Ksp Equation for CaF2: Coefficients and Stoichiometry Explained

[staka]

CaF2⇔Ca+2F.
Many places state that Ksp=[Ca][2F]^2; Ksp=[x]*[2x]^2.
I thought the coefficient go into Ksp equation as an exponent. So, Ksp=[Ca][F]^2.

Can anyone explain which is correct, or why [2F]^2 (if that's the correct one)?

 

[Borek]

Many places state that Ksp=[Ca][2F]^2

That's wrong. Are you sure you are not misreading:

Ksp=[x]*[2x]^2.

which is correct - assuming x is molar solubility of CaF₂.

Ksp=[Ca][F]^2.

That's correct.

 

[staka]

Why do we get Ksp=[x]*[2x]^2?
(Ksp=[Ca][2F]^2 is from this.. misread wrong)

 

[Borek]

Simple stoichiometry. If x moles of CaF₂ are dissolved - how many moles of Ca²⁺? How many moles of F^-?