Chapter 18, Problem 18.31P

Interpretation Introduction

Interpretation:

The number of moles has to be calculated for $\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]{\text{ or [OH}}^{\text{-}}\text{]}$ that is added to a liter of strong acid solution to adjust its $\text{pH}$ from $\text{3}\text{.15 to 3}\text{.65}$.

Concept introduction:

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 $\text{pH=7}$.

The $\text{pH}$ is decreases when the solution is more acidic similarly the $\text{pH}$ is increase when the solution is more basic.

One mole of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ ion reacts with one mole ${\text{OH}}^{\text{–}}$ ion, the difference in ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ will be equal to the ${\text{OH}}^{\text{–}}$ added.

Therefore,

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

Acid – dissociation constant can be expressed as ${\text{ pK}}_a$ values,

    $\begin{array}{l}{\text{pK}}_a{\text{ = -log K}}_a\text{ and}\\ {\text{10}}^{{\text{ - pK}}_a}{\text{ = K}}_{\text{a }}\end{array}$