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}} $ .



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