Chapter 8, Problem 8.24NP

(a)

Interpretation Introduction

Interpretation:

The enthalpy of vaporization ΔH_vap and the enthalpy of sublimation ΔH_subneed to be calculated from the given data

Concept Introduction:

Vaporization and sublimation are phase transition reactions which involve a change in the state of a substance from the liquid to the vapor/gas phase and from the solid to the gas phases respectively

Enthalpy changes associated with the reaction is essentially the amount of heat energy required for the phase transition. These are denoted as ΔH_vapfor vaporization and ΔH_sub for sublimation.

The relationship between pressure (P), temperature (T) and the enthalpy change ( ΔH) is given via the Clausius-Clapeyron equation:

  $\text{lnP = }\frac{-\text{ΔH}}{\text{R}}\left(\frac{\text{1}}{\text{T}}\right)\text{ + C -----(1)}$

Where R = 8.314 J/mol-K and C is a constant.

(b)

Interpretation Introduction

Interpretation:

The enthalpy of fusion ΔH_fus for the solid needs to be calculated from the given data

Concept Introduction:

Fusion is a phase transition process which involves the change in state from solid to liquid.

The amount of heat energy required for the phase change or the melting process is referred to as the enthalpy of fusion ΔH_fus

(c)

Interpretation Introduction

Interpretation:

The temperature and pressure at the triple point needs to be calculated

Concept Introduction:

Triple point is a thermodynamic space in which solid, liquid and gaseous phases of a substance coexist

At the triple point:

vapor pressure of the solid = Vapor pressure of the liquid