Deck 8: Gases

Question 1

What is the pressure exerted by a column of mercury 43 cm high, given that the density of mercury is 13.6 g cm^-3? Give your answer in base SI units.

A) 5736.89 g cm^-2 m s^-2.
B) 57.37 g cm^-3 m² s^-2.
C) 57368.88 kg m^-1 s^-2.
D) 5736888 g cm^-1 s^-2.

Answer 1

C

Question 2

Which of the following units are commonly used for pressure? Select all that apply.

A) Pa.
B) bar.
C) kg m s^-2.
D) N m^-2.

Answer 2

A, B, D

Question 3

At constant temperature, the volume of a fixed amount of gas ______________ with increasing pressure.

Answer 3

decreases

Question 4

As the temperature of a fixed amount of gas, increases at constant pressure, its volume decreases.

Question 5

Avogadro's law states that at constant pressure and temperature, a different number of molecules will be present in equal volumes of oxygen and carbon dioxide.

Question 6

Calculate the pressure (in Pa) required to compress 0.25 dm³ of a gas at 1 atm to a volume of 0.10 dm³ at the same temperature?

A) 2.5
B) 2.5 × 10⁵.
C) 1.0
D) 1.01 × 10⁵.

Question 7

What would be the volume (in dm³ ) of N₂ at 293 K and 720 Torr if it occupied 12.5 dm³ at 329 K and 0.947 atm?

A) 14.04
B) 12.5
C) 11.13
D) 11.84

Question 8

A balloon is filled at 1 atm with gas that occupies 2.3 dm³ in a laboratory at 19 °C. The balloon is then taken from this laboratory to a tropical greenhouse at 1 atm where the temperature is 38 °C. What is the resulting volume (dm³) of the balloon?

A) 4.6
B) 2.3
C) 2.16
D) 2.45

Question 9

Combining Boyle's law, Charles's law and Avogadro's law gives the _____ gas equation.

Question 10

The gas constant R can be expressed in different units. Select all that apply.

A) N m K^-1 mol^-1.
B) dm³ atm mol^-1 K^-1.
C) J K^-1 mol^-1.
D) dm³ Torr K^-1 mol^-1.

Question 11

A 28.0 dm³ gas cylinder at 5.2 atm and 23 °C contains only carbon monoxide gas. What is the mass (in kg) of carbon monoxide in the tank?

A) 168.
B) 0.168
C) 0.021
D) 1.656 × 10^-6.

Question 12

A balloon is filled with 39.3 g of helium at 29 °C and 2.75 atm. What is the volume of the balloon in dm³?

A) 88.52
B) 8.852 × 10^-2.
C) 8.97 × 10⁶.
D) 8.50

Question 13

A 5.2 dm³ gas cylinder containing 822 g of neon is heated until the pressure reaches 232 atm. What is the temperature in °C of the gas?

A) - 273.15
B) 87.80
C) 360.95
D) -255.26

Question 14

Equal volumes of carbon dioxide and a second gas weigh 32.00 g and 14.67 g respectively under the same experimental conditions. Which of the following is the unknown gas?

A) He
B) O₂
C) Ne
D) Ar

Question 15

A small bottle of nitrogen gas, volume 6.5 dm³ is stored at 22 °C and a pressure of 63 bar. Calculate the pressure (in bar) inside the bottle when the temperature increases to 28 °C; assume the gas behaves as an ideal gas.

A) 49.5
B) Not enough information to calculate the new pressure.
C) 7.08 × 10^-4
D) 64.28

Question 16

A sealed reaction vessel volume is 0.5 dm³ contains argon gas at 1 atm and 21 °C. Assuming that argon behaves ideally under these conditions calculate the mass of Ar in the reaction vessel.

A) 0.11 g.
B) 0.0005 g.
C) 0.83 g.
D) 8.17 × 10^-6 g.

Question 17

A reaction vessel is fitted with a syringe. It contains gas at 1 atm and 18 °C. Calculate the pressure if the syringe is moved so that it is a quarter of its original volume. Assume temperature to be constant.

A) 1 atm.
B) 0.25 atm.
C) 101 325 Pa.
D) 4 atm

Question 18

The IUPAC definition of standard ambient temperature and pressure, SATP, is 298.15 K and 1 atm.

Question 19

Calculate the molar volume of one mole of an ideal gas under conditions of standard ambient pressure and temperature.

A) 0.0248 m³ .
B) 0.0245 m³.
C) 0.0227 m³ .
D) 0.0224 m³.

Question 20

A gas-mixing cylinder is filled with a mixture of He, Ne and Ar, in a 1:1:2 ratio. The total pressure in the gas-mixing cylinder is 3.29 × 10⁵ Pa. Calculate the partial pressure of helium in the mixture.

A) 164500 Pa.
B) 75000 Pa.
C) 82250 Pa.
D) 25000 Pa.

Question 21

The kinetic molecular theory describes gas behaviour in terms of the movement of molecules. In developing the model, which assumptions were made? Select all that apply.

A) The motion of the gas molecules is constant and random.
B) Gas molecules have negligible size compared to the vessel in which the gas is contained.
C) Any collisions between the molecules and the walls of the container will increase the energy of the molecules.
D) The molecules do not interact with each other.

Question 22

Calculate the root mean square speed of argon gas at 15 °C. Give your answer in m s^-1.

A) 96.
B) 424.
C) 13.
D) 3.

Question 23

Calculate the root mean square speed of ammonia gas at 17 °C. Give your answer in m s^-1.

A) 158.
B) 21.
C) 5.
D) 652.

Question 24

A 0.25 dm³ sealed container is filled with 3 mol of He, with a root mean square molecular speed, c = 1250 m s^-1. Find the pressure exerted by the gas (in k Pa).

A) 25.02
B) 0.25 × 10⁵.
C) 1.51 × 10²⁸.
D) 1.51 × 10²⁵.

Question 25

The molecular speed distribution of neon will change with temperature. Select all that apply.

A) At higher temperatures, the average speed will be greater than at lower temperatures.
B) At higher temperatures, the spread of speeds will be greater than at lower temperatures.
C) At lower temperatures, the distribution of speeds will be greater than at higher temperatures.
D) At lower temperatures, the average speed will be greater than at higher temperatures.

Question 26

1 mol of Xe gas at 345 K will have a greater distribution of molecular speeds and higher average speed than 1 mol of He at the same temperature.

Question 27

Rank the following gases, in order of rate of effusion (from highest to lowest rate) through a porous film under the same experimental conditions.

A) O₃
B) O₂
C) CO₂
D) CO

Question 28

35 mol of nitrogen gas passes through a membrane in 30 minutes. How long will it take for the same amount of carbon dioxide to pass through the same membrane? Give your answer to the nearest whole minute.

A) 38 min.
B) 24 min.
C) 47 min.
D) 19 min.

Question 29

Calculate the relative rates of effusion of helium, neon, argon, and xenon through a gas cylinder regulator.

A) 1:2.25:3.16:5.73
B) 1:0.45:0.32:0.17
C) 1:0.20:0.10:0.03
D) 1:0.45:0.71:0.55

Question 30

Match the characteristic property of molecules in a gas with its description.
-collision cross section, σ

A) target area of a molecule
B) number of collisions per second
C) average distance travelled by a molecule between collisions
D) product of collision frequency and mean free path

Question 31

Match the characteristic property of molecules in a gas with its description.
-collision frequency, Z

A) target area of a molecule
B) number of collisions per second
C) average distance travelled by a molecule between collisions
D) product of collision frequency and mean free path

Question 32

Match the characteristic property of molecules in a gas with its description.
-mean free path, λ

A) target area of a molecule
B) number of collisions per second
C) average distance travelled by a molecule between collisions
D) product of collision frequency and mean free path

Question 33

Match the characteristic property of molecules in a gas with its description.
-mean speed,

A) target area of a molecule
B) number of collisions per second
C) average distance travelled by a molecule between collisions
D) product of collision frequency and mean free path

Question 34

How many collisions will O₂ undergo in 1 s at SATP? (For O₂ σ = 0.40 nm², 444 m s^-1 at 298 K.)

A) 6.1 × 10⁹.
B) 6.1 × 10²⁷.
C) 6.1 × 10¹⁸.
D) 6.1 × 10⁴.

Question 35

Calculate the pressure (in Pa) at which O₂ has a mean free path of 0.5 cm. (For O₂, σ = 0.40 nm², 444 m s^-1 at 298 K).

A) 1.46 × 10^-17.
B) 1.46 × 10^-8.
C) 1.46
D) 1.46 × 10^-2.

Question 36

The ideal gas equation is an example of a limiting law. It describes well the behaviour of gases as gas pressure tends to ____.

Question 37

The van der Waals equation for gases is The van der Waals constants a and b attempt to correct for the behaviour of real gases relative to ideal behaviour. The constants correct for which of the following: select all that apply.

A) The reduced pressure of real gases with respect to ideal gases.
B) The increased pressure of real gases with respect to ideal gases.
C) The reduced volume available for real gas molecules to move in.
D) The increased volume available for real gas molecules to move in.

Question 38

A reaction vessel (volume 0.5 dm³) is filled with 3 mol of hydrogen gas at 25 °C. Calculate the pressure, (in Pa) it exerts using the van der Waals equation. For hydrogen, the van der Waals constants are a = 0.025 Pa m⁶ mol^-2 and b = 2.7 × 10^-5 m³ mol^-1.

A) 1.68 × 10⁷.
B) 1.49 × 10⁷.
C) 5.88 × 10⁵.
D) - 9 × 10⁵.