Equilibrium Question 217
Question: What is the minimum concentration of $ SO_4^{2-} $ required to precipitate $ BaSO_4 $ in a solution containing $ 1.0\times {10^{-4}}mol,B{a^{2+}} $ - ( $ K _{sp} $ for $ BaSO_4 $ is $ 4\times {10^{-10}} $ ) [MP PMT 2000]
Options:
A) $ 4\times {10^{-10}}M $
B) $ 2\times {10^{-7}}M $
C) $ 4\times {10^{-6}}M $
D) $ 2\times {10^{-3}}M $
Show Answer
Answer:
Correct Answer: C
Solution:
$ BaSO_4 $ ⇌ $ B{a^{2+}}+SO_4^{2-} $
$ K _{sp}=S^{2}\Rightarrow S=\sqrt{K _{sp}} $ ; $ K _{sp}=[B{a^{2+}}]\times [SO_4^{2-}] $
$ 4\times {10^{-10}}=[1\times {10^{-4}}]\times [SO_4^{2-}] $
$ [SO_4^{2-}]=\frac{4\times {10^{-10}}}{1\times {10^{-4}}}=4\times {10^{-6}} $ .
