Chapter 19.1, Problem 19.1BFP

(a)

Interpretation Introduction

Interpretation:

The $\text{pH}$ of the given buffer solution prepared by mixing $\text{0}\text{.25 M }{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}{\text{NH}}_{\text{2}}\text{Cl}$ and $\text{0}\text{.30 M}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{NH}$ has to be calculated before the addition of 50.0 mL of $\text{0}\text{.75}\text{M}\text{HCl}$ to 1.0 L of the buffer $\left({\text{pK}}_{\text{b}}\text{of}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{NH}\text{=}\text{3}\text{.23}\right)$.

Concept Introduction:

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 $\text{pH}$ of the given buffer solution prepared by mixing $\text{0}\text{.25 M }{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}{\text{NH}}_{\text{2}}\text{Cl}$ and $\text{0}\text{.30 M}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{NH}$ has to be calculated after the addition of 50.0 mL of $\text{0}\text{.75}\text{M}\text{HCl}$ to 1.0 L of the buffer $\left({\text{pK}}_{\text{b}}\text{of}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{NH}\text{=}\text{3}\text{.23}\right)$.

Concept Introduction:

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.