Chapter 16, Problem 16.78SP

(a)

Interpretation Introduction

Interpretation:

$\Delta H°,\Delta S°,\Delta G°$ for oxidation of gaseous $N_2$ has to be calculated and spontaneity of the reaction under standard-state conditions has to be ascertained.

Concept Introduction:

• $\Delta S°$ refers to standard entropy of the reaction which is termed as entropy change in a reaction under standard conditions of $298K$ and $1\text{ atm}$ pressure.  It is represented as,

$\Delta S°=S°\left(products\right)-S°\left(reac\tan ts\right)$

• $\Delta H°$ refers to standard enthalpy change.  Change in enthalpy in a reaction and heat of formation are related by the formula,

$\Delta H_{rxn}^{°}=\Sigma \Delta H_f^{°}(product)-\Sigma \Delta H_f^{°}(reac\tan t)$

Where,

$\begin{array}{l}\Delta H_{rxn}^{°}=\text{ enthalpy change in reaction}\\ \Delta H_f^{°}(product)=\text{ enthalpy or heat of formation of product}\\ \Delta H_f^{°}(reac\tan t)=\text{ enthalpy or heat of formation of }reac\tan t\end{array}$

• Standard free energy change, $\Delta G°,$ is represented as,

$\Delta G°=\Delta H°-T\Delta S°$

Where,

$\begin{array}{l}\Delta H°=\text{ standard enthalpy change}\\ \Delta \text{S}°\text{= standard entropy change}\end{array}$

• Spontaneous process has positive entropy value and negative free energy, enthalpy value.
• Non-spontaneous process tends to proceed with negative entropy value and positive free energy and enthalpy.

(b)

Interpretation Introduction

Interpretation:

$\Delta H°,\Delta S°,\Delta G°$ for dissociation of solid $KCl{O}_3$ has to be calculated and spontaneity of the reaction under standard-state conditions has to be ascertained.

Concept Introduction:

• $\Delta S°$ refers to standard entropy of the reaction which is termed as entropy change in a reaction under standard conditions of $298K$ and $1\text{ atm}$ pressure.  It is represented as,

$\Delta S°=S°\left(products\right)-S°\left(reac\tan ts\right)$

• $\Delta H°$ refers to standard enthalpy change.  Change in enthalpy in a reaction and heat of formation are related by the formula,

$\Delta H_{rxn}^{°}=\Sigma \Delta H_f^{°}(product)-\Sigma \Delta H_f^{°}(reac\tan t)$

Where,

$\begin{array}{l}\Delta H_{rxn}^{°}=\text{ enthalpy change in reaction}\\ \Delta H_f^{°}(product)=\text{ enthalpy or heat of formation of product}\\ \Delta H_f^{°}(reac\tan t)=\text{ enthalpy or heat of formation of }reac\tan t\end{array}$

• Standard free energy change, $\Delta G°,$ is represented as,

$\Delta G°=\Delta H°-T\Delta S°$

Where,

$\begin{array}{l}\Delta H°=\text{ standard enthalpy change}\\ \Delta \text{S}°\text{= standard entropy change}\end{array}$

• Spontaneous process has positive entropy value and negative free energy, enthalpy value.
• Non-spontaneous process tends to proceed with negative entropy value and positive free energy and enthalpy.

(c)

Interpretation Introduction

Interpretation:

$\Delta H°,\Delta S°,\Delta G°$ for oxidation of ethanol has to be calculated and spontaneity of the reaction under standard-state conditions has to be ascertained.

Concept Introduction:

• $\Delta S°$ refers to standard entropy of the reaction which is termed as entropy change in a reaction under standard conditions of $298K$ and $1\text{ atm}$ pressure.  It is represented as,

$\Delta S°=S°\left(products\right)-S°\left(reac\tan ts\right)$

• $\Delta H°$ refers to standard enthalpy change.  Change in enthalpy in a reaction and heat of formation are related by the formula,

$\Delta H_{rxn}^{°}=\Sigma \Delta H_f^{°}(product)-\Sigma \Delta H_f^{°}(reac\tan t)$

Where,

$\begin{array}{l}\Delta H_{rxn}^{°}=\text{ enthalpy change in reaction}\\ \Delta H_f^{°}(product)=\text{ enthalpy or heat of formation of product}\\ \Delta H_f^{°}(reac\tan t)=\text{ enthalpy or heat of formation of }reac\tan t\end{array}$

• Standard free energy change, $\Delta G°,$ is represented as,

$\Delta G°=\Delta H°-T\Delta S°$

Where,

$\begin{array}{l}\Delta H°=\text{ standard enthalpy change}\\ \Delta \text{S}°\text{= standard entropy change}\end{array}$

• Spontaneous process has positive entropy value and negative free energy, enthalpy value.
• Non-spontaneous process tends to proceed with negative entropy value and positive free energy and enthalpy.