Question

Assertion :Since, solubility of $BaS{O}_4$ in 0.1 M $N{a}_{2}S{O}_4$ is ${10}^{-9}$M, hence its $K_{sp}$ is ${10}^{-18}$. Reason: For $BaS{O}_4$, the value of $K_{sp}=(s{)}^2$ [symbols have their usual meanings].

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is D Assertion is incorrect but Reason is correct

The equilibrium reaction is as shown below.
$BaS{O}_4\left(s\right)\rightleftharpoons \underset{S}{B{a}^{2+}}+\underset{S+0.1}{S{O}_4^{2-}}$
The expression for the solubility product is
$\underset{S<{10}^{-9}}{K_{sp}}=\left[B{a}^{2+}\right]\left[S{O}_4^{2-}\right]=\left(s\right)(s+0.1)$
Hence, $K_{sp}=\left[B{a}^{2+}\right]\left[S{O}_4^{2-}\right]=\left({10}^{-9}\right)\left(0.1\right)={10}^{-10}$.