What is the Ksp for the following equilibrium if zinc phosphate has a molar solubility of 1.53×10−7 M?

Question

What is the Ksp for the following equilibrium if zinc phosphate has a molar solubility of 1.53×10−7 M?

Zn3(PO4)2(s)↽−−⇀3Zn2+(aq)+2PO3−4(aq)

Answer 1

As you did in another question, you wrote PO₃^-4 when it should be PO₄^3-. You must be careful when writing ions and get the subscripts and charges correct. It makes a difference.

Zn₃(PO₄)₂(s) <==> 3Zn²⁺(aq) + 2PO₄^3-(aq)

Ksp = [Zn²⁺]³[PO₄^3-]²

1.53x10^-7 M Zn₃(PO₄)₂ produces 4.59x10^-7 M Zn²⁺ and 3.06x10^-7 M PO₄^3- This can be determined from the stoichiometry of the dissolution equation where 1Zn₃(PO₄)₂ -> 3Zn²⁺ and 2PO₄^3-

Ksp = [4.59x10^-7]³[3.06x10^-7]²

Ksp = 9.1x10^-33