Thermodynamics and Chemistry

CHAPTER 8 PHASE TRANSITIONS AND EQUILIBRIA OF PURE SUBSTANCES

8.2 PHASEDIAGRAMS OFPURESUBSTANCES 201

bc

s l g

g

l + g

scf

s + g

(^0) triple line
.V
=n/=
cm 3
mol
1
(^3500200)
T=
K
400
0
p

=bar

100

(a)

0 500 1000 1500 2000 2500 3000 3500

0

20

40

60

80

100

bc

.V=n/=cm^3 mol^1

.

p=

bar

l + g

g

scf

(b)

200 250 300 350 400

bc

T=K

s l

g

scf

(c)

Figure 8.2 Relations amongp,V=n, andTfor carbon dioxide.aAreas are labeled

with the stable phase or phases (scf stands for supercritical fluid). The open circle

indicates the critical point.

(a) Three-dimensionalp–.V=n/–Tsurface. The dashed curve is the critical isotherm

atT D304:21K, and the dotted curve is a portion of the critical isobar atp D

73:8bar.

(b) Pressure–volume phase diagram (projection of the surface onto thep–.V=n/

plane).

(c) Pressure–temperature phase diagram (projection of the surface onto thep–T

plane).

aBased on data in Refs. [ 124 ] and [ 3 ].