Question

The solubility product of salt $B_{2}A$ is $3.2\times10^{-11}$ at 298 K. What is solubility of the salt at same temperature?

• A. $5.52\times10^{-5}moldm^{-3}$
• B. $4.92\times10^{-4}moldm^{-3}$
• C. $2.00\times10^{-4}moldm^{-3}$
• D. $3.52\times10^{-5}moldm^{-3}$

Hint:

For $X_2Y$ or $XY_2$ type salts, $K_{sp} = 4s^3$.

Answer 1

The Correct Option is C

Step 1: Concept
For a salt $B_2A$, the dissociation is $B_2A \rightleftharpoons 2B^+ + A^{2-}$.

Step 2: Formula
$K_{sp} = (2s)^2 \times (s) = 4s^3$

Step 3: Analysis
- $3.2 \times 10^{-11} = 4s^3$
- $s^3 = 0.8 \times 10^{-11} = 8 \times 10^{-12}$
- $s = \sqrt[3]{8 \times 10^{-12}} = 2 \times 10^{-4}$

Step 4: Conclusion
Hence, correct answer is (C). Final Answer: (C)