Question

Solubility product constant ( $K_{sp}$ )of salts of types $ MX_1, MX_ 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 }$, respectively. Solubilities (mol dm$^{- 3}$ ) of the salts at temperature $T$" are in the order

• A. $MX > MX_2 > M_3 X $
• B. $M_3X > MX_2 > MX $
• C. $ MX_2 > M_3 X > MX $
• D. $MX > M_3 X > MX_2 $

Answer 1

Answer: (D)

MX : $ K_{ s p } = S^2 = 4 \times 10^{ - 8 } $
$\Rightarrow S = 2 \times 10^{ - 4 } $
$ MX_2 : K_{ s p } = 4 \, S^3 = 3.2 \times 10^{ - 14 } \Rightarrow S = 2 \times 10^{ - 5 } $
$ M_3 \, X : K_{ sp } = 27 S^4 = 2.7 \times 10^{ - 15 } \Rightarrow S = 10^{ - 4 } $
Order of solubility is $MX > M_3 X > MX_2 $