[tamubsa]

Ksp for CaF2 is 3.9 x 10–11 and Ksp for PbF2 is 3.7 x 10–8. If 200 mL each of
5.0 x 10–3 M NaF, 2.0 x 10–5 M Ca(NO3)2 , and 3.0 x 10–3 M Pb(NO3)2
solutions are mixed,
 (a) only CaF2 will precipitate.
 (b) only PbF2 will precipitate.
 (c) both CaF2 and PbF2 will precipitate, and be visible.
 (d) both CaF2 and PbF2 will precipitate, but not be visible.
 (e) neither CaF2 nor PbF2 will precipitate


As many times as I do this, I get that CaF2 WILL precipitate, and PbF2 won't. After doing Ksp calculations, I found that .002 M of NaF was needed to precipitate the CaF2, and we have .0025 M, so it should precipitate. However, the answer is that neither of them precipitate. Am I missing something?

[Borek]

0.0025 M of NaF looks wrong to me. Hint: what is the final volume of the solution?

[tamubsa]

Ohhh, now I get it. Thank you so much!