Chapter 10, Problem 10.113EP

Interpretation Introduction

Interpretation:

When added small amount of strong acid the changes of buffer solution concentration has to be discussed.

Concept Introduction:

A buffer is an aqueous solution containing substances that prevent major changes in solution pH when small amounts of acid or base are added to it.

pH definition:

The concentration of hydrogen ion is measured using $\text{pH}$ scale.  The acidity of aqueous solution is expressed by $\text{pH}$ scale.

The value $\text{pH}$ of a solution is defined as the negative base-10 logarithm of the hydrogen or hydronium ion concentration.

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

Based on the pH value, a solution can be classified as acidic, basic or neutral solution.

  $\begin{array}{l}\text{pH < 7, acidic solution}\\ \\ \text{pH > 7, basic solution}\\ \\ \text{pH = 7, neutral solution}\end{array}$

Strong acid:

In strong acids, the ionization of acid is complete.  This implies that the concentration of the hydrogen ion or hydronium ion will be equal to the initial concentration of the acid at equilibrium.

Weak acid:

In weak acids, the ionization of acid is not complete.  This implies that the concentration of the hydrogen ion or hydronium ion will not be equal to the initial concentration of the acid at equilibrium.

For strong acids the concentration of acid will be same as that of the concentration of hydrogen ions, because strong acids undergo complete ionization.

In case of weak acid, the concentration of hydrogen ion will be less than the concentration of given acid; since weak acid does not ionize completely.