CaF₂ এর জলীয় দ্রবণে ফ্লোরাইড আয়নের গাড়ত্ব 0.0076g/L হলে CaF₂ এর দ্রাব্যতা গুণাঙ্ক কত? 

$\begin{aligned} 2\left[F^{-}\right]=2 S & =0.0076 \mathrm{gL}^{-1} \\ \therefore S & =0.0038 \mathrm{gL}^{-1} \\ & =\frac{0.0038}{19} \mathrm{molL}^{-1} \\ & =0.0002 \mathrm{molL}^{-1}\end{aligned}$

$\mathrm{CaF}_{2} \rightleftharpoons \mathrm{Ca}^{2+}(\mathrm{aq})+2 \mathrm{~F}^{-}(\mathrm{aq})$

ধরি,

$\left[\mathrm{Ca}^{2+}\right]=\left[\mathrm{F}^{-}\right]=s$

We know,

$\begin{aligned} K_{s p} & =\left[\mathrm{Ca}^{2+}\right] \times\left[2 \mathrm{~F}^{-}\right]^{2} \\ & =s \times(2 \mathrm{~s})^{2} \\ & =4 s^{3} \\ & =4 \times(0.0002)^{3} \\ & =3.2 \times 10^{-11} \end{aligned}$