation when $Q _{sp}=K _{sp}$
$\left[Mg^{2+}\right]\left[OH^{-}\right]^{2}=10^{-11}$
$0.1 \times\left[OH^{-}\right]^{2}=10^{-11} \Rightarrow\left[OH^{-}\right]=10^{-5}$
$\Rightarrow pOH=5 \Rightarrow pH=9$
