What is the pOH of millimolar solution of $\mathrm{Ca}(\mathrm{OH})_2$ ?

What is the pOH of millimolar solution of $\mathrm{Ca}(\mathrm{OH})_2$ ?
  1. 2.7
  2. 10.3
  3. 12.3
  4. 11.3

Solution

$\begin{aligned} & 1 \mathrm{mM}=10^{-3} \mathrm{M} \\ & \mathrm{Ca}(\mathrm{OH})_2 \longrightarrow \mathrm{Ca}^{2+}+2 \mathrm{OH}^{-} \\ & 10^{-3} \mathrm{M} \\ & \therefore \quad 2 \times 10^{-3} \mathrm{M} \\ & \therefore \quad \mathrm{pOH}=-\log _{10}\left[\mathrm{OH}^{-}\right]=-\log _{10}\left(2 \times 10^{-3}\right)=2.7\end{aligned}$

Asked in: MHT CET 2024 (09 May Shift 1)

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