Question
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
a. 1.85x10^-11
b. 9.3x10^-12
c. 3.7x10^-11
d. 8.8x10^-3
Answers
DrBob222
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.
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.