Teeth and bones are composed, to a first approximation, of calcium phosphate, Ca3(PO4)2(s). The Ksp for this salt is 1.3 10-32 at 25°C. Calculate the concentration of calcium ion in a saturated solution of Ca3(PO4)2.

Question

Teeth and bones are composed, to a first approximation, of calcium phosphate, Ca3(PO4)2(s). The Ksp for this salt is 1.3  10-32 at 25°C. Calculate the concentration of calcium ion in a saturated solution of Ca3(PO4)2.

Please, help!

DrBob222 · Answer

Let S = solubility of Ca3(PO4)2
.........Ca3(PO4)2 ==> 3Ca^2+ + 2PO4^3-
initial....solid........0.........0
change......S..........+3S.......2S
equil.......S...........3S.......2S

Ksp = (Ca^3+)^3(PO4^3-)^2
Ksp = (3S)^3(2S)^2
Solve for S.