Equilibrium Ques 73
73. $M Y$ and $N Y_3$, two nearly insoluble salts, have the same $K_{s p}$ values of $6.2 \times 10^{-13}$ at room temperature. Which statement would be true in regard to $\mathrm{MY}$ and $\mathrm{NY}_3$ ?
[2016]
(a) The molar solubilities of $M Y$ and $N Y_3$ in water are identical.
(b) The molar solubility of $M Y$ in water is less than that of $N Y_3$
(c) The salts $\mathrm{MY}$ and $\mathrm{NY}_3$ are more soluble in $0.5 $ $\mathrm{MK}$ than in pure water.
(d) The addition of the salt of $K Y$ to solution of $M Y$ and $N Y_3$ will have no effect on their solubilities.
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Answer:
Correct Answer: 73.(b)
Solution: (b)
$\mathrm{MY} \rightleftharpoons \mid \mathrm{M}^{+}+\mathrm{Y}^{-} $
$ \mathrm{K}_{s p}=\mathrm{s}^2=6.2 \times 10^{-13} $
$ s=\sqrt{6.2^{\prime} 10^{-13}} $
$ s=7.87 \times 10^{-7} \mathrm{~mol} \mathrm{~L}^{-1} $
$ \mathrm{NY}_3 \rightleftharpoons \mid \mathrm{N}^{3+}+3 \mathrm{Y}^{-} $
$ \mathrm{K}_{s p}=s \times(3 s)^3=27 s^4=6.2 \times 10^{-13} $
$ s=\left(\frac{6.2 \times 10^{-13}}{27}\right)^{1 / 4} $
$ s=3.89 \times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1} $
$\therefore$ molar solubility of $\mathrm{NY}_3$ is more than $\mathrm{MY}$ in water.
BETA
