154
DOC.
4
KINETIC THEORY LECTURE NOTES
We found earlier
»=
-pcX
3
St
Comparison
yields
-
=
p.
This
relation
also
proves
to
be
correct to
an
order of
magnitude[21]
St
Mean
Dobserved Dcalculated
O2
1.88
.
10-4
N2
1.66
10-4
1.77
.10-4
0.17 0.13
[p. 8]
Path
Length
and Actual
Size of
Molecules[22]
8t=
ipcX
3
p
=
density.
Approximately
c
=
3RT
N
M
1
X
can
be calculated.
e.g., oxygen
atmospheric pressure
10-4
mm.
Since
now
A.
=
4
-7Ü7Z2
3
X
also
yields s2n,
and thus
s2N
=
-
=
-
-
11
N
If molecules
are
packed perfectly
tightly,
then
molecule
occupies roughly
the
space
s3.
The
value
for
all
molecules of
a
gram-molecule
therefore
s3N.
Hence
we
have
s2N
=
A
(from path length)
s3N
=
V
(approximate
molecular volume
in
the
solid
or
liquid
state.)