Chapter 18, Problem 18.94P

(a)

Interpretation Introduction

Interpretation:

The higher $\text{pH}$ of the solution has to be identified from the given pairs, $\text{ 0}{\text{.1 M NiCl}}_{\text{2}}\text{ or 0}\text{.1 M NaCl}$.

Concept introduction:

An equilibrium constant $\left(K\right)$ is the ratio of concentration of products and reactants raised to appropriate stoichiometric coefficient at equlibrium.

The reaction of any base B with water is written as,

  $\text{B}\left(\text{aq}\right)+{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)\rightleftharpoons \text{BH}\left(\text{aq}\right)+{\text{OH}}^{-}\left(\text{aq}\right)$

The relative strength of an acid and base in water can be also expressed quantitatively with an equilibrium constant as follows:

$K_{\text{b}}=\frac{\left[\text{BH}\right]\left[{\text{OH}}^{-}\right]}{\left[\text{B}\right]}$

An equilibrium constant $\left(K\right)$ with subscript $\text{b}$ indicates that it is an equilibrium constant of the base in water.

  $\begin{array}{l}{\text{Acid - dissociation constants can be expressed as pK}}_a\text{ values,}\\ {\text{pK}}_a{\text{ = -log K}}_a\text{ and}\\ {\text{10}}^{{\text{ - pK}}_a}{\text{ = K}}_{\text{a }}\end{array}$

Percent dissociation can be calculated by using following formula,

  $\text{Percent dissociated = }\frac{\text{dissociation}}{\text{initial}}\text{×100}$

The ${\text{K}}_a$ value is calculating by using following formula,

  ${\text{K}}_{\text{w}}{\text{ = K}}_{\text{a}}{\text{ × K}}_{\text{b}}$

Acids strength is mainly depending on the dissociation of ions, strong acids dissociates completely and weak acid dissociate slightly.

The acid strength is depending on the ${\text{K}}_{\text{a}}$ value, if the ${\text{K}}_{\text{a}}$ value is larger the stronger the acid and it is lower $\text{pH}$. if the ${\text{K}}_{\text{a}}$ value is small the weaker the acid and it is higher $\text{pH}$.

(b)

Interpretation Introduction

Interpretation:

The higher $\text{pH}$ of the solution has to be identified in the given $\text{ 0}{\text{.1 M Sn(NO}}_{\text{3}}{\text{)}}_{\text{2}}\text{ or 0}{\text{.1 M Co(NO}}_{\text{3}}{\text{)}}_{\text{2}}$ pairs.

Concept introduction:

An equilibrium constant $\left(K\right)$ is the ratio of concentration of products and reactants raised to appropriate stoichiometric coefficient at equlibrium.

The reaction of any base B with water is written as,

  $\text{B}\left(\text{aq}\right)+{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)\rightleftharpoons \text{BH}\left(\text{aq}\right)+{\text{OH}}^{-}\left(\text{aq}\right)$

The relative strength of an acid and base in water can be also expressed quantitatively with an equilibrium constant as follows:

$K_{\text{b}}=\frac{\left[\text{BH}\right]\left[{\text{OH}}^{-}\right]}{\left[\text{B}\right]}$

An equilibrium constant $\left(K\right)$ with subscript $\text{b}$ indicates that it is an equilibrium constant of the base in water.

  $\begin{array}{l}{\text{Acid - dissociation constants can be expressed as pK}}_a\text{ values,}\\ {\text{pK}}_a{\text{ = -log K}}_a\text{ and}\\ {\text{10}}^{{\text{ - pK}}_a}{\text{ = K}}_{\text{a }}\end{array}$

Percent dissociation can be calculated by using following formula,

  $\text{Percent dissociated = }\frac{\text{dissociation}}{\text{initial}}\text{×100}$

The ${\text{K}}_a$ value is calculating by using following formula,

  ${\text{K}}_{\text{w}}{\text{ = K}}_{\text{a}}{\text{ × K}}_{\text{b}}$

Acids strength is mainly depending on the dissociation of ions, strong acids dissociates completely and weak acid dissociate slightly.

The acid strength is depending on the ${\text{K}}_{\text{a}}$ value, if the ${\text{K}}_{\text{a}}$ value is larger the stronger the acid and it is lower $\text{pH}$. if the ${\text{K}}_{\text{a}}$ value is small the weaker the acid and it is higher $\text{pH}$.