Calculate the Minimum Concentration of Mg²⁺ That Must Be Added

Multiple Choice

Calculate the minimum concentration of Mg²⁺ that must be added to 0.10 M NaF in order to initiate a precipitate of magnesium fluoride.(For MgF₂ , K_sp = 6.9 × 10^-9.)

A) 1.4 × 10⁷ M
B) 6.9 × 10^-9 M
C) 6.9 × 10^-8 M
D) 1.7 × 10^-7 M
E) 6.9 × 10^-7 M