Solubility?

Question

What is the solubility of Al(OH)3 (Ksp= 3*10-34) in a slightly basic solution with pH of 8.44, in M?

Answer 1

Al(OH)3 <=> Al+3 +3OH-

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

if s is the molar solubility of Al(OH)3 then [Al+3]=s

pOH= 14-pH= 14-8.44 =5.56 =>
[OH-] =10^-pOH= 10^-5.56

thus Ksp=s*(10^-pOH)^3=>
s= Ksp*(10^(3pOH)) =
=3*(10^-34)*10^(3*5.56) =
=3*10^-17.32 =1.44*10^-17 M