A _ 3 B _ 2 is a sparingly soluble salt of molar mass M(g mol ^ - 1...

Solubility =\left(\dfrac{x}{m}\right)$mole/lit<br />${A}_{3}{B}_{2}\left(s\right)\mathop{⇌ 3{A}^{2 +}}_{\dfrac{3x}{M}}\mathop{( aqs ) + 2{B}^{3 -} ( aqs )}_{2\left(\dfrac{x}{M}\right)}$<br />${K}_{sp} = {\left(\dfrac{3x}{M}\right)}^{3}{\left(\dfrac{2x}{M}\right)}^{2}$<br />$= \left(3\right){}^{3}{\left(2\right)}^{2}{\left(\dfrac{x}{m}\right)}^{5}$<br />$= 27 \times 4{\left(\dfrac{x}{m}\right)}^{5}$<br />$= 108{\left(\dfrac{x}{m}\right)}^{5} = a{\left(\dfrac{x}{M}\right)}^{5}$<br />So$a = 108