Question

Given that the Ksp value for Ca3(PO4)2 is 8.6×10−19, if the concentration of Ca2+ in solution is 4.9×10−5 M, the concentration of PO3−4 must exceed _____ to generate a precipitate.

Answer 1

.0027 M

Step-by-step explanation:

We must calculate the threshold concentration of PO3−4 using Ksp and the given concentration of Ca2+:

Ca3(PO4)2(s)⇌3Ca2+(aq)+2PO3−4(aq)

Ksp=8.6×10−19=[Ca2+]3[PO3−4]2=(4.9×10−5M)3[PO3−4]2

[PO3−4]=0.0027 M