Topic 2.3: Gas Laws Questions

Estimate the average kinetic energy, in joules, of one molecule of air in a classroom at room temperature (20 °C).

Take k_B = 1.38 × 10⁻²³ J K⁻¹.

Outline two assumptions of the kinetic model of an ideal gas.

At constant pressure a fixed mass of gas has a volume of 2.4 m³ at a temperature of 300 K.

The gas is heated until its temperature reaches 450 K.

Calculate the new volume of the gas.

A fixed mass of gas has a volume of 8.0 L at a pressure of 250 kPa.

At the same temperature it is slowly compressed to a volume of 5.0 L.

Calculate the new pressure of the gas.

State what is meant by the absolute temperature of an ideal gas in terms of the motion of its particles.

A student verifies Boyle's law and finds that the product PV stays constant for a fixed mass of gas at constant temperature.

State the value being kept constant in this experiment, and state an appropriate SI unit for the constant PV.

State what is meant by one mole of a substance.

Two identical sealed containers each hold the same number of gas molecules at the same temperature.

Container 1 holds neon and container 2 holds the heavier gas krypton.

Compare the density and the pressure of the gas in the two containers.

Explain why the temperature must be expressed in kelvin, not in degrees Celsius, when using Charles' law or Gay-Lussac's law.

At constant pressure a fixed mass of gas is heated from 17 °C to 75 °C.

Deduce the percentage increase in the volume of the gas.

A fixed mass of gas occupies a volume of 1.6 × 10⁻² m³ at a pressure of 9.5 × 10⁴ Pa and a temperature of 22 °C.

Determine the number of molecules of gas present.

(k_B = 1.38 × 10⁻²³ J K⁻¹.)

Container A and container B hold the same ideal gas at the same pressure.

Container A has a volume of 2.0 × 10⁻³ m³ at a temperature of 320 K.

Container B has a volume of 3.0 × 10⁻³ m³ at a temperature of 300 K.

Determine the ratio of the amount of substance in B to that in A (n_B ÷ n_A).

A room has a volume of 75 m³ and contains air, treated as an ideal gas, at a pressure of 1.01 × 10⁵ Pa and a temperature of 20 °C.

Estimate the number of air molecules in the room.

(k_B = 1.38 × 10⁻²³ J K⁻¹.)

Using the kinetic model, describe how the particles of a gas exert a pressure on the walls of their container.

A sample of neon gas is heated from 17 °C to 217 °C at constant volume.

Take k_B = 1.38 × 10⁻²³ J K⁻¹.

Calculate the change in the average kinetic energy of one neon particle.

A sealed container holds a sample of helium, which behaves as a monatomic ideal gas.

The total internal energy U of the gas is plotted against its absolute temperature T.

The graph is a straight line through the origin.

The point (400 K, 2000 J) lies on the line.

Taking the molar gas constant as R = 8.31 J mol⁻¹ K⁻¹, the number of moles of helium in the sample is closest to

[Diagram: x-axis from 0 to 500 label T, y-axis from 0 to 2500 label U, polyline: (0,0)-(400,2000) "U vs T"]

At a constant temperature a student measures the pressure P of a fixed mass of gas at several volumes V and plots P against 1/V.

The points lie on a straight line through the origin that passes through (0.20 m⁻³, 5.0 Pa) and (0.50 m⁻³, 12.5 Pa).

Determine the constant in Boyle's law and state its SI unit, and explain why the graph is a straight line.

A sealed rigid container of gas is at a pressure of 200 kPa when its temperature is 290 K.

It is then heated to 348 K.

Show that the new pressure of the gas is about 240 kPa.

Four sealed flasks hold different ideal gases.

Each flask has the same volume, and the gases are at the same pressure and the same temperature.

The molar masses of the gases are: hydrogen 2 g mol⁻¹, helium 4 g mol⁻¹, nitrogen 28 g mol⁻¹ and oxygen 32 g mol⁻¹.

Identify which flask contains the smallest mass of gas, and justify your answer.

A 0.50 mol sample of oxygen gas, of molar mass 32 g mol⁻¹, is sealed in a rigid container of volume 0.040 m³ at a temperature of 350 K.

(a) Calculate the mass of the oxygen, in grams.

(b) Calculate the pressure of the gas. (R = 8.31 J K⁻¹ mol⁻¹.)