CaF2的Ksp=2.7*10^-11
CaF2 —(弱电离)— Ca^2+ + 2F-
假设CaF2的溶解度是C mol/L
则[Ca^2+]=C [F-]=2*C
C*(2*C)^2=2.7*10^-11
C=1.9*10^-4mol/L