Determine the fluoride ion concentration for a saturated solution of magnesium fluoride. (Ksp = 7.4E-11)
To determine the fluoride ion concentration for a saturated solution of magnesium fluoride, we need to use the solubility product constant (Ksp) for magnesium fluoride.
The solubility product constant (Ksp) is the equilibrium constant for the dissolution of a sparingly soluble compound in water. For magnesium fluoride (MgF2), the Ksp value is given as 7.4E-11.
The balanced equation for the dissolution of magnesium fluoride is:
MgF2(s) ⇌ Mg2+(aq) + 2F-(aq)
We can assume that the saturated solution of magnesium fluoride is at equilibrium, and at this equilibrium, x mol/L of Mg2+ ions and 2x mol/L of F- ions are present in the solution.
Using the equation for Ksp:
Ksp = [Mg2+][F-]^2
Substituting the expressions for the concentrations in terms of x:
7.4E-11 = (x)(2x)^2
7.4E-11 = 4x^3
x^3 = 1.85E-11
x ≈ (1.85E-11)^(1/3)
x ≈ 1.34E-4
Therefore, the concentration of fluoride ions in a saturated solution of magnesium fluoride is approximately 1.34E-4 mol/L.