Chapter 2, Problem 2A.3E

(a)

Interpretation Introduction

Interpretation:

The work done when gas expands isothermally against a constant external pressure has to be determined.

Concept Introduction:

The force F, opposing an expansion under constant external pressure $p_{ex}$, then $F=p_{ex}A$

The work done is the force when multiplies by the distance moved, is given by

$\begin{array}{l}Workdone,w=Force\times \text{Distance}\\ \\ w=-p_{ex}A\times hwhere,h\times A=\Delta V\\ \\ \therefore w=-p_{ex}\times \Delta V\end{array}$

(b)

Interpretation Introduction

Interpretation:

The work done by the gas when volume is expanded from initial volume to final volume at temperature T has to be determined.

Concept Introduction:

For an isothermal reversible expansion of a perfect gas from initial volume to final volume at temperature T is given by

  $w=-nRT\ln \frac{V_f}{V_i}$