Will a precipitate of magnesium fluoride form when 200.mL of 1.9 * 10^-3 M MgCl₂ are added to 300.mL of 1.4 * 10^-2 M NaF? [K_sp (MgF₂)= 6.9 * 10^-9]

Question

Quizplus · Accepted Answer

We can use the equation Q = [Mg2+][F-]2 to calculate the ion product (Q) of the reaction:
MgCl2 + 2 NaF → MgF2 + 2 NaCl

Initial concentrations:
[Mg2+] = (0.200 L)(1.9 mol/L) = 0.380 mol
[F-] = (0.300 L)(1.4 mol/L) = 0.420 mol

Q = (0.380 mol)(0.420 mol)2 = 0.067 mol3/L3

The equilibrium constant (Ksp) for MgF2 is 6.9 x 10-9. Since Q is greater than Ksp, the reaction will proceed until MgF2 precipitates out of solution. Hence, the best choice is A.

Will a Precipitate of Magnesium Fluoride Form When 200