Calculate the solublity for Al (OH)_3 given a Ksp= 0.0000000000106 in a buffered solution with pH= 12.3

Question

Calculate the solublity for Al (OH)_3 given a Ksp= 0.0000000000106 in a buffered solution with pH= 12.3

Answer 1

Al(OH)₃(s)<==> Al³⁺(aq) + 3OH^-(aq)

Ksp = [Al³⁺][OH-}³

From the pH, we can determine the [OH-] as follows:

pH = 12.3 therefore pOH = 1.7 and [OH-] = 1x10^-1.7 = 2x10^-2 M

Ksp = 1.06x10^-11 = [Al³⁺][2x10^-2]³

1.06x10^-11 = [Al³⁺][2x10^-2]³

[Al³⁺] = 2.65x10^-8 M = solubility of Al(OH)₃ in pH 12.3 buffer