Solubility problem?

Question

Calculate the solubility of each of the following compounds in moles per liter. Ignore any acid-base properties.

(a) Ag3PO4, Ksp = 1.8 10-18

(b) CaCO3, Ksp = 8.7 10-9

(c) Hg2Cl2, Ksp = 1.1 10-18 (Hg22+ is the cation in solution.)

Answer 1

.. .. .. .. .. Ag3PO4 <=> 3Ag+ + PO4(-3)
Dissolve .. .. s
produce .. .. .. .. .. .. .. .. .. 3s .. .. .. s
At equil .. .. .. .. .. .. .. .. .. .. 3s .. .. .. s

Ksp = [Ag+]^3[PO4(-3)] =(3s)^3*s= 27s^4 =>
s=(Kps/27)^(1/4) = ( (1.8*10^-18)/27 )^(1/4) =1.61*10^-5

You can do similarly the others