Chapter 19, Problem 19.33P

(a)

Interpretation Introduction

Interpretation:

A solution made by mixing $\text{50}\text{.0 }mL$ of $0.050\text{M}{\text{NaHCO}}_3$ and $0.10\text{mL}$ of $0.10M$ sodium hydroxide $pH$ has to be calculated.

Concept Introduction:

pH definition:

The pH of a solution is defined as the negative base-10 logarithm of the hydronium ion ${\text{[H}}_{\text{3}}{\text{O}}^{+}\text{]}$ concentration.

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

Henderson-Hasselbalch equation:

The $\text{pH}$ at an intermediate stage of the titration is calculated by using the following equation,

  $\begin{array}{l}\text{pH}\text{=}{\text{pK}}_{\text{a}}\text{+}\text{log}{\frac{\left[\text{base}\right]}{\left[\text{acid}\right]}}_{}^{}\\ \text{where,}\\ \text{pH}\text{=}\text{-}\text{log}\left[{\text{H}}^{\text{+}}\right]\\ {\text{pK}}_{\text{a}}\text{=}\text{-}\text{log}{\text{K}}_{\text{a}}\\ \left({\text{K}}_{\text{a}}\text{-}\text{acid}\text{dissociation}\text{constant}\right)\end{array}$

This equation is known as Henderson-Hasselbalch equation.

(b)

Interpretation Introduction

Interpretation:

The amount of $HCl$ must be added to $25.0mL$ of the buffer change the $pH$ by $0.07$ units has to be identified.

Concept Introduction:

pH definition:

The pH of a solution is defined as the negative base-10 logarithm of the hydronium ion ${\text{[H}}_{\text{3}}{\text{O}}^{+}\text{]}$ concentration.

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

Buffer solution:

• Buffer solution is defined as a solution that oppose changes in $\text{pH}$ while adding little amount of either an acid or a base. In general, addition of acid or base does not affect the $\text{pH}$ in buffer solution but if it is more than amount of conjugate base or conjugate acid, then buffer loses its buffering capacity.
• Buffer solution is a combination of a weak acid and its conjugate base or a weak base and its conjugate acid.