Chapter 20, Problem 20.5P

Interpretation Introduction

Interpretation:

The reasons that why entropy changes of vaporization ${\text{ΔS}}_{\text{vap}}$ is larger than ${\text{ΔS}}_{\text{fus}}$ has to be explained.

Concept introduction:

In thermodynamics, free energy (Gibbs free energy) is the term that is used to explain the total energy content in a thermodynamic system that can be converted into work.  The free energy is represented by the letter G.

The equation given below helps us to calculate the change in free energy in a system.

$\text{ΔG = }\Delta {\rm H}\text{- T}\Delta \text{S}$

At a temperature of normal boiling point, the gaseous state of the system will be in equilibrium with the liquid state.  The free energy change in the system will be zero.  Taking the free energy value as zero, molar entropy of vaporization can be calculated using the following equation.

  ${\text{ΔS}}_{\text{vap}}\text{=}\frac{{\text{ΔΗ}}_{\text{vap}}}{{\text{T}}_{\text{bp}}}$

Where,

${\text{ΔS}}_{\text{vap}}$ is the entropy of vaporization

${\text{ΔΗ}}_{\text{vap}}$ is the enthalpy of vaporization

${\text{T}}_{\text{bp}}$ is the boiling temperature