Question

What is the equilibrium expression for the dissolution of $C{a}_3(P{O}_4{)}_2$ where the above is true?

• A. $K_{sp}=\left[C{a}^{2+}{]}^3\right[P{O}_4^{3-}{]}^2$
• B. $K_{sp}=\left[C{a}^{2+}{]}^2\right[P{O}_4^{3-}{]}^3$
• C. $K_{sp}=\left[C{a}^{2+}\right]\left[P{O}_4^{3-}\right]/\left[C{a}_3\right(P{O}_4{)}_2]$
• D. $K_{sp}=\left[C{a}^{2+}{]}^3\right[P{O}_4^{3-}{]}^2/\left[C{a}_3\right(P{O}_4{)}_2]$
• E. $K_{sp}=\left[C{a}^{2+}{]}^2\right[P{O}_4^{3-}{]}^3/\left[C{a}_3\right(P{O}_4{)}_2]$

Answer 1

The correct option is A $K_{sp}=\left[C{a}^{2+}{]}^3\right[P{O}_4^{3-}{]}^2$

$C{a}_3(P{O}_4{)}_2$ can be dissociated as:

$C{a}_3(P{O}_4{)}_2$ $\to$ $3C{a}^{2+}$ $+$ $2P{O}_4^{3-}$

Solubility product $K_{sp}$ of a salt can be expressed as the product of the concentration of the ions of the salt, with each concentration term raised to the power equal to the co-efficient of that ion in the balanced equation.

Thus in this case-

$K_{sp}$$=$$[C{a}^{2+}{]}^3$$[P{O}_4^{3-}{]}^2$

Thus, option $A$ is the correct answer.