165
TABLE 11-1
Vapor Pressures of Water at Various Temperatures
f (°C)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
P (torr)
458
4.93
529
569
6 10
654
701
751
805
861
921
984
105
',1 2
120
t ( C)
15
16
17
18
19
20
21
22
23
24
25
26
27
28
P (torr)
12 8
136
14 5
155
165
175
187
198
21 1
224
238
252
267
283
f (C)
29
30
31
32
33
34
35
40
50
60
70
80
90
100
P (torr)
300
31 8
337
357
377
399
422
553
925
1494
2337
3551
5258
7600
gas equation (Equation 1 1-3) can be rearranged to give
P l V l
-~
' i
= nR = constant
In this problem, however, we must use the actual partial pressure of the O 2 in the
flask, not the total pressure. The partial pressure of O 2 is easily obtained by
subtracting the vapor pressure of H 2 O at 25°C (24 torr, from Table 11-1) from the
total pressure (730 torr) to give 706 torr. Therefore
_ (706 torr)(250 ml)(273 K)
2 ~
(760 torr)(298 K)
= 213 ml at standard conditions
PROBLEM:
What is the volume of one mole of N 2 (or««v gas) measured over water at 730 torr
and 30°C'
SOLUTION:
From Table 11-1, we find that the partial pressure of water vapor is 32 torr at 30°C.
Thus, the partial pressure of the N 2 is 730 torr - 32 torr = 698 torr. Applying the
ideal gas equation, we obtain