AP Gases Review

A mixture of gases at 810 kPa pressure contains:

3.0 moles of oxygen gas,

2.0 moles of helium gas, and

4.0 moles of carbon dioxide gas.

What is the partial pressure of helium gas (P_He)?

• 165 kPa

• 180 kPa

• 135 kPa

• 200 kPa

• 250 kPa

A sample of gas occupies 30.0 L at 0.800 atm and 298 K. How many moles of gas are in the sample?

• 1.02 mol

• 0.852 mol

• 0.981 mol

• 1.27 mol

• none of the above

At STP, it was found that 1.12 L of a gas had a mass of 2.78 g. Its molar mass is

• 55.6 g/mol

• 27.8 g/mol

• 36.9 g/mol

• 39.2 g/mol

• 45.8 g/mol

A mixture of gases, nitrogen, oxygen, and carbon dioxide at 27 C and 0.50 atm pressure occupied a volume of 492 mL. The partial pressure of oxygen is 0.15 atm, what is the mole fraction of oxygen in the sample?

• 0.85

• 0.23

• 0.49

• 0.16

• 0.30

What is the pressure exerted by some nitrogen gas collected in a tube filled with water on a day when the room temperature is 18.0 °C and the room pressure is 750.0 mmHg? [The partial pressure of water at 18 °C is 15.5 mmHg.]

• 765.5 mmHg

• 750.0 mmHg

• 734.5 mmHg

• 760.0 mmHg

• 745.5 mmHg

16 grams of oxygen, 8 grams of hydrogen, and 32 grams of sulfur dioxide are placed together in a vessel. The total pressure exerted by the mixture of gases if 756 torr. The partial pressure exerted by the oxygen is:

• 75.6 torr

• 216 torr

• 252 torr

• 85.4 torr

• 207 torr

Calculate the molar mass of an ideal gas which has a density of 1.87 g/L at 30°C and a pressure of 0.98 atm.

• 31.2 g/mol

• 38.3 g/mol

• 47.4 g/mol

• 43.9 g/mol

• 40.2 g/mol

A 320 cm³ sample of a mixture of oxygen gas saturated with water vapor at 22°C exerts a total pressure of 748 torr. At 22°C the vapor pressure of water is 20 torr. Calculate the number of grams of oxygen in the sample.

• 0.416 g

• 0.405 g

• 0.203 g

• 0.472 g

• 0.308 g

If 6.6 g of a gaseous compound occupies a volume of 1.2 L at 27°C and 0.967 atm, the molar mass of the compound is

• 163 g/mol

• 129 g/mol

• 137 g/mol

• 140 g/mol

• 154 g/mol

How many times faster does a sample of helium gas effuse compared to oxygen gas?

• 8

• 4.29

• 2.82

• 3.89

• 4.48