Dougherty Valley HS Chemistry
Dalton’s Law of Partial Pressure Practice Problems
Name:
Date:
Period:
Directions: Using the Dalton’s Law of Partial pressures, complete the following calculations on a separate sheet of paper,
be sure to attach this sheet to your answers. Must show ALL WORK to receive credit.
Abbreviations
atm - atmosphere
mm Hg - millimeters of mercury
torr - another name for mm Hg
Pa - Pascal (kPa = kilo Pascal)
K - Kelvin
°C - degrees Celsius
Conversions
K = °C + 273
1 cm3 (cubic centimeter) = 1 mL (milliliter)
1 dm3 (cubic decimeter) = 1 L (liter) = 1000 mL
Standard Conditions
0.00 °C = 273 K
1.00 atm = 760.0 mm Hg = 101.325 kPa = 101,325 Pa
The vapor pressure of water in kilopascals is here. Remember to convert to mmHg or atm. as needed.
[1] A container holds three gases: oxygen, carbon dioxide, and helium. The partial pressures of the three
gases are 2.00 atm, 3.00 atm, and 4.00 atm, respectively. What is the total pressure inside the container? 9.00
atm.
[2] A container with two gases, helium and argon, is 30.0% by volume helium. Calculate the partial pressure of
helium and argon if the total pressure inside the container is 4.00 atm. 2.8 atm
[3] If 60.0 L of nitrogen is collected over water at 40.0 °C when the atmospheric pressure is 760.0 mm Hg,
what is the partial pressure of the nitrogen? 705 mmHg
[4] 80.0 liters of oxygen is collected over water at 50.0 °C. The atmospheric pressure in the room is 96.00 kPa.
What is the partial pressure of the oxygen? 83.7 kPa
[5] A tank contains 480.0 grams of oxygen and 80.00 grams of helium at a total pressure of 7.00 atmospheres.
Calculate the following.
a) How many moles of O2 are in the tank? 15 mol
b) How many moles of He are in the tank? 20 mol
c) Total moles of gas in tank. 35 mol
d) Mole fraction of O2. Skip
e) Mole fraction of He. Skip
f) Partial pressure of O2. 3.0002 atm
g) Partial pressure of He. 3.9998 atm
[6] A tank contains 5.00 moles of O2, 3.00 moles of neon, 6.00 moles of H2S, and 4.00 moles of argon at a total
pressure of 1620.0 mm Hg. Complete the following table
Moles
O2
5
Ne
3
H2S
6
Ar
4
Mole fraction
Pressure fraction
Partial Pressure
Total
18.00
1
0.287
0.167
0.333
0.222
1
1620.0
[7] A mixture of 14.0 grams of hydrogen, 84.0 grams of nitrogen, and 2.0 moles of oxygen are placed in a flask.
When the partial pressure of the oxygen is 78.00 mm of mercury, what is the total pressure in the flask? 468
mmHg
[8] A flask contains 2.00 moles of nitrogen and 2.00 moles of helium. How many grams of argon must be
pumped into the flask in order to make the partial pressure of argon twice that of helium?
Vapor Pressure Data for H2O
If you need to convert to atmospheres, divide by 101.325.
If you need to convert to millimeters of mercury, divide by 101.325, then multiply by 760.0
Click if you need to interpolate between whole degrees. - Below
Temperature
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
kPa
0.61129
0.65716
0.70605
0.75813
0.81359
0.8726
0.93537
1.0021
1.073
1.1482
1.2281
1.3129
1.4027
1.4979
1.5988
1.7056
1.8185
1.938
2.0644
2.1978
2.3388
2.4877
2.6447
2.8104
2.985
3.169
3.3629
3.567
3.7818
4.0078
4.2455
4.4953
4.7578
5.0335
5.3229
5.6267
5.9453
6.2795
6.6398
6.9969
7.3814
7.784
8.2054
8.6463
9.1075
9.5895
10.094
10.62
11.171
11.745
Temperature
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
kPa
12.344
12.97
13.623
14.303
15.012
15.752
16.522
17.324
18.159
19.028
19.932
20.873
21.851
22.868
23.925
25.022
26.163
27.347
28.576
29.852
31.176
32.549
33.972
35.448
36.978
38.563
40.205
41.905
43.665
45.487
47.373
49.324
51.342
53.428
55.585
57.815
60.119
62.499
64.958
67.496
70.117
72.823
75.614
78.494
81.465
84.529
87.688
90.945
94.301
97.759
Source: Handbook of Chemistry and Physics: 73rd Edition (1992-93)
Interpolation
Suppose you need to determine the vapor pressure of water at 25.4°C.
You know that at 24.0°C the vapor pressure is 2.985 kPa and at 25.0°C it is 3.169 kPa.
First, determine the difference between the two pressures: 3.169 - 2.985 = 0.184 kPa.
Second, multiply the difference by the decimal portion (ONLY!) of the desired temperature: 0.184 x 0.4 =
0.0736 kPa.
Third, add this value to the LOWER pressure you used in the first step: 2.985 + 0.0736 = 3.0586 kPa.
Last, round off to the appropriate number of significant figures. In this case, the answer would be 3.059
kPa