Question

the solubility of strontium arsenate, Sr3(AsO4)2, is 0.0560 g/L. What is the Ksp?

Answer 1

First, i would find the concentration of Sr3(AsO4)2 in mole per liter. Let's label it S.

then, i would write out the solubility equilibrium:

Sr3(AsO4)2 <--> 3 Sr^p+ + 2 AsO4^m-

i will let you find out p and m but we actually don't need to know them.

according to the law of equilibrium: Ksp = [Sr^p+] ^3 [AsO4^m-] ^2

From the value of S, we can infer the equilibrium concentrations of the two ions. plugging in these values, we get the Ksp.