Final answer:
Calcium fluoride (CaF2) will be least soluble in the solution with the highest concentration of a common ion. Therefore, CaF2 will be least soluble in the 0.10 M Ca(NO3)2 solution due to the common ion effect.
Step-by-step explanation:
The question asks in which solution CaF2 will be least soluble. We need to consider the common ion effect, where the solubility of a sparingly soluble salt is reduced by the presence of a common ion. For CaF2, which dissociates into Ca2+ and 2F-, its solubility will be most affected in a solution containing either of these ions.
Option a contains a calcium ion source, Ca(NO3)2, at a concentration of 0.10 M. Option b contains a fluoride ion source, NaF, at a concentration of 0.01 M. Option c is presumably a typo and should be disregarded. Option d contains Ca(NO3)2 at a concentration of 0.010 M. Since the common ion effect is more pronounced at higher concentrations, CaF2 will be least soluble in the solution with the highest concentration of a common ion, which is option a, the 0.10 M Ca(NO3)2 solution.