Chapter 16, Problem 16.118QP

(a)

Interpretation Introduction

Interpretation:

The increasing order of ${\text{K}}_{\text{a}}$, the given weak acids have to be arranged.

Concept Introduction:

${\text{K}}_{\text{a}}$ is known as the acid dissociation constant and its value decides the strength of an acid. If the value of ${\text{K}}_{\text{a}}$ is larger than the acid is said to be a strong acid. If the value of ${\text{K}}_{\text{b}}$ is smaller than the acid is said to be a weak acid.

(b)

Interpretation Introduction

Interpretation:

The increasing order of ${\text{K}}_{\text{b}}$, the conjugate bases have to be arranged.

Concept Introduction:

The removal of one proton from a acid results in the formation of a negatively charged species. It is known as a conjugate base of the acid.

${\text{K}}_{\text{b}}$ is known as the base dissociation constant and its value decides the strength of a base. If the value of ${\text{K}}_{\text{b}}$ is larger than the base is said to be a strong base. If the value of ${\text{K}}_{\text{b}}$ is smaller than the base is said to be a weak base.

(c)

Interpretation Introduction

Interpretation:

The percentage ionization for each acid have to be calculated.

Concept Introduction:

Percent ionization is the measure of strength of a weak acid. It can be calculated using the formula as shown below:

$\begin{array}{c}\text{\%}\text{ionization}\text{=}\frac{{\left[{\text{H}}^{\text{+}}\right]}_{\text{equilibrium}}}{{\left[\text{HA}\right]}_{\text{o}}}\\ \text{Where,}\\ {\left[{\text{H}}^{\text{+}}\right]}_{\text{equilibrium}}\text{=}\text{Hydrogen}\text{ion}\text{concentraion}\text{at}\text{equilibrium}\text{.}\\ {\left[\text{HA}\right]}_{\text{o}}\text{=}\text{Initial}\text{concentration}\text{of}\text{the}\text{weak}\text{acid}\text{.}\end{array}$

(d)

Interpretation Introduction

Interpretation:

Among the sodium salt of the given acids the one with the lowest $\text{pH}$ has to be found.

Concept Introduction:

$\text{pH}$ is the negative logarithm of concentration of ${\text{H}}^{\text{+}}$ ion in a solution.

It can be expressed as

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

From the value of $\text{pH}$, a given solution can be determined as acidic, basic or neutral as shown below:

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