Chapter 2.6, Problem 24P

(A)

Interpretation Introduction

Interpretation:

Estimate the change in enthalpy.

Concept Introduction:

Write the expression of change in enthalpy $\left(\Delta H\right)$.

$\Delta H=\Delta H_{25°\text{F}\to 50°\text{F}}+\Delta H_{\text{fus}}+\Delta H_{50°\text{F}\to 150°\text{F}}+\Delta H_{\text{vap}}+\Delta H_{150°\text{F}\to 200°\text{F}}$

Here, change in enthalpy of fusion is $\Delta H_{\text{fus}}$ and change in enthalpy of vaporization is $\Delta H_{\text{vap}}$.

Write the expression of change in specific enthalpy $\left(\Delta \widehat{H}\right)$.

$\begin{array}{l}\Delta \widehat{H}=\frac{\Delta H}{M}\\ \frac{\Delta H}{M}=\frac{C_{P}dT}{M}\end{array}$

Here, mass is M, change in temperature is dT, and constant pressure heat capacity on a molar basis is $C_P$.

Write the expression to obtain the mass $\left(M\right)$.

$M=N\times MW$

Here, number of moles in the system is N.

(B)

Interpretation Introduction

Interpretation:

Estimate the change in internal energy.

Concept Introduction:

Write the expression of change in internal energy.

$\begin{array}{c}\Delta \widehat{U}=\Delta \widehat{H}-P\Delta \widehat{V}\\ =\Delta \widehat{H}-P\left({\widehat{V}}_V-{\widehat{V}}_S\right)\end{array}$

Here, pressure is P, vapor phase of specific volume is ${\widehat{V}}_V$, and solid phase of specific volume is ${\widehat{V}}_S$.

Write the value of ${\widehat{V}}_V$.

$\begin{array}{c}{\widehat{V}}_V=\frac{\underset{\_}{V}}{MW}\\ =\frac{RT}{P\left[MW\right]}\end{array}$

Here, gas constant is R and temperature is T.