Chapter 18, Problem 18.79SP

Interpretation Introduction

(a)

Interpretation:

The values of $\Delta S_{\text{surr}}$ and $\Delta S_{\text{total}}$ for vaporization of benzene at $1050\text{ K}$ are to be calculated.

Concept introduction:

The relation of total entropy is as follows:

$\Delta S_{\text{total}}=\Delta S_{\text{system}}+\Delta S_{\text{surroundings}}$

Second law of thermodynamics gives criteria for spontaneity. It states that when sign of total entropy change is positive, the reaction is spontaneous. When sign of $\Delta S_{\text{total}}$ is negative, the reaction is nonspontaneous. Also, all reactions are at equilibrium when total entropy change is equal to 0.

Interpretation Introduction

(b)

Interpretation:

The values of $\Delta S_{\text{surr}}$ and $\Delta S_{\text{total}}$ for vaporization of benzene at $1074\text{ K}$ are to be calculated.

Concept introduction:

The relation of total entropy is as follows:

$\Delta S_{\text{total}}=\Delta S_{\text{system}}+\Delta S_{\text{surroundings}}$

Second law of thermodynamics gives criteria for spontaneity. It states that when sign of total entropy change is positive, the reaction is spontaneous. When sign of $\Delta S_{\text{total}}$ is negative, the reaction is nonspontaneous. Also, all reactions are at equilibrium when total entropy change is equal to 0.

Interpretation Introduction

(c)

Interpretation:

The values of $\Delta S_{\text{surr}}$ and $\Delta S_{\text{total}}$ for vaporization of benzene at $1100\text{ K}$ are to be calculated.

Concept introduction:

The relation of total entropy is as follows:

$\Delta S_{\text{total}}=\Delta S_{\text{system}}+\Delta S_{\text{surroundings}}$

Second law of thermodynamics gives criteria for spontaneity. It states that when sign of total entropy change is positive, the reaction is spontaneous. When sign of $\Delta S_{\text{total}}$ is negative, the reaction is nonspontaneous. Also, all reactions are at equilibrium when total entropy change is equal to 0.

d)

Interpretation Introduction

Interpretation:

Whether the $\text{NaCl}$ melts at $1100\text{ K}$ or not should be determined. Also, the values of melting point of $\text{NaCl}$ is be calculated.

Concept introduction:

The relationship between $\Delta H$ and $\Delta S$ is as follows:

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

Where,

• $\Delta G$ is free energy change.
• $\Delta H$ is enthalpy change.
• $T$ is temperature.
• $\Delta S$ is change in entropy.

The entropy criteria for spontaneous change at constant $T$ and $P$ can also be stated with respect to free energy change as follows:

(1) When $\Delta G<0$, reaction is spontaneous.

(2) When $\Delta G>0$, reaction is nonspontaneous.

(3) When $\Delta G=0$, reaction is at equilibrium.