Equilibrium Question 230
Question: What is the solubility of calcium fluoride in a saturated solution, if its solubility product is $ 3.2\times {10^{-11}} $ [CPMT 1997]
Options:
A) $ 2.0\times {10^{-4}},mole/litre $
B) $ 12.0\times {10^{-3}},mole/litre $
C) $ 0.2\times {10^{-4}},mole/litre $
D) $ 2\times {10^{-3}},mole/litre $
Show Answer
Answer:
Correct Answer: A
Solution:
$ \underset{S}{\mathop{CaF_2}}, $ ⇌ $ \underset{S,}{\mathop{C{a^{++}}}},+\underset{{{(2S)}^{2,}}}{\mathop{2{F^{-}}}}, $
$ K _{sp}=4S^{3} $
$ S=\sqrt[3]{\frac{K _{sp}}{4}} $
$ =\sqrt[3]{\frac{3.2\times {10^{-11}}}{4}} $
$ =2\times {10^{-4}} $ m/l.
