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