Question

The solubility of a saturated solution of calcium fluoride is $2\times {10}^{-4}$ moles per litre Its solubility product is:

• A. $22\times {10}^{-11}$
• B. $14\times {10}^{-4}$
• C. $2\times {10}^{-2}$
• D. $32\times {10}^{-12}$

Answer 1

Answer: (D)

$32\times {10}^{-12}$

The solubility $\left(s\right)$ of saturated solution of ${CaF}_2$ is $2\times {10}^{-4}M.$

$\underset{S}{{CaF}_2}\rightleftharpoons \underset{S}{{Ca}^{2+}}+\underset{2S}{{2F}^{-}}$

$\therefore$ Solubility product, $K_{sp}=\left[{Ca}^{2+}\right]{\left[F^{-}\right]}^2$

$=S.{\left(2S\right)}^2={4S}^3$

$=4\times {(2\times {10}^{-4})}^3$

$=32\times {10}^{-12}$

$\therefore$ Correct answer is D.