Question

Question #d71a4

Answer 1

`K_(sp) = [Ca^(2+)][F^-]^2`

Explanation:

First consider how the compound will dissolve in water - or rather, how it dissociates into its smaller ionic components due to it being an ionic compound,

`CaF_2 (s) rightleftharpoons Ca^(2+)(aq) + 2F^(-)(aq)`

On the left of the equation is the reactant, and on the right, the products. The reactant is a solid, so it will not be included in the solubility equation.

`K_(sp) = [Ca^(2+)][F^-]^2`

In one mole of `CaF_2`, there is one mole of `Ca^(2+)` ions and two moles of `F^-` ions. Notice in the equation, the coefficient for the fluoride ions becomes an exponent.