Chapter 18, Problem 18.75QP

Interpretation Introduction

Interpretation:

This has to be using the thermodynamic data, ethanol vapor pressure value has to be calculated at ${25}^{°}C$.

Concept Introduction:

Vapour pressure: Vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in closed system.  Vapour pressure is nothing but the tendency of particles to escape from the liquid (or) solid.

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