Thermodynamics and Chemistry

CHAPTER 9 MIXTURES

9.4 LIQUID ANDSOLIDMIXTURES OFNONELECTROLYTES 251

reference state b

0

0:1

0:2

0:3

0:4

0 0:2 0:4 0:6 0:8 1:0

xB

(a)

.

fB

=bar

kH,B

0

0:1

0:2

0:3

0:4

0 0:2 0:4 0:6 0:8 1:0

xB

(b)

.f

=xB

/=B

bar

Figure 9.7 Liquid solutions of 2,3-dimethylbutane (B) in cyclooctane at298:15K

and 1 bar.a

(a) Fugacity of B in an equilibrated gas phase as a function of solution composition.

The dashed line, tangent to the curve atxBD 0 , is Henry’s law behavior, and its slope

iskH,B.

(b) Fugacity divided by mole fraction as a function of composition; the limiting value

atxBD 0 is the Henry’s law constantkH,B.

aBased on data in Ref. [ 109 ].

is proportional to all three of these composition variables. This leads to three versions of
Henry’s law:

mole fraction basis fBDkH,BxB (9.4.16)

(nonelectrolyte solute

at infinite dilution)

concentration basis fBDkc;BcB (9.4.17)

(nonelectrolyte solute

at infinite dilution)

molality basis fBDkm;BmB (9.4.18)

(nonelectrolyte solute

at infinite dilution)

In these equationskH,B,kc;B, andkm;Bare Henry’s law constants defined by

mole fraction basis kH,B defD lim

xB! 0



fB

xB



(9.4.19)

concentration basis kc;B defD lim

cB! 0



fB

cB



(9.4.20)

molality basis km;B defD lim

mB! 0



fB

mB



(9.4.21)