Chemical And Ionic Equilibrium Result Question 13
13. Solubility product constant ( $K_{\mathrm{sp}}$ ) of salts of types $M X, M X_2$ and $M_3 X$ at temperature ’ $T$ ’ are $4.0 \times 10^{-8}, 3.2 \times 10^{-14}$ and $2.7 \times 10^{-15}$, respectively. Solubilities ( $\mathrm{mol} $ $\mathrm{dm}^{-3}$ ) of the salts at temperature ’ $T$ ’ are in the order
(2008, 3M)
(a) $M X>M X_2>M_3 X$
(b) $M_3 X>M X_2>M X$
(c) $M X_2>M_3 X>M X$
(d) $M X>M_3 X>M X_2$
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Answer:
Correct Answer: 13. ( d )
Solution:
$\begin{aligned} & M X: \quad K_{\text {sp }}=S^2=4 \times 10^{-8} \\ & \Rightarrow \quad S=2 \times 10^{-4} \\ & M X_2: \quad K_{\text {sp }}=4 S^3=3.2 \times 10^{-14} \quad \Rightarrow S=2 \times 10^{-5} \\ & M_3 X: \quad K_{\text {sp }}=27 S^4=2.7 \times 10^{-15} \Rightarrow S=10^{-4} \\ \end{aligned}$
Order of solubility is $ M X > M_3 X > M X_2 $
BETA
