65. 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?  65. 9.00 atm. 
66. 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.  66. P_{He} = 0.300 x 4.00 atm = 1.20 atm. P_{Ar} = 4.00  1.20 
67. 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?  67. 760.0 mmHg minus 55.3 mmHg 
68. 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?  68. 96.00 kPa minus 12.33 kPa 
69. 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 O_{2} are in the tank? b) How many moles of He are in the tank? c) Total moles of gas in tank. d) Mole fraction of O_{2}. e) Mole fraction of He. f) Partial pressure of O_{2}. g) Partial pressure of He.
 69.a) 480.0 g O_{2} / 32.0 g/mol b) 80.00 g He / 4.00 g/mol c) 35.0 moles d) 15.0 mol O_{2} / 35.0 mol e) 20.0 mol He / 35.0 mol f) 7.00 atm x 0.4286 g) 7.00 atm x 0.5714
Keep in mind that once one partial pressure is calculated, the other can be arrived at by subtraction, if so desired. 
70. A tank contains 5.00 moles of O_{2}, 3.00 moles of neon, 6.00 moles of H_{2}S, and 4.00 moles of argon at a total pressure of 1620.0 mm Hg. Complete the following table
O_{2} Ne H_{2}S Ar Total
Moles 18.00
Mole fraction 1
Pressure fraction 1
Partial Pressure 1620.0  70. Complete the following table  O_{2}  Ne  H_{2}S  Ar  Total  Moles  5.00  3.00  6.00  9.00  18.00  Mole fraction  5/18 = 0.278  3/18 = 0.167  6/18 = 0.333  4/18 = 0.222  1  Pressure fraction  0.278  0.167  0.333  0.222  1  Partial Pressure  1620 x 0.278 = 450.36  1620 x 0.167 = 270.54  1620 x 0.0.333 = 539.46  1620 x 0.222 = 359.64  1620.0 

71. 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?  71. (14.0 g / 2.00 g/mol) + (84.0 g /28.0 g/mol) + (2.0 moles) = 12.0 moles total 2.0/ 12.0 = 0.167 of the total pressure. 78.00 is to 0.167 as the total pressure is to one, so 468 mmHg is the answer. 
72. 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?  72. 4.00 moles 