If the molar solubility of CaF2 at 35 C is 1.24103 mol/L, what is Ksp at this temperature?

1 Answer
Jun 9, 2016

Ksp = [Ca2+][F]2 = ??

Explanation:

Ksp, the solubility product derives from the solubility expression:

CaF2(s)Ca2++2F

And Keq = [Ca2+][F]2[CaF2(s)]

However, [CaF2(s)], the concentration of a solid is a meaningless quantity.

Thus: Keq = Ksp = [Ca2+][F]2

Given this expression, we simply fill in the blanks:

Ksp = (1.24×103)(2×1.24×103)2

= 4×(1.24×103)3

= ???

The given Ksp is calculated for 35 C. At lower temperature, would you expect Ksp to increase or decrease? Give a reason for your answer.