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.

S = 0.2 E-7 M

Explanation:

          S              S         2S + 0.4

∴ [F-] = 0.4 m = 0.4 mol/Kg

∴ solvent: H2O ⇒ δH2O = (997 Kg/m³)*(m³/1000L) = 0.997 Kg/L

⇒ [F-] = (0.4 mol/Kg)*(0.997 Kg/L) = 0.3988 M ≅ 0.4 M

∴ Ksp = 6.4 E-9 = [S]*[2S + 0.4]²

⇒ 6.4 E-9 = (S)*(4S² + 1.6S + 0.16)

⇒ 6.4 E-9 = 4S³ + 1.6S² + 0.16S

⇒ 4S³ + 1.6S² + 0.16S - 6.4 E-9 = 0

⇒ S = 0.2 E-7 M

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.