Chapter 17, Problem 17.129SP

Interpretation Introduction

Interpretation:

Whether $\text{Mg}{\left(\text{OH}\right)}_2$ will precipitate or not is to be identified.

Concept introduction:

Solubility product is equilibrium constant for reactions that occur when an ionic compound is dissolved to produce ions. It is denotedby $K_{\text{sp}}$. Consider ${\text{A}}_x{\text{B}}_y$ an ionic compound. Its dissociation occurs as:

${\text{A}}_x{\text{B}}_y\rightleftharpoons x{\text{A}}^{y+}+y{\text{A}}^{x-}$

The expression for its $K_{\text{sp}}$ is as follows:

$K_{\text{sp}}={\left[{\text{A}}^{y+}\right]}^x{\left[{\text{B}}^{x-}\right]}^y$

A precipitate of an ionic compound will form when solution that contains constituent ion is mixed. The precipitation depends on value of ion product (IP). The IP is defined in the same way as $K_{\text{sp}}$. Also, the concentrations in expression for IP are concentration at time t and not equilibrium concentrations. Consider ${\text{A}}_x{\text{B}}_y$ to be an ionic compound. Its dissociation occurs as follows:

${\text{A}}_x{\text{B}}_y\rightleftharpoons x{\text{A}}^{y+}+y{\text{A}}^{x-}$

The expression for its IP is as follows:

$\text{IP}={\left[{\text{A}}^{y+}\right]}_t{}^x{\left[{\text{B}}^{x-}\right]}_t{}^y$

The negative logarithm of molar concentration of hydronium ion is called $\text{pH}$. The expression for pH is as follows:

$\text{pH}=-{\text{log}}_{\text{10}}\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

The relation between $\text{pH}$ and $\text{pOH}$ is as follows:

$\text{pH}+\text{pOH}=\text{14}$