Question

Ba3(PO4)2 has a Ksp of 3.2x10-23. What is the concentration of Ba2+ ions in a saturated solution of barium phosphate?

Answer 1

.....................Ba3(PO4)2.................3Ba^2+(aq)...............2[PO4]^3-(aq)
initial...............solid................................0............................0
change..........solid-x...............................3x..........................2x
equilibrium....all solid..............................3x..........................2x

Ksp = (Ba^2+)^3*[(PO4)^3-]^2 = 3.2E-23 = (3x)^3*(2x)^2
Solve for x = (Ba^2+) and multiply by 3 for (Ba^2+) aq a saturated solution of Ba3(PO4)2