For which sparingly soluble salt is the relationship between $K_{sp}$ and $S$ (solubility) given by $S = (K_{sp} / 4)^{1/3}$?

If the $pH$ of a $0.001 \, M \, Mg(NO_3)_2$ solution is $9$,will precipitation occur? Given the $K_{sp}$ of $Mg(OH)_2 = 8.9 \times 10^{-12}$.

Which of the following happens when $NH_{4}OH$ is added gradually to the solution containing $1 \ M \ A^{2+}$ and $1 \ M \ B^{3+}$ ions?
Given: $K_{sp}[A(OH)_{2}] = 9 \times 10^{-10}$ and $K_{sp}[B(OH)_{3}] = 27 \times 10^{-18}$ at $298 \ K$.

$A_{3}B_{2}$ is a sparingly soluble salt of molar mass $M \ g \ mol^{-1}$ and solubility $x \ g \ L^{-1}$. The solubility product satisfies $K_{sp} = a(\frac{x}{M})^{5}$. The value of $a$ is ...... . (Integer answer)

The correct representation for the solubility product of $SnS_2$ is:

If $S$ and $K_{sp}$ are respectively solubility and solubility product of a sparingly soluble binary electrolyte,then