Will a precipitate of magnesium fluoride form when 200.mL of 1.9 × 10^-3 M MgCl₂ are added to 300.mL of 1.4 × 10^-2 M NaF? [K_sp (MgF₂)= 6.9 × 10^-9]

Question

Quizplus · Accepted Answer

The first step is to write the chemical equation and the expression for the reaction quotient:

MgCl2(aq) + 2NaF(aq) → MgF2(s) + 2NaCl(aq)

Q = [Mg2+][F^-]^2

To calculate Q, we need to find the concentrations of the ions in the solution after mixing:

[Mg2+] = 1.9 × 10^-3 M × (200 mL)/500 mL = 0.76 × 10^-3 M
[F^-] = 1.4 × 10^-2 M × (300 mL)/500 mL = 0.84 × 10^-2 M

Substituting these values into the expression for Q:

Q = (0.76 × 10^-3 M)(0.84 × 10^-2 M)^2 = 5.10 × 10^-11

Since Q > Ksp for MgF2, a precipitate will form. Therefore, the correct answer is A: Yes, Q > Ksp.

Will a Precipitate of Magnesium Fluoride Form When 200