Solubility given Ksp

Question

What is the solubility (in mol/L) of Cu₃PO₄ given that the Ksp is 1.33⋅10^−16

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I'm getting this wrong, not sure if I'm setting it up correctly.

 

Answer 1

Cu₃PO₄(s) <==> 3Cu⁺(aq) + PO₄^3-(aq)

Ksp = [Cu⁺]³[PO₄^2-]

Let x = [PO₄^2-] and the 3x = [Cu⁺]

1.33x10^-16 = (3x)³(x)

27x⁴ = 1.33x10^-16

x⁴ = 4.93x10^-18

x = 4.71x10^-5 M = solubility of Cu₃PO₄