Deck 6: Properties of Gases: the Air We Breathe

Question 1

What pressure (in Pa) will be exerted on the bottom of a 63.5 kg hiker's foot when she stands on a rusty nail? Assume the diameter of the tip of the nail is 1.00 mm. The acceleration due to gravity is 9.81 m/s². Recall that the area of a circle is: A = $\pi$ r² and that 1 Pa = 1 kg m^-1 s^-2.

A) 1.98 * 10² Pa
B) 7.93 * 10² Pa
C) 1.98 * 10⁸ Pa
D) 7.93 *10⁸ Pa
E) 7.93 *10⁵ Pa

Answer 1

7.93 *10⁸ Pa

Question 2

A soft drink rises in a straw when you suck on the straw because ________

A) the vacuum pulls the liquid up the straw.
B) capillary forces attract the liquid to the walls of the straw.
C) the air pressure inside the straw is less than the air pressure outside the straw.
D) the air pressure inside the straw is greater than the air pressure outside the straw.
E) the liquid level inside the straw is pushed up by the liquid level outside the straw.

Answer 2

the air pressure inside the straw is less than the air pressure outside the straw.

Question 3

What force is exerted by exactly one atmosphere of pressure (1.013 *10⁵ Pa) on a mercury barometer with an inner diameter of 20.00 mm?
Recall that the area of a circle is A = $\pi$ r² and that 1 N = 1 kg m/s².

A) 31.82 N
B) 15.91 N
C) 127.3 N
D) 3.182 * 10⁷ N
E) 40.52 N

Answer 3

31.82 N

Question 4

The atmospheric pressure is reported to be 31.5 in of mercury. The prevailing weather system on this day would be classified as ________

A) a cold front.
B) a warm front.
C) low pressure.
D) high pressure.
E) normal.

Question 5

Two identical cement blocks are placed on a glass table in different positions as shown in the diagram. Which statement about these blocks is correct?

A) A exerts more pressure on the table.
B) B exerts more pressure on the table.
C) Both blocks exert the same pressure on the table.
D) A exerts more force on the table.
E) B exerts more force on the table.

Question 6

The cold inflation pressure of many car tires is 30 lb/in², which is the gauge pressure. If
1 atm = 14.7 lb/in², what is the gauge pressure of a car tire in torr?

A) 2.04 torr
B) 1.55 * 10³ torr
C) 441 torr
D) 0.580 torr
E) 1.12* 10⁴ torr

Question 7

What pressure will be measured (in Pa) if a gas is exerting a force of 10.00 N on a mercury barometer with an inner diameter of 10.00 mm?
Recall that the area of a circle is A = $\pi$ r² and that 1 N = 1 kg m/s².

A) 3.183 * 10⁴ Pa
B) 1.273 * 10⁵ Pa
C) 3.183 *10^-2 Pa
D) 1.273*10^-2 Pa

Question 8

Which statement about the properties of a gas is not correct?

A) Unlike a solid or a liquid, gases expand to occupy the entire volume of their container.
B) When the temperature is changed, the volume of gas changes much more than the volume of a solid or liquid.
C) Different gases are completely miscible with each other.
D) The density of a gas typically is much larger than the density of a solid or liquid.
E) When the pressure is changed, the volume of a gas changes much more than the volume of a solid or liquid.

Question 9

What is the pressure in the gas bulb connected to the mercury manometer shown in the diagram if the ambient pressure is 750 torr? The heights labeled in the diagram are 15 mm and 21 mm.

A) 756 torr
B) 771 torr
C) 729 torr
D) 765 torr
E) 735 torr

Question 10

A gas is contained in the piston assembly and allowed to expand as in the following figure. Which point on the graph shows the correct final pressure and volume?

A) a
B) b
C) c
D) d

Question 11

Which of the following substances will require the highest column for measuring an atmospheric pressure of 0.950 atm? (Assume all the barometers have columns with the same diameter.)

A) Mercury (d = 13.59 g/cm³)
B) Ethanol (d = 0.79 g/cm³)
C) Ethylene glycol (d = 1.09 g/cm³)
D) Water (d = 1.00 g/cm³)
E) Carbon tetrachloride (d = 1.58 g/cm³)

Question 12

The pressure of a gas is inversely proportional to ________

A) the volume of the gas.
B) the number of gas particles.
C) the temperature of the gas.
D) the molar mass of the gas.
E) the mass of the gas.

Question 13

If the pressure in the eye of a hurricane is 645 mbar, what is the corresponding pressure in
Mm Hg? Recall 1.013 bar = 1 atm.

A) 637 mm Hg
B) 0.637 mm Hg
C) 484 mm Hg
D) 497 mm Hg
E) 645 mm Hg

Question 14

The composition of Earth's atmosphere by volume is ________ nitrogen, ________ oxygen, 0.93% argon, 0.039% carbon dioxide, around 1% water vapor, and small amounts of other gases.

A) 78%; 21%
B) 68%; 31%
C) 88%; 11%
D) 49%; 49%
E) 22%; 77%

Question 15

What height of water (in meters) is necessary to measure a pressure of 760 mm Hg? The density of mercury is 13.79 g/cm³, and the density of water is 1.00 g/cm³.

A) 0.760 m
B) 1.05 * 10⁴ m
C) 0.105 m
D) 10.5 m
E) 55.1 mm

Question 16

A 1.25 L bottle of soda exerts a force of ________ N and a pressure of ________ Pa when placed on a table. The round cylindrical bottle has a diameter of 10.0 cm and a height of 25.0 cm. Assume that the density of the soda is 1.0 g/mL, and that the mass of the plastic bottle is negligible. Remember, the acceleration due to gravity is 9.81 m/s²; 1 Newton = 1 kg m/s²,
1 Pascal = 1 kg/(m s²), A = $\pi$ r², V = $\pi$ r²h.

A) 9.8 N; 1200 Pa
B) 12 N; 390 Pa
C) 12 N; 16 Pa
D) 12 N; 12 Pa
E) 12 N; 1600 Pa

Question 17

Which of the following graphs shows the correct relationship between pressure and volume for n moles of gas at temperature T?

A)
B)
C)
D)

Question 18

The atmospheric pressure in the eye of a hurricane is found to be 26.6 in of mercury. The pressure in the eye of this hurricane is ________

A) 760 mm Hg.
B) 1.00* 10⁵ Pa.
C) 0.889 atm.
D) 0.987 bar.
E) 0.785 atm.

Question 19

The SI unit of force is the Newton (N), and the unit of pressure is the Pascal (Pa). In SI base units,
1 N = 1 kg m s^-2, and 1 Pa = ________.

A) 1 kg m^-1 s^-2
B) 1 kg m²s^-2
C) 1 kg m^-1 s^-1
D) 1 kg m^-2 s^-2
E) 1 kg s^-2

Question 20

A barometer measures a pressure of 745 mm Hg. What is this pressure in atm?

A) 0.980 atm
B) 1.02 atm
C) 1.03 *10⁵ atm
D) 1.00 * 10⁴ atm
E) 0.556 atm

Question 21

Four containers, each with the same volume and at the same temperature, are shown in the following diagrams. Which container is at the highest pressure?

A)
B)
C)
D)

Question 22

Which of the following graphs shows the correct relationship between the pressure and temperature of an ideal gas in a given volume? Note the origin corresponds to P = 0 atm and T = 0 K.

A)
B)
C)
D)

Question 23

A 22.4-L sealed chamber at 273 K is filled with air at a pressure of 1.00 atm. A solid state chemical reaction in the chamber adds 1.25 mol hydrogen gas. The temperature of the chamber must be decreased to ________ to maintain the pressure at 1.00 atm.

A) 121 K
B) 218 K
C) 12.2 K
D) 182 K
E) 211 K

Question 24

What volume is occupied by 1.00 mol of an ideal gas at 1.00 atm and 0.00°C?

A) 22.4 L
B) 22.7 L
C) 22.1 L
D) 15.0 L
E) 27.2 L

Question 25

An unknown gas held in a 25.0 mL flask at 45°F exerts a pressure of 25 mTorr. Using this information with the ideal gas law, it is possible to determine ________

A) the mass of the gas in the container.
B) the identity of the gas in the container.
C) the number of molecules of the gas in the container.
D) the molecular geometry of the gas in the container.
E) nothing more about the gas.

Question 26

Which of the following graphs shows the correct relationship between the temperature and volume of an ideal gas at a given pressure? Note the origin corresponds to V = 0 and T = 0.

A)
B)
C)
D)

Question 27

A balloon vendor at a street fair is using a tank of helium to inflate the balloons. The tank has a volume of 75 L and a pressure of 95 atm at 22°C. The valve is not closed completely and some helium leaks out. After some time, the pressure drops to 85 atm. How many moles of helium have been lost?

A) 0.90 mol
B) 1.2 mol
C) 73 mol
D) 263 mol
E) 31 mol

Question 28

A sample of gas at 4.0 atm and 25.0 mL is heated from 25°C to 40°C. If the pressure remains constant, what is the final volume of the gas?

A) 26.2 mL
B) 40.0 mL
C) 23.8 mL
D) 105 mL
E) 25.0 mL

Question 29

What is the volume of a gas that exerts a pressure of 457 mm Hg if it exerted a pressure of 2.50 atm when its volume was 25.0 mL?

A) 9.62 mL
B) 1.80 L
C) 0.104 L
D) 6.01 mL
E) 25.0 L

Question 30

A balloon is filled with 3.00 L of helium at a pressure of 765 torr. What is the volume of the balloon at an altitude where the pressure in the balloon is 530 torr?

A) 0.231 L
B) 4.33 L
C) 2.08 L
D) 1.00 L
E) 3.00 L

Question 31

How many moles of propane are contained in a 5.00 L tank at 450 torr and 25°C?

A) 0.12 mol
B) 92 mol
C) 1.4 mol
D) 1,100 mol
E) 41 mol

Question 32

Which of the following is unimportant when using the ideal gas law?

A) The chemical identity of the gas sample.
B) The temperature of the gas sample.
C) The pressure of the gas sample.
D) The volume of the container holding the gas sample.
E) The amount of gas.

Question 33

In an experiment, 7.5 mol of a gas are held in a 3.5 L container at 39°C. What pressure does the gas exert if it is assumed to be ideal?

A) 5.5 * 10³ atm
B) 2.9*10⁴ atm
C) 6.9 atm
D) 55 atm
E) 96 atm

Question 34

A gas, initially at 1.00 atm and 5.00 L, is compressed to a pressure of 15.00 atm. What is the volume of the gas at this pressure?

A) 3.00 L
B) 333 mL
C) 0.333 mL
D) 3.00 mL
E) 5.00 L

Question 35

What is the pressure of a 3.5 mmol sample of ethane (C₂H₆) gas contained in a 0.500 L flask at 298 K?

A) 171 mm Hg
B) 1.30* 10⁵ mm Hg
C) 130 mm Hg
D) 326 mm Hg
E) 17.1 mm Hg

Question 36

Which statement A-D regarding an ideal gas is not correct?

A) The volume occupied by an individual molecule is negligible.
B) No interactions occur between molecules other than hard sphere collisions.
C) Molecules move in random directions and collide with each other.
D) The volume occupied by 1 mol of molecules at STP is 22.4 L.
E) Statements A-D all are correct.

Question 37

A 1.50 mol sample of He occupies a volume of 2.50 L at a pressure of 14.7 atm. What will be the pressure of a 1.50 mol sample of H₂ gas under the same conditions?

A) 7.33 atm
B) 14.7 atm
C) 29.4 atm
D) 1.00 atm
E) 24.5 atm

Question 38

What volume is occupied by 1.00 mol of an ideal gas at 1.00 bar and 0.00°C?

A) 22.4 L
B) 22.7 L
C) 22.1 L
D) 15.0 L
E) 27.2 L

Question 39

A 25.0 L balloon is filled with 2.75 mol of helium. If the helium leaks out at the rate of 0.105 mol/hr, what is the volume of the balloon after 12.0 hr? Assume the pressure and temperature don't change.

A) 11.5 L
B) 13.5 L
C) 23.7 L
D) 1.26 L
E) 17.4 L

Question 40

Which of the gases shown here will exert the lowest pressure, assuming that each container has the same volume and temperature?

A)
B)
C)
D)

Question 41

What is the density of propane gas (CH₃CH₂CH₃, 44.1 g/mol) at 25°C and 650 mm Hg?

A) 1.54 g/L
B) 3.55 g/mL
C) 18.3 g/L
D) 2.05 g/L
E) 1.17 g/L

Question 42

Calcium carbonate (100.1 g/mol) decomposes according to the following reaction equation:
CaCO₃(s) $\rightarrow$ CaO(s) + CO₂(g)
What pressure of CO₂ gas will form in a 25.0 mL jar containing 5.00 g CaCO₃ at 300 K if 0.00500% of the solid decomposes?

A) 0.246 atm
B) 2.46 atm
C) 1.00 atm
D) 2.46 *10³ atm
E) 2.46 *10^-3 atm

Question 43

Which of the gas samples shown below in identical containers has the lowest density (g/L)?

A)
B)
C)
D)

Question 44

The pressure gauge on a 100-L cylinder used to fill balloons with helium shows a pressure of 1,470 psi at a temperature of 22^oC. How many kilograms of helium does the cylinder contain?

A) 6.04 kg
B) 1.65 kg
C) 0.779 kg
D) 4.30 kg
E) 0.464 kg

Question 45

Indicate the gas with the greatest density at STP.

A) CH₄
B) He
C) Ar
D) H₂
E) O₂

Question 46

Poisonous carbon monoxide can be produced by furnaces in basements if the combustion and exhaust are not complete. Calculate the density of carbon monoxide in g/L at 292 K and 1.00 atm of pressure to determine whether it is more or less dense than air. If it is more dense, it will remain in the basement, if it is less dense it will rise to the upper levels of the house. The density of dry air is 1.20 g/L.

A) 1.14 g/L
B) 1.17 g/L
C) 1.20 g/L
D) 1.23 g/L
E) 1.26 g/L

Question 47

Which of the following samples of an ideal gas has the lowest density?

A)
B)
C)
D)

Question 48

Which of the following graphs shows how the density of an ideal gas changes with temperature?

A)
B)
C)
D)

Question 49

Which of the following gases has nearly the same density as CO₂ at room temperature and atmospheric pressure?

A) N₂
B) O₂
C) N₂O
D) Ar
E) CO

Question 50

The density of a pure gas at STP depends on its ________

A) molar mass.
B) concentration.
C) temperature.
D) volume.
E) pressure.

Question 51

Which one of these samples contains the smallest number of molecules?

A) 1.0 L of H₂ at STP (0°C and 1atm)
B) 1.0 L of N₂ at STP
C) 1.0 L of H₂ at 20°C and 760 torr
D) 1.0 L of N₂ at 0°C and 800 torr
E) 1.0 L of He at STP

Question 52

In an experiment, 25.0 mL of a gas with a pressure of 1.00 atm is contained in a balloon at 25.0°C. The balloon is then cooled to 5.0°C, and the pressure is found to be 0.750 atm. What is the volume of the gas under the new conditions?

A) 17.5 mL
B) 20.1 mL
C) 25.0 mL
D) 31.1 mL
E) 35.7 mL

Question 53

Which of the following reactions will result in a reduced total pressure?

A) CH₄(g) + 2O₂(g) $\rightarrow$ CO₂(g) + 2H₂O(g)
B) 2N₂O(g) $\rightarrow$ 2N₂(g) + O₂(g)
C) 2HI(g) $\rightarrow$ H₂(g) + I₂(g)
D) 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(l)

Question 54

The pressure gauge on a cylinder used to fill balloons with He shows a pressure of 1,275 psi at a temperature of 25°C. Assuming the cylinder has a volume of 10 L, how many grams of He does the cylinder contain?

A) 520 g
B) 142 g
C) 6.70 *10^-4 g
D) 37.0 g
E) 4.00 g

Question 55

Automobile airbags inflate during a crash due to the rapid generation of nitrogen gas from the decomposition of sodium azide.
2NaN₃(s) $\rightarrow$ 2Na(s) + 3N₂(g)
How many grams of sodium azide are needed to produce enough nitrogen gas to fill a 60 cm * 60 cm * 30 cm air bag to a pressure of 1.25 atm at a temperature of 20^oC?

A) 157 g
B) 243 g
C) 365 g
D) 548 g
E) 65.7 g

Question 56

Which one of the following gases could most easily be differentiated from propane (CH₃CH₂CH₃) on the basis of density when compared at the same temperature and pressure?

A) CO₂
B) N₂O
C) NO₂
D) F₂
E) CH₂
CH-CH₃

Question 57

Considering that PV = nRT, which one of these samples contains the largest number of particles? STP = 0°C and 1 atm.

A) 2.0 L of H₂ at STP
B) 2.0 L of N₂ at STP
C) 2.0 L of H₂ at 25°C and 760 torr
D) 2.0 L of N₂ at 0°C and 900 torr
E) 2.0 L of He at STP

Question 58

Automobile air bags inflate during a crash or sudden stop by the rapid generation of nitrogen gas from sodium azide.
2NaN₃(s) $\rightarrow$ 2Na(s) + 3N₂(g)
How many moles of sodium azide are needed to produce sufficient nitrogen to fill a 50.0 L air bag to a pressure of 1.25 atm at 25°C?

A) 2.56 mol
B) 3.83 mol
C) 5.31 mol
D) 1.70 mol
E) 4.92 mol

Question 59

What is the temperature if 5.0 g of methane (CH₄) in a 100.0 mL container exerts a pressure of 42 atm?

A) -110°C
B) +164°C
C) -270°C
D) -263°C
E) +263°C

Question 60

Considering that PV = nRT, which one of these samples contains the smallest number of particles? STP = 0°C and 1 atm.

A) 2.0 L of H₂ at STP
B) 2.0 L of N₂ at STP
C) 2.0 L of H₂ at 25°C and 760 torr
D) 2.0 L of N₂ at 0°C and 900 torr
E) 2.0 L of He at STP

Question 61

The density of a gaseous compound of nitrogen and oxygen is 4.11 g/L at STP. What is the most likely formula of this gas?

A) N₂O₄
B) N₂O₅
C) N₂O
D) NO₂
E) NO

Question 62

In which of the following containers is the mole fraction of helium greatest? The white circles represent helium atoms; the dark circles represent argon atoms.

A)
B)
C)
D)

Question 63

When a certain acid and a certain base are mixed together, a reaction occurs that produces a gas as one of the products. The gas has a density of 2.62 g/L at 1.00 atm and 25°C. What is the molar mass and identity of the gas?

A) H₂, 2 g/mol
B) CO, 28 g/mol
C) O₂, 32 g/mol
D) CO₂, 44 g/mol
E) SO₂, 64 g/mol

Question 64

Dry air consists of 78.1% nitrogen (28 g/mol), 20.9% oxygen (32 g/mol), 0.9% argon (40 g/mol), 0.03% carbon dioxide (44 g/mol), and 0.07% other gases by volume. Which gas has the largest mole fraction in the composition of air?

A) nitrogen
B) oxygen
C) argon
D) carbon dioxide
E) the total of the other gases

Question 65

When a certain acid and a certain base are mixed together, a reaction occurs that produces a gas as one of the products. The gas has a density of 1.83 g/L at 1.00 atm and 20°C. What is the molar mass and identity of the gas?

A) H₂, 2 g/mol
B) CO, 28 g/mol
C) O₂, 32 g/mol
D) CO₂, 44 g/mol
E) SO₂, 64 g/mol

Question 66

In which of the following containers is the mole fraction of argon greatest? The white circles represent helium atoms; the dark circles represent argon atoms.

A)
B)
C)
D)

Question 67

Dry air consists of 78.1% nitrogen (28 g/mol), 20.9% oxygen (32 g/mol), 0.9% argon (40 g/mol), 0.03% carbon dioxide (44 g/mol), and 0.07% other gases by volume. What is the partial pressure of oxygen in air when the total pressure is 760 torr?

A) 594 torr
B) 159 torr
C) 94 torr
D) 59 torr
E) 236 torr

Question 68

Which container shown below has the largest partial pressure of argon? The white circles represent helium atoms; the dark circles represent argon atoms.

A)
B)
C)
D)

Question 69

Which container shown below has the largest partial pressure of helium? The white circles represent helium atoms; the dark circles represent argon atoms.

A)
B)
C)
D)

Question 70

A gas mixture has partial pressures of 120 torr N₂, 350 torr Ar, and 480 torr SF₆. What is the mole fraction of sulfur hexafluoride in the mixture?

A) 0.13
B) 0.37
C) 0.45
D) 0.51
E) 0.55

Question 71

Nitrous oxide (N₂O, also known as laughing gas) has been used as an anesthetic. What is the density of N₂O at 750 torr and 30°C?

A) 1.2 g/L
B) 1.1 g/L
C) 1.9 g/L
D) 1.7 g/L
E) 1.5 g/L

Question 72

In a mixture of hydrogen and helium gases, the mole fraction of helium is 0.750. If the partial pressure of hydrogen in the mixture is 75 torr, what is the total pressure of the mixture?

A) 100 torr
B) 300 torr
C) 19 torr
D) 750 torr
E) 760 torr

Question 73

Which of the containers shown below has the lowest total pressure? The white circles represent helium atoms; the dark circles represent argon atoms.

A)
B)
C)
D)

Question 74

The partial pressure of a gas is ________

A) the pressure the gas exerts when pure.
B) the same as the vapor pressure of the gas.
C) the pressure due to the gas in a mixture.
D) the total pressure of a mixture of gases.
E) the pressure exerted by one molecule of the gas.

Question 75

When a certain acid and a certain base are mixed together, a reaction occurs that produces a gas as one of the products. The gas has a density of 2.62 g/L at 1.47 atm and 27°C. What is the molar mass and identity of the gas?

A) H₂, 2 g/mol
B) CO, 28 g/mol
C) O₂, 32 g/mol
D) CO₂, 44 g/mol
E) SO₂, 64 g/mol

Question 76

In a mixture of gases, the gas with the largest mole fraction will have the ________

A) largest molar mass.
B) smallest molar mass.
C) largest number of molecules present.
D) smallest number of molecules present.
E) highest kinetic energy.

Question 77

The density of an unknown gas is 1.72 g/L at 750.0 torr and 30.0°C. Which of the following could be the unknown gas?

A) CS₂
B) NO
C) N₂O
D) NH₃
E) NO₂

Question 78

What is the molar mass of a gas that has a density of 2.62 g/L at 2.00 atm and 25.0°C?

A) 32.0 g/mol
B) 16.0 g/mol
C) 64.0 g/mol
D) 28.0 g/mol
E) 2.69 g/mol

Question 79

What is the mole fraction of H₂ in a mixture with a total pressure of 800 torr when the partial pressure of H₂ is 90 torr?

A) 0.11
B) 8.8
C) 1.0
D) 0.5
E) 0.88

Question 80

N₂O (laughing gas) is used as an anesthetic. A dentist has a 2.00 L flask of N₂O at a pressure of 1.00 atm and a 3.00 L flask of nitrogen gas at 2.00 atm that are separated by a valve. What is the pressure in the flasks when the valve is opened, and the gases mix together? Both flasks are at the same temperature, and the temperature does not change when the gases mix.

A) 3.00 atm
B) 1.50 atm
C) 1.60 atm
D) 1.20 atm
E) 1.00 atm