Deck 18: Kinetic Theory of Gases

Question 1

When comparing two gases at the same temperature, the molecules of the gas with the smaller molecular weight have the higher rms speed.

Answer 1

True

Question 2

When a liquid freezes

A)the temperature of the substance increases.
B)the temperature of the substance decreases.
C)heat energy leaves the substance.
D)heat energy enters the substance.

Answer 2

heat energy leaves the substance.

Question 3

What is the Maxwell distribution?

Answer 3

The Maxwell distribution describes the likelihood that a molecule of gas will have a certain speed.

Question 4

When a vapor condenses

A)the temperature of the substance increases.
B)the temperature of the substance decreases.
C)heat energy leaves the substance.
D)heat energy enters the substance.

Question 5

The three phases of matter can exist together in equilibrium at the

A)critical point.
B)triple point.
C)melting point.
D)boiling point.
E)evaporation point.

Question 6

Which of the following best explains why sweating is important to humans in maintaining suitable body temperature?

A)Functioning of the sweat gland absorbs energy that otherwise would go into heating the body.
B)The high specific heat of water on the skin absorbs heat from the body.
C)Evaporation of moisture from the skin extracts heat from the body.
D)Moisture on the skin increases thermal conductivity, thereby allowing heat to flow out of the body more effectively.
E)None of the other choices is correct.

Question 7

The point in the phase diagram where the fusion curve, the vapor pressure curve, and the sublimation curve join is called the

A)critical point.
B)triple point.
C)melting point.
D)boiling point.
E)double point.

Question 8

A sample of an ideal gas is slowly compressed to one-half its original volume with no change in temperature. What happens to the average speed of the molecules in the sample?

A)It does not change.
B)It quadruples.
C)It doubles.
D)It halves.
E)none of the above

Question 9

The point in the phase diagram where the vapor pressure curve ends is called the

A)critical point.
B)triple point.
C)melting point.
D)boiling point.
E)double point.

Question 10

Phase changes occur

A)as the temperature decreases.
B)as the temperature increases.
C)as the temperature remains the same.
D)all of the above
E)none of the above

Question 11

What would be the greatest effect of the finite size of molecules on the ideal gas law?

A)At low densities, the pressure would be less than that predicted by the ideal gas law.
B)At high densities, the pressure would be less than that predicted by the ideal gas law.
C)At high densities, the pressure would be greater than that predicted by the ideal gas law.
D)At low densities, the pressure would be higher than that predicted by the ideal gas law.
E)There is no effect.

Question 12

In a cloud formation, water vapor condenses into water droplets which get bigger and bigger until it rains. This will cause the temperature of the air in the clouds to

A)increase.
B)decrease.
C)stay constant.
D)freeze.

Question 13

What would be the greatest effect on the ideal gas law if there is a slight repulsive force between the molecules?

A)At low temperatures, the pressure would be greater than that predicted by the ideal gas law.
B)At high temperatures, the pressure would be greater than that predicted by the ideal gas law.
C)At low temperatures, the pressure would be less than that predicted by the ideal gas law.
D)At high temperatures, the pressure would be less than that predicted by the ideal gas law.
E)There is no effect.

Question 14

When a liquid evaporates

A)the temperature of the substance increases.
B)the temperature of the substance decreases.
C)heat energy leaves the substance.
D)heat energy enters the substance.

Question 15

A liquid boils when its vapor pressure

A)equals the equilibrium vapor pressure.
B)equals the external pressure.
C)exceeds the external pressure.
D)is between the equilibrium vapor pressure and the external pressure.
E)None of the other choices is correct.

Question 16

A container is filled with a mixture of helium and oxygen gases. A thermometer in the container indicates that the temperature is 22°C. Which gas molecules have the greater average kinetic energy?

A)It is the same for both because the temperatures are the same.
B)The oxygen molecules do because they are diatomic.
C)The oxygen molecules do because they are more massive.
D)The helium molecules do because they are less massive.
E)The helium molecules do because they are monatomic.

Question 17

A container is filled with a mixture of helium and oxygen gases. A thermometer in the container indicates that the temperature is 22°C. Which gas molecules have the greater average speed?

A)The helium molecules do because they are monatomic.
B)It is the same for both because the temperatures are the same.
C)The oxygen molecules do because they are diatomic.
D)The oxygen molecules do because they are more massive.
E)The helium molecules do because they are less massive.

Question 18

What would be the greatest effect on the ideal gas law if there is a slight attractive force between the molecules?

A)At low temperatures, the pressure would be less than that predicted by the ideal gas law.
B)At low temperatures, the pressure would be greater than that predicted by the ideal gas law.
C)At high temperatures, the pressure would be greater than that predicted by the ideal gas law.
D)At high temperatures, the pressure would be less than that predicted by the ideal gas law.
E)There is no effect.

Question 19

The average molecular kinetic energy of a gas can be determined by knowing only

A)the number of molecules in the gas.
B)the volume of the gas.
C)the pressure of the gas.
D)the temperature of the gas.
E)all of the above must be known.

Question 20

When a solid melts

A)the temperature of the substance increases.
B)the temperature of the substance decreases.
C)heat energy leaves the substance.
D)heat energy enters the substance.

Question 21

Quito, Ecuador, is at an altitude of 2,850 meters above sea level, while New York City is at sea level. If you are preparing a hard-boiled egg in Quito, it would have to be placed in boiling water

A)for the same amount of time as in New York.
B)for a shorter time than in New York.
C)for a longer time than in New York.
D)There is not enough information to answer this question.

Question 22

What is the root mean square value of the following speeds: 2.0 m/s, 3.0 m/s, 4.0 m/s?

A)1.0 m/s
B)2.8 m/s
C)2.9 m/s
D)3.0 m/s
E)3.1 m/s

Question 23

The rms speed of the molecules of a gas is 200 m/s at a temperature 300 K. What is the mass of the individual molecules?

A)2.13 × 10^-25 kg
B)2.45 × 10^-25 kg
C)5.66 × 10^-25 kg
D)1.78 × 10^-25 kg
E)3.11 × 10^-25 kg

Question 24

What is the root mean square value of the following velocity components: 2.0 m/s, -3.0 m/s, and 4.0 m/s?

A)5.4 m/s
B)1.9 m/s
C)3.1 m/s
D)3.3 m/s
E)1.0 m/s

Question 25

What is the average kinetic energy of a nitrogen molecule in the air in a room in which the air temperature is 17.0°C?

A)6.01 × 10^-21 J
B)4.00 × 10^-21 J
C)5.00 × 10^-21 J
D)7.00 × 10^-21 J
E)9.00 × 10^-21 J

Question 26

A gas consists of particles of mass 3.00 × 10^-26 kg. What is the pressure in a gas of these particles if there are 2.00 × 10²⁵ particles per cubic meter of gas and the rms speed of the particles is 400 m/s?

A)1.01 × 10⁵ N/m²
B)1.60 × 10⁴ N/m²
C)9.60 × 10⁴ N/m²
D)4.80 × 10⁴ N/m²
E)3.20 × 10⁴ N/m²

Question 27

What is the average kinetic energy per molecule of an ideal gas at a temperature of 300 K? Boltzmann's constant is k = 1.38 × 10^-23 J/K.

A)1.7 × 10^-21 J
B)8.3 × 10^-21 J
C)6.2 × 10^-21 J
D)2.1 × 10^-21 J
E)4.1 × 10^-21 J

Question 28

The rms speed of the molecules of a gas is 200 m/s at a temperature 300 K. What is the rms speed of the molecules at 500 K?

A)155 m/s
B)333 m/s
C)258 m/s
D)556 m/s
E)800 m/s

Question 29

At what temperature is the rms speed of hydrogen molecules, which have a molecular weight of 2.02 g/mole, equal to 2000 m/s?

A)17.0°C
B)34.0°C
C)51.0°C
D)68.0°C
E)72.0°C

Question 30

What is the mean free path of a gas of hard spheres of radius 2.00 × 10^-9 m when the number of spheres per volume is 3.00 × 10¹⁹ m^-3?

A)1.17 × 10^-4 m
B)4.00 × 10^-9 m
C)9.76 × 10^-5 m
D)1.88 × 10^-3 m
E)4.69 × 10^-4 m

Question 31

For chlorine gas, the van der Waals constants are: a = 0.658 J∙m³/mol², and b = 5.62 × 10^-5 m³/mol. A 3.0-L tank contains 10.0 moles of chlorine gas at a temperature of 625 K. What is the pressure in the container?

A)14.0 MPa
B)13.5 MPa
C)17.3 MPa
D)11.0 MPa
E)18.2 MPa

Question 32

The rms speed of a certain sample of carbon dioxide molecules, with a molecular weight of 44 g/mole, is 396 m/s. What is the rms speed of water molecules, with a molecular weight of 18 g/mol, at the same temperature?

A)253 m/s
B)387 m/s
C)421 m/s
D)506 m/s
E)619 m/s

Question 33

A cubic box with sides of 20 cm contains 2 × 10²³ molecules of helium with a root-mean-square (rms) speed of 200 m/s. The mass of a helium molecule is 3.4 × 10^-27 kg. What is the average pressure exerted by the molecules on the walls of the container?

A)3.39 kPa
B)1.13 kPa
C)570 Pa
D)2.26 kPa
E)9.1 Pa

Question 34

For carbon dioxide, the van der Waals constants are: a = 0.364 J∙m³/mol², and b = 4.27 × 10^-5 m³/mol. Assuming that the van der Waals equation holds at the critical point (where the p-V curve first becomes horizontal and has a point of inflection), what is the critical temperature of carbon dioxide?

A)513 K
B)592 K
C)304 K
D)1026 K
E)326 K

Question 35

What is the mean free path of molecules in an ideal gas in which the mean collision time is 3.00 × 10^-10 s, the temperature is 300 K, and the mass of the molecules is 6.00 × 10^-25 kg?

A)7.22 × 10^-8 m
B)4.32 × 10^-8 m
C)9.19 × 10^-8 m
D)1.39 × 10^-8 m
E)6.71 × 10^-8 m

Question 36

What is the mean free path for the molecules in an ideal gas when the pressure is 100 kPa and the temperature is 300 K given that the collision cross-section for the molecules of that gas is 2.0 × 10^-20 m²? Boltzmann's constant is k = 1.38 × 10^-23 J/K.

A)1.1 × 10^-6 m
B)2.1 × 10^-6 m
C)1.7 × 10^-6 m
D)5.3 × 10^-6 m
E)1.5 × 10^-6 m

Question 37

La Paz, Bolivia, is at an altitude of 3,650 meters above sea level. In La Paz, water will boil

A)at 100°C.
B)below 100°C.
C)above 100°C.
D)There is not enough information to answer this question.