Question

The equilibrium concentration of hydroxide ion in a saturated aluminum hydroxide solution is _______M. The KSP of aluminum hydroxide is 1.9 × 10^{-33. That is all the information given to me.}

Answer 1

Al(OH)₃ KSP = 1.9 x 10^-33

Al(OH)₃   $\rightleftharpoons$    Al³⁺ + 3OH^-

Let S be the solubility

KSP = S x (3S)³ = 27S⁴

1.9 x 10^-33 = 27S⁴

S = 2.89 x 10^-9

[OH^-] = 3S = 3 x 2.89 x 10^-9 = 8.68 x 10^-9 M

Equilibrium concentration of hydroxide ion in a saturated aluminum hydroxide solution is 8.68 x 10^-9 M