The Ksp of Al(OH)3 is 1.3 × 10⁻³³ . What is the minimum pH required to prevent precipitation of Al(OH)3 when [Al³⁺] = 0.
For Al(OH)3 Al³⁺ + 3OH- , Ksp = [Al³⁺][OH-]³ = 1.3 × 10⁻³³ . Given [Al³⁺] = 0.01 , 0.01 [OH-]³ = 1.3 × 10⁻³³ , [OH-]³ = 1.3 × 10⁻³¹ , [OH-] = (1.3 × 10⁻³¹)¹/³ ≈ 5.07 × 10⁻¹¹ . pOH = -log(5.07 × 10⁻¹¹) ≈ 10.3 , pH = 14 - 10.3 = 3.7 .
Ref: NCERT Class 11 Chemistry > Chapter 6: Equilibrium > Topic: Homogeneous and Heterogeneous Equilibria and Applications of Equilibrium Constant