Question

What is the molar solubility of magnesium fluoride in a solution that is 0.40 m f− ions? the ksp of mgf2 is 6.4 × 10−9. hints what is the molar solubility of magnesium fluoride in a solution that is ions? the of is . 8.0 × 10−9 8.0 × 10−5 1.6 × 10−8 4.0 × 10−8?

Answer 1

Answer: MgF2 ====⇒ Mg+2 + 2F- Ksp = [Mg+2][F-]^2 Let S = molar solubility of MgF2 [Mg+2] = S ; [F-] = 2s Since the [F-] is initially 0.40 M, then [F-] = 0.40 + 2S 6.4 x 10^-9 = (S) (0.40 + 2S)^2 ; one can neglect the 2S in the 0.40 + 2S expression since it is very, very small compared to the 0.40 already present. 6.4 x 10^-9 = S(0.40)^2 S = 4.0 x 10^-8 Molar solubility = 4.0 x 10^-8