Final answer:
To calculate the minimum pH needed to precipitate from a 0.1000-m solution so completely, consider the solubility product constant (Ksp) and the common ion effect.
Step-by-step explanation:
To calculate the minimum pH needed to precipitate from a 0.1000-m solution so completely that the concentration of the remaining ions is less than 0.2 mg per litre, we need to consider the solubility product constant (Ksp) and the common ion effect.
By comparing the ion product [Mg²+][F¯]² with Ksp, we can determine if precipitation will occur. If the ion product is larger than Ksp, precipitation will occur. If the ion product is smaller than Ksp, no precipitation will occur.
Further calculations are necessary to determine the exact minimum pH.