Chapter 18, Problem 18.41P

(a)

Interpretation Introduction

Interpretation:

The explanation has to be given for the ${\text{K}}_{\text{w}}$ change with rising temperature, and also heat is reactant or product has to be explained.

Concept introduction:

Autoionization:

The same molecule reacts and produces the ions, in general proton transfer takes place within the molecule.

(b)

Interpretation Introduction

Interpretation:

 ${\text{K}}_{\text{w}}\text{, }\left[{\text{OH}}^{\text{-}}\right]\text{, and pOH}$ has to be calculated for solution with a $\text{pH}$ of $6.80$.

Concept introduction:

The concentration of ${\text{H}}_{\text{3}}{\text{O}}^{+}$ is calculating by using following formula,

  ${\text{K}}_{\text{w}}{\text{ = K}}_{\text{a}}{\text{ × K}}_{\text{b}}$

  ${\text{K}}_{\text{w}}{\text{ = [H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{][OH}}^{\text{-}}\text{] = 1}\text{.0}\times {10}^{-14}$

The Relationships Among $\text{pH, pOH, and pKw}$

  $\begin{array}{l}\text{pH = -}\text{log}{\text{(H}}_{\text{3}}{\text{O}}^{\text{+}}\text{)}\\ \left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]={10}^{-\text{pH}}\\ \text{pOH = -}\text{log}{\text{(OH}}^{-}\text{)}\\ \left[{\text{OH}}^{-}\right]={10}^{-\text{pOH }}\end{array}$

  ${\text{pK}}_{\text{w}}\text{ = pH + pOH = 14}\text{.00 }$

The $\text{pH}$ is a unit of measure which describe the degree of alkanity or acidity of a solution.

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

A solution may be acidic and basic depends on relative strength of anions as an acid or base. Anions and cations can be acidic, basic and netural. Acidic have $\text{pH < 7}$, basic have $\text{pH > 7}$ and netural have $\text{pH=7}$.