Question

The solubility of Al(OH)3 is measured and found to be 2.22×10-7 g/L. Use this information to calculate a Ksp value for aluminum hydroxide.

Answer 1

S = 2.22 x 10^-7 g / L

molar mass of Al(OH)3 = 78.0 g / mol

molarity of Al(OH)3 = 2.22 x 10^-7 g / L / 78.0 g / mol

                                = 2.85 x 10^-9 mol / L

Al(OH3) ----------------------------> Al+3 + 3OH-

Ksp = [Al+3] [OH-]^3

Ksp = (S)(3S)^3

Ksp = 27 S^4

KSp = 27 x (2,85 x 10^-9)^4

Ksp = 1.77 x 10^-33