Question

I had 2,3,5,4,1 but it was wrong.

Rank the following five salts in order of decreasing solubility, in terms of mass per unit volume.  
(The most soluble gets rank 1, the least soluble gets rank 5.)

1 2 3 4 5  Ag₃PO₄     (K_sp = 1.80×10^-18)
1 2 3 4 5  Ag₂CO₃     (K_sp = 8.10×10^-12)
1 2 3 4 5  Ca₅(PO₄)₃OH     (K_sp = 6.80×10^-37)
1 2 3 4 5  Sr₃(PO₄)₂     (K_sp = 1.00×10^-31)
1 2 3 4 5  AgCl     (K_sp = 1.60×10^-10)

Answer 1

Ag3PO4 ---> 3Ag+ + PO43-
3s s

Ksp = (3s)^3 * s
1.80*10^-18 = 27*s^4
s = 1.61*10^-5 mol/L
molar mass of Ag3PO4 = 418.6 g/mol
solubility = 1.61*10^-5 * 418.6 = 6.72*10^-3 g/L

Ag2CO3 --> 2Ag+ + CO32-
2s s
Ksp = (2s)^2 *s
8.10*10^-12 = 4*s^3
s = 1.26*10^-4 mol/L

molar mass of Ag2CO3 = 275.7 g/mol

solubility = 1.26*10^-4 * 275.7 = 3.49*10^-2 g/L

Ca5(PO4)3OH ---> 5Ca2+ + PO43- + OH-

Ksp = (5s)^5 *s*s
6.80*10^-37 = 3125*s^7
s^7 = 2.176*10^-40
s = 2.16*10^-6 mol/L
Molar mass of Ca5(PO4)3OH = 502 g/mol
solubiliyty = 2.16*10^-6 * 502= 1.08*10^-3 g/L

for Sr3(PO4)2
ksp = (3s)^3*(2s)^2
1*10^-31 = 108*s^5
s^5 = 9.26*10^-34
s = 2.47*10^-7 mol/L
= 2.47*10^-7*453
= 1.12*10^-4 g/L

for AgCl:
Ksp = s^2
1.6*10^-10
s = 1.26*10^-5 mol/L
= 1.26*10^-5 * 143
=1.81*10^-3 g/L

1---> Ag2CO3
2--> Ag3PO4
3---> AgCl
4--->Ca5(PO4)3OH   
5---> Sr3(PO4)2