The mineral CaF2 has a solubility of 2.1 x 10^4 M. What is the Ksp of CaF2?
a. 1.85x10^11
b. 9.3x10^12
c. 3.7x10^11
d. 8.8x10^3
1 answer

CaF2 ==> Ca^+2 + 2F^
Ksp = (Ca^+2)(F^)^2
You know solubility CaF2 = 2.1 x 10^4; therefore, (Ca^+2) = 2.1 x 10^4. Since (F^) is twice that, (F^) = 4.2 x 10^4. Plug those values into the Ksp expression I wrote above and solve for Ksp. Post your work if you get stuck.