a Ksp question, equilibria?

Question

Using the following data calculate the Ksp value for each solid.
(a) The solubility of Pb3(PO4)2 is 6.2 10-12 mol/L.

(b) The solubility of Li2CO3 is 7.4 10-2 mol/L.

Answer 1

Imagine you have the salt of the general formula AxBy and s is its molar solubility

.. .. .. .. .. AxBy <=> xA(+y) + yB(-x)
Dissolve .. s
Produce .. .. .. .. .. .. xs .. .. .. .. ys

Ksp=[A+y]^x [B-x]^y = (xs)^x* (ys)^y = (x^x)*(y^y)* s^(x+y)

For Pb3(PO4)2, x=3, y=2, s=6.2*10^-12 mol/L
For Li2CO3, x=2, y=1, s=7.4*10^-2 mol/L

You can do the math and calculate the Ksp in each case.