Solid calcium fluoride, CaF₂, is added to water at 25°C. When equilibrium is achieved between the undissolved CaF₂ and the solution, the calcium ion concentration was found to be 0.00021 M. Assuming that CaF₂ dissociates completely in water and there are no other important equilibria involving Ca²⁺ or F ? ions in the solution, calculate Ksp for calcium fluoride.
