Question

what is the solubility in mol/L of insoluble Ca3(PO4)2 (Ksp=1.00x10^-26)in a solution containing .00100 M Na3PO4?
a. 2.15x10^-7
b. 7.18x10^-8
c. 7.18x10^-9
d. 1.00x10^-23
e. answer not given

Answer 1

x = solubility Ca3(PO4)2.
Ca3(PO4)2 ==> 3Ca^2+ + 2PO4^3-
.....x..........3x.......2x

............Na3PO4 --> 3Na^+ + PO4^3-
initial......001M.........0......0
change......-0.001.....0.001....0.001
equil........0.........0.001....0.001

Ksp = (Ca^2+)^3(PO4)^2
Substitute and solve for x.
For Ca^2+ you substitute 2x
For PO4^3- you substitute 3x+0.001 (that's 3x from the Ca3(PO4)2 and 0.001 from the Na3PO4.

Answer 2

2.15*10^-8

Answer 3

answer