Deck 8: Gases

Question 1

A methane gas bubble forms on the floor of the ocean at a depth of 1000 m. Assume there is no exchange of heat or mass with the bubble's surroundings. By what fraction would the volume of the bubble increase by the time it breaks through the surface of the water at sea level?

A)9.8 × 10³
B)1 × 10⁶
C)9.8 × 10⁶
D)1 × 10⁷

Answer 1

9.8 × 10⁶

Question 2

Air enters the lungs at 15°C, and reaches the lungs at body temperature (37°C). Given that the tidal volume of the lungs is 0.5 L, what is the change in the energy of the air for each inhalation?

A)11.6 J
B)5.8 J
C)-5.8 J
D)-11.6 J

Answer 2

5.8 J

Question 3

Air in a room of dimensions 3 m × 4 m × 2 m is being heated by the Sun shining perpendicularly through a window of area 2 m², from a temperature of 10°C to 20°C in a time of 2 hours. Given that sunlight emits radiation with a total intensity of 1.361 kW/m², and assuming a pressure of 1 atm and that the mass of air in the room is constant, what fraction of this energy is absorbed by the air, thus warming up the room?

A)2.2 × 10^-3
B)3.3 × 10^-3
C)6.7 × 10^-3
D)1.1 × 10^-2

Answer 3

3.3 × 10^-3

Question 4

If molecules hitting the walls of a vessel did so inelastically instead of elastically, what pressure would one expect compared to the pressure caused by elastic collisions?

A)It would be the same.
B)It would decrease.
C)It would increase.
D)It is not possible to determine from the information given.

Question 5

Gas in a container with a volume of 1.50 L at a temperature of 0°C exerts a pressure of 2.00 atm. How many moles of gas are in the container?

A)0.13 moles
B)0.26 moles
C)1.30 moles
D)130 moles

Question 6

Which of these statements does NOT apply to isobaric change?

A)Density is proportional to temperature.
B)Volume is proportional to temperature.
C)Pressure is constant.
D)Density is inversely proportional to temperature.

Question 7

In Boyle's experiment, what determines the pressure in the volume of air in the sealed space?

A)the excess height of Hg between the two columns
B)the height of Hg in the open column
C)the excess height of Hg between the two columns, and the atmospheric pressure
D)the height of the air space in the sealed column

Question 8

The weight of a 1000 kg car is supported equally by four tires, which are inflated to the same gauge pressure. What gauge pressure is required so the area of contact of each tire with the road is 90 cm²?

A)27 kPa
B)28 kPa
C)272 kPa
D)280 kPa

Question 9

What is the ratio of the root-mean-square velocities of molecules of O₂ to water vapour molecules (of molar masses 32 and 18 respectively) in a gas in thermal equilibrium?

A)0.75
B)1.33
C)1.78
D)Cannot be determined with information given.

Question 10

Which one of the following properties does NOT describe an ideal gas?

A)A gas gives zero volume at a temperature of -273.15 K.
B)Mean energy per particle is proportional to absolute temperature.
C)Interactive forces between molecules are included.
D)The size of the molecules is neglected in comparison with their mean distance apart.

Question 11

Pressure in a gas is reduced by half, and the temperature is reduced to 80% of its initial value. What is the ratio of the final to the initial volume of the gas?

A)0.62
B)0.75
C)1.25
D)1.60

Question 12

Figure 8.1 Piston seals off a cylindrical container of oxygen.
In Fig. 8.1, a piston of cross-sectional area 1 m² seals a cylinder of gas, of length 0.5 m, at atmospheric pressure (so that there is no net force on the piston). The gas is at the ambient temperature of 20°C, then the gas is heated to 100°C. What extra force must the piston exert to contain the gas in the cylindrical space of reduced length 0.4 m?

A)3.0 × 10⁴ N
B)6.0 × 10⁴ N
C)1.2 × 10⁵ N
D)5.3 × 10⁵ N

Question 13

The gas in a constant-volume gas thermometer registers a pressure of 95.0 kPa at 100°C. Assume ideal behaviour. What is the temperature of this gas when the pressure is 250 kPa?

A)142°C
B)263°C
C)709°C
D)982°C

Question 14

Two gases, O₂ and CO₂, with molar masses of 32 g/mol and 44 g/mol respectively, are in a closed vessel separated by an impermeable membrane into two equal sub-volumes. If both the temperatures and the densities of each gas are the same, what is the ratio of the O₂ to CO₂ pressures exerted on the membrane?

A)0.7
B)1.0
C)1.4
D)2.8

Question 15

A cylindrical glass, closed at one end, of length 15 cm and cross-section 35 cm², is filled to a depth of 10 cm. A card is placed over the top and held there while the glass is inverted. What volume of water must leave the glass in order that the rest of the water should remain in the glass? Neglect the weight of the card.

A)0.85 × 10^-4 m³
B)1.74 × 10^-4 m³
C)2.19 × 10^-4 m³
D)3.48 × 10^-4 m³

Question 16

Figure 8.1 Piston seals off a cylindrical container of oxygen.
A certain gas in a closed container at 0.001 atm of pressure is irradiated with ionizing radiation, causing, on average, one electron to be stripped off each atom. The ionizing radiation also heats the gas from 20°C to 3000°C. The resulting ionized gas ("plasma") behaves like an ideal gas. What is the pressure in the plasma?

A)3.04 × 10⁵ Pa
B)4.92 × 10³ Pa
C)2.46 × 10³ Pa
D)1.23 × 10³ Pa

Question 17

In kinetic gas theory, which one of the following is an assumption and NOT a prediction of the theory?

A)Internal energy is proportional to absolute temperature.
B)The average speed of molecules depends only on absolute temperature.
C)The mean velocity of molecules is zero.
D)The product of pressure and volume of a gas is proportional to the number of molecules times their individual mean energy.

Question 18

Molybdenum melts at a temperature of 2623°C. What is the corresponding temperature on the Kelvin scale?

A)2350 K
B)2591 K
C)2723 K
D)2896 K

Question 19

A 15 m diameter spherical balloon is filled with air at a temperature of 60°C through a hole at the bottom of the balloon. Assume an outside atmospheric pressure of 1 atm and the average molecular mass of air is 29 g/mol. What is the mass of air contained within the balloon?

A)937 kg
B)1250 kg
C)1874 kg
D)3896 kg

Question 20

Figure 8.1 Piston seals off a cylindrical container of oxygen.
A 0.5 L bottle containing air at 30°C is sealed at sea level, where the atmospheric pressure is 1 atm. The bottle is re-opened at the top of a 2000-m-high mountain, where the pressure is 0.8 atm and the temperature is 0°C. What mass of air escapes the bottle, assuming that the air has a molar mass of 29 g/mol?

A)7.4 × 10^-5 kg
B)3.7 × 10^-4 kg
C)-7.4 × 10^-3 kg (that is, air enters the bottle)
D)7.4 × 10^-2 kg

Question 21

Mercury barometers measure atmospheric pressure by the height of a column of mercury in a sealed tube containing a vacuum. What effect does cross-sectional area have on the accuracy of measurements of pressure?

Question 22

In kinetic gas theory, we can predict the speed of an escaping particle.

Question 23

Describe why the compression ratio in a diesel engine must be higher than that in a gas engine.

Question 24

The mean speed of molecules escaping from the atmosphere of a planet into outer space is greater than the mean speed of molecules that remain in the atmosphere.

Question 25

In Dalton's law, the partial pressure of each component of a gas mixture is independent of temperature and total volume.

Question 26

All gases in Earth's atmosphere escape from it at equal rates.

Question 27

Dalton's law of partial pressures assumes that each component of a gas behaves as an ideal gas.

Question 28

A car weighing 1.2 × 10⁴ N rests on four tires. If the gauge pressure in each tire is 200 kPa, what is the area of each tire in contact with the road?

Question 29

A high voltage is applied across a sealed vessel containing gas at a very low pressure. If the voltage is high enough, electrons are stripped off the neutral atoms of gas (ionization), forming a current through the vessel. Some electrons recombine with positively charged ions, thereby giving off electromagnetic radiation, while other electrons cause further ionization of neutral atoms. Describe what happens to the pressure inside the vessel when the ionizing voltage is applied.

Question 30

During the day, the atmosphere is at a higher temperature than at night. What effects do you expect this will have on atmospheric density?

Question 31

The transmural pressure is the difference in pressure between two sides of a wall, or a separator. In the human respiratory system, the transmural pressure (trans means "across" and murus means "wall" in Latin) is a pressure difference between the lungs and the pleura. The pleura is a double-layered membrane surrounding the lungs and, with a small amount of fluid, allows frictionless movements of the lungs against the rib cage, preventing the hard ribs from puncturing the soft lung tissue. Gauge pressure is the pressure value relative to atmospheric pressure. P_alveoli represents the gauge pressure inside the lungs, and P_pleura represents the gauge pressure in the pleura. What happens with transmural pressure in the lungs an the environment where atmospheric pressure is much lower, such as on the 4205-m-high Mauna Kea volcano summit on the Big Island, Hawaii? Are there other considerations that need to be taken into account when thinking about respiration at high altitudes?

Question 32

On a sunny day, air rises over black surfaces, such as roads, which are warmed more effectively than areas of vegetation (cooled by transpiration). Explain.

Question 33

If two bodies at the same temperature are brought into contact, no heat flows between them.

Question 34

Weather balloons are only partially filled when released from the ground because pressure inside the balloon increases as the balloon rises.

Question 35

Gauge pressure is pressure value relative to 0 Pa.

Question 36

Deviations from ideal gas behaviour occur at high densities.

Question 37

Boyle's and Charles's experiments could be carried out for any gas, or mixture of gases.

Question 38

Helium gas liquefies at a very low temperature (4 K), whereas water vapour liquefies at a much higher temperature. Describe briefly what causes this difference.

Question 39

The ideal gas law assumes no interactions between molecules of the gas.

Question 40

In 1742, Anders Celsius was the first to propose a quantitative method for measuring temperatures. He defined the temperature scale, which we call in his honour the Celsius scale: in which T₀ is an arbitrary reference temperature, for example, the temperature at which the thermometer is filled with mercury. The term in the bracket is the fraction of the height change of the mercury column during a temperature change, and á_Hg is the coefficient of linear expansion of mercury. What is the unit of á_Hg?

Question 41

Two gases of different composition, but at the same temperature and pressure, are mixed together. What happens to the temperature of the mixture?

Question 42

A barometer may be constructed by immersing the open end of a glass tube that is partially filled with water and sealed at the other end, into a jar of water, leaving an air space above the water in the tube. It is proposed to measure changes in atmospheric pressure by changes in the height of the water in the column. Describe what effects might intrude to give erroneous readings of the actual pressure changes.

Question 43

Water boils when the partial pressure of water vapour equals the ambient atmospheric pressure. Explain why it is not possible to cook some foods above a certain altitude.

Question 44

Dalton's law assumes ideal gas behaviour. Discuss under what conditions deviations from ideal gas behaviour might occur, and justify your claims.