Take the 1 Liter solution saturated with the magnesium fluoride from the previous problem. Filter out the precipitate. Now we have just a saturated solution of magnesium fluoride with zero precipitate.
At this point we have magnesium ions in solution and fluoride ions in solution. Remember the Ksp of MgF2 is equal to 3.7 x 10^-8 at room temperature.
If we add in 5 grams of magnesium sulfate (which will dissolve because it is a soluble compound that goes by the name of Epson salt, MgSO4) we will change the solubility of the magnesium fluoride due to the common ion effect. With this in mind, calculate how many grams of the magnesium fluoride that will stay dissolved in the composite solution.
Hint: In your equation X << 0.04
1. about 0.003 grams of MgF2 will stay in solution
2. about 0.004 grams of MgF2 will stay in solution
3. about 0.007 grams of MgF2 will stay in solution
4. about 0.045 grams of MgF2 will stay in solution
5. about 0.03 grams of MgF2 will stay in solution