Chapter 18, Problem 79IAE

Interpretation Introduction

Interpretation:

To prove by calculation that in acidic solution at intermediate $\text{pH}$ the concentration of ${\text{Al}}^{\text{3+}}$ ions decreases and in basic solution concentration of ${\left[\text{Al}{\left(\text{OH}\right)}_4\right]}^{-}$ increases results U-shaped curve.

Concept introduction:

Dissociation of aluminum hydroxide in acidic solution,

$\text{Al}{\left(\text{OH}\right)}_3\left(\text{s}\right)\rightleftharpoons {\text{Al}}^{\text{3+}}\left(\text{aq}\right)+3{\text{OH}}^{-}\left(\text{aq}\right)$

The solubility product expression for aluminum hydroxide is,

$K_{\text{sp}}\left(\text{Al}{\left(\text{OH}\right)}_3\right)\rightleftharpoons \left[{\text{Al}}^{\text{3+}}\right]{\left[{\text{OH}}^{-}\right]}^3$

Aluminim hydroxide dissolves in basic solution.

$\text{Al}{\left(\text{OH}\right)}_3\left(\text{s}\right)+{\text{OH}}^{-}\left(\text{aq}\right)\rightleftharpoons {\left[\text{Al}{\left(\text{OH}\right)}_4\right]}^{-}\left(\text{aq}\right)$