Chapter 16, Problem 16.72SP

(a)

Interpretation Introduction

Interpretation:

$\Delta G$ for vaporization of benzene $\left(\Delta G_{vap}\right)$  at $70°C$ has to be calculated.  Boiling of benzene at this temperature and $1\text{ atm}$ pressure has to be predicted.

Concept Introduction:

• Entropy refers to measurement of randomness or disorderliness in the system.  More the number of molecules in a system more will be the movement of molecules and greater will be the entropy given that weak intermolecular forces prevails between molecules.
• Entropy is denoted by ‘S’ and $\Delta S$  change in entropy.
• $\Delta S_{total}=\Delta S_{sys}+\Delta S_{surr}$

Where,

 $\begin{array}{l}\Delta S_{total}=total\text{ entropy change}\\ \Delta S_{sys}=\text{entropy change in system (reaction)}\\ \Delta S_{surr}=\text{entropy change in surroundings}\end{array}$

• $\Delta G$ refers to change in free energy. $\Delta H$ is change in enthalpy.  Both are related as,

$\Delta G=\Delta H-T\Delta S$

• Entropy of vaporization is represented as $\Delta S_{vap}$ and it refers to entropy change associated with vaporization of a liquid.  $\Delta S_{vap}$ is calculated as,

$\Delta S_{vap}=\frac{\Delta H_{vap}}{T}$

• Boiling point of a liquid substance is the temperature at which vapor pressure of the liquid becomes equal to the surrounding external pressure. 

(b)

Interpretation Introduction

Interpretation:

$\Delta G$ for vaporization of benzene $\left(\Delta G_{vap}\right)$  at $80°C$ has to be calculated.  Boiling of benzene at this temperature and $1\text{ atm}$ pressure has to be predicted.

Concept Introduction:

• Entropy refers to measurement of randomness or disorderliness in the system.  More the number of molecules in a system more will be the movement of molecules and greater will be the entropy given that weak intermolecular forces prevails between molecules.
• Entropy is denoted by ‘S’ and $\Delta S$  change in entropy.
• $\Delta H$ refers to change in enthalpy.  $\Delta S_{surr}$ and $\Delta H°$ are related as,

$\Delta S_{surr}=\frac{-\Delta H}{T}$

• Entropy of vaporization is represented as $\Delta S_{vap}$ and it refers to entropy change associated with vaporization of a liquid.  $\Delta S_{vap}$ is calculated as,

$\Delta S_{vap}=\frac{\Delta H_{vap}}{T}$

• Boiling point of a liquid substance is the temperature at which vapor pressure of the liquid becomes equal to the surrounding external pressure. 

(c)

Interpretation Introduction

Interpretation:

$\Delta G$ for vaporization of benzene $\left(\Delta G_{vap}\right)$ at $90°C$ has to be calculated.  Boiling of benzene at this temperature and $1\text{ atm}$ pressure has to be predicted.

Concept Introduction:

• Entropy refers to measurement of randomness or disorderliness in the system.  More the number of molecules in a system more will be the movement of molecules and greater will be the entropy given that weak intermolecular forces prevails between molecules.
• Entropy is denoted by ‘S’ and $\Delta S$  change in entropy.
• $\Delta H$ refers to change in enthalpy.  $\Delta S_{surr}$ and $\Delta H°$ are related as,

$\Delta S_{surr}=\frac{-\Delta H}{T}$

• Entropy of vaporization is represented as $\Delta S_{vap}$ and it refers to entropy change associated with vaporization of a liquid.  $\Delta S_{vap}$ is calculated as,

$\Delta S_{vap}=\frac{\Delta H_{vap}}{T}$

• Boiling point of a liquid substance is the temperature at which vapor pressure of the liquid becomes equal to the surrounding external pressure.