Chapter 2, Problem 2.33P

(a)

Interpretation Introduction

Interpretation:

To determine the requirement of heat if the vessel has a negligible heat capacity when three-pound moles nitrogen at $70\text{°F}$, contained in a rigid vessel, is heated to $350\text{°F}$ and also if the vessel weighs $m_V=200\left({\text{lb}}_{\text{m}}\right)$ and has heat capacity of $C_{P_V}=0.12\left(\text{Btu}\right){\left(\text{lbmole}\right)}^{\text{-1}}{\left({}^{\text{ο}}\text{F}\right)}^{\text{-1}}$ .

Concept Introduction:

First law of thermodynamicsis based on the conservation of energy and:

  $\Delta U=Q-W$ where $\Delta U$ is the change in the internal energy of the system, $Q$ is the heat transferred to the system and $W$ is the work done.

So,

  $\begin{array}{c}\Delta U=Q-W\\ =Q-p\Delta V\end{array}$

For constant volume ( $\Delta V=0$ ),

  $\Delta U=Q$

(b)

Interpretation Introduction

Interpretation:

To determine the heat extracted from the system of Four-pound moles of nitrogen at $400\text{ °F}$ is contained in a piston/cylinder arrangement which is kept at constant pressure, to cool it to $150\text{ °F}$, if the heat capacity of the piston and cylinder is neglected.

Concept Introduction:

This a general case of cylinder and piston in which the temperature changes occur and concept of calorimetry is used little bit. First Law of Thermodynamics is applied to the system.