Chapter 8, Problem 8.42NP

(a)

Interpretation Introduction

Interpretation: The vapor pressure of ${\text{I}}_{\text{2}}{}_{\left(\text{s}\right)}$ at 25.0°C needs to be determined if the sublimation pressure of ${\text{I}}_{\text{2}}{}_{\left(\text{s}\right)}$ is 0.30844 torr at25.0°Cand the enthalpy of sublimation is 56.30 kJ/mol. Also, it is assumed that the enthalpy of vaporization does not change with temperature.

  ${\text{C}}_{\text{p,m}}$ of the vapor and solid phase at that temperature are 36.9 and 54.4 J/K.

Concept Introduction: All substances can mainly exist in three phases; solid, liquid and gas. These three phases can convert into each other by the application of temperature and pressure such as heating of solid leads to the conversion to liquid and then gaseous state of matter.

Similarly, the gases can be compressed at high pressure to liquefy. The enthalpy change during the fusion of solid to liquid is called as enthalpy of fusion that is denoted as ${\text{ΔH}}_{\text{fus}}$ . Similarly, the enthalpy of vaporization involves in the vaporization of liquid to gas is called as enthalpy of vaporization that is denoted as ${\text{ΔH}}_{\text{vap}}$ .

(b)

Interpretation Introduction

Interpretation: The vapor pressure of ${\text{I}}_{\text{2}}{}_{\left(\text{s}\right)}$ at 25.0°C needs to be determined, if the sublimation pressure of ${\text{I}}_{\text{2}}{}_{\left(\text{s}\right)}$ is 0.30844 torr at25.0°C and the enthalpy of sublimation is 56.30 kJ/mol. Also, it is assumed that the enthalpy of vaporization at T is calculated from below equation:

  $\Delta {\text{H}}_{\text{sub}}\text{(T)}\text{}\text{ = }\Delta {\text{H}}_{\text{sub}}{\text{(T}}_{\text{0}}\text{)}\text{}+\Delta {\text{C}}_{\text{p}}{\text{(T-T}}_{\text{0}}\text{)}\text{}$

The values of ${\text{C}}_{\text{p,m}}$ of the vapor and solid phase at that temperature are 36.9 and 54.4 J/K respectively.

Concept Introduction: All substances can mainly exist in three phases; solid, liquid and gas. These three phases can convert into each other by the application of temperature and pressure such as heating of solid leads to the conversion to liquid and then gaseous state of matter.

Similarly, the gases can be compressed at high pressure to liquefy. The enthalpy change during the fusion of solid to liquid is called as enthalpy of fusion that is denoted as ${\text{ΔH}}_{\text{fus}}$ . Similarly the enthalpy of vaporization involves in the vaporization of liquid to gas is called as enthalpy of vaporization that is denoted as ${\text{ΔH}}_{\text{vap}}$ .