This preview shows pages 1–2. Sign up to view the full content.
Figure 4.8(b) in CAQS
The reaction described is the generic:
)
(
)
(
g
X
g
W
⇔
.
Assume
T = 298 K
.
The stoichiometry is such that the total pressure is constant; that is, when some amount of
W(g) is consumed, the same amount of X(g) is formed and viceversa.
The figure
suggests that, for simplicity:
atm
p
p
X
W
1
=
+
To supply some actual values, let us assert that:
mol
kJ
G
mol
kJ
G
X
W
/
23
/
22
=
=
These values could be obtained as delta G of formation for X, W for actual molecules.
In
the text figure, we are simply given the value of K in the figure text but I wanted to
illustrate for you how one might compute K from other information provided or available
from tables.
For our reaction, then:
mol
kJ
G
G
G
W
X
rxn
/
00
.
1
+
=

=
∆
.
Then,
67
.
0
exp
ln
=
∆

=

=
∆
RT
G
K
K
RT
G
rxn
rxn
Please note:
•
rxn
G
∆
is the “chemical force” acting upon the reaction IF one were to have BOTH
W(g)
and
X(g)
present; unmixed; and in their standard states (at 1 atm).
This
actual composition appears NOWHERE on our figure.
Where we have
W
p
=1.0
atm on the figure has
X
p
= 0.0 atm.
•
Bullet one notwithstanding, the value of
rxn
G
∆
tells us something about the
equilibrium composition; more specifically, the value of K, the equilibrium
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '07
 Warren
 Chemistry, Stoichiometry

Click to edit the document details