A solution is prepared by adding some solid CaF2 to water and allowing the solid to come to equilibrium with the solution. The equilibrium constant for the reaction below is Kc = 3.9x10-11.
CaF2(s) → Ca2+(aq) + 2 F -(aq)
What is the equilibrium concentration of Ca2+ in the solution? Assume some of the solid is still present.