Question

The solubility $C{a}_3{(P{O}_4)}_2$ is s mole. What is the solubility product of $C{a}_3{(P{O}_4)}_2$ ?

• A. $8s^3$
• B. $9s^2$
• C. $108s^5$
• D. $72s^2$

Answer 1

Answer: (C)

$\underset{\begin{array}{c}\text{s mole litr}{\text{e}}^{-1}\\ \text{(soluble)}\end{array}}{a_3{(P{O}_4)}_2}\to \underset{\begin{array}{c}\text{3s mole}\\ \text{litr}{\text{e}}^{-1}\end{array}}{3C{a}^{2+}}+\underset{\begin{array}{c}\text{2s mole}\\ \text{litr}{\text{e}}^{-1}\end{array}}{2P{O_4}^{3-}}$ $K_{sp}$ of $C{a}_3{(P{O}_4)}_2=3{[C{a}^{++}]}^3+{[P{O_4}^{3-}]}^2$ $={(3s)}^3\times {(2s)}^2$ $=27s^3\times 4s^2=108s^5$