PHYSICAL CHEMISTRY IN BRIEF

CHAP. 4: APPLICATION OF THERMODYNAMICS [CONTENTS] 107

Chapter 4

Application of thermodynamics

4.1 Work.

4.1.1 Reversible volume work

The reversible volume work,Wvolis connected with a change of the system volume from the

initial valueV 1 to the final valueV 2. We have

Wvol=−

∫V 2

V 1

pdV , (4.1)

wherepis the pressure of the system.
U Main unit:J

Note: It follows from the equation that during compressionp > 0 , V 2 < V 1 , Wvol > 0

(work is supplied to the system), during expansionp > 0 , V 2 > V 1 , Wvol<0 (work is done

by the system), which is in compliance with the usage1.2.

Work is not a state function [see3.3.2] and its value does not depend on the initial (p 1 , V 1 )

and final (p 2 , V 2 ) state only, but also on the path. In terms of mathematical expression it means

that in (4.1) we need to know the dependence of the integrand on the integration variable,

p=f(V). Several examples of the specification ofp=f(V) and calculation ofWvolare given

below.