3.2 Modelling a Gas

Question 2a

Marks: 1

(a)

State what is meant by an ideal gas.

[1]

Key Concepts

Question 2b

Marks: 3

(b)

State the conditions for a real gas to approximate to an ideal gas.

[3]

Key Concepts

Real & Ideal Gases

Question 2c

Marks: 2

(c)

Describe how the ideal gas constant, R, is defined.

[2]

Key Concepts

Question 2d

Marks: 2

The graphs shows how pressure, p, varies with absolute temperature, T, for a fixed mass of an ideal gas.

3-2-q2d-sl-sq-easy-phy

(d)

Outline the changes, or otherwise, to the volume and density of the ideal gas as the absolute temperature increases.

[2]

Key Concepts

Question 3a

Marks: 3

(a)

State three assumptions of the kinetic model of an ideal gas.

[3]

Key Concepts

Question 3b

Marks: 3

A tank of volume 21 m³ contains 7.0 moles of an ideal monatomic gas. The temperature of the gas is 28 °C.

(b)

Calculate the average kinetic energy of the particles in the gas.

[3]

Key Concepts

Question 3c

Marks: 3

The following paragraph explains, with reference to the kinetic model of an ideal gas, how an increase in temperature of the gas leads to an increase in pressure.

A ________ temperature implies ________ average speed and therefore higher ________. This increases the ________ transferred to the walls from ________ frequent collisions. This increased ________ per collision leads to an increased ________.

(c)

Complete the sentences using keywords from the box below.

[3]

Key Concepts

Question 3d

Marks: 3

(d)

Calculate the pressure of the gas described in part (b).

[3]

Key Concepts

Question 4a

Marks: 2

(a)

Sketch on both axes the change in pressure and volume for an ideal gas at constant temperature.

[2]

Key Concepts

Question 4b

Marks: 2

(b)

Sketch the graphs in part (a) at a higher temperature.

[2]

Key Concepts

Question 4c

Marks: 1

For an ideal gas at constant volume, the pressure, p, and temperature, T, are directly proportional:

$p \propto T$

(c)

State the equation for an initial pressure p₁ at temperature T₁ and final pressure p₂ and temperature T₂.

[1]

Key Concepts

Question 4d

Marks: 3

The final pressure of an ideal gas is 500 Pa and its temperature rises from 410 K to 495 K.

(d)

Calculate the initial pressure of the gas.

[3]

Key Concepts

Question 5a

Marks: 1

(a)

Define pressure.

[1]

Key Concepts

Question 5b

Marks: 4

When there are a large number of particles in a container, their collisions with the walls of the container give rise to gas pressure.

An ideal gas with a pressure of 166 kPa collides with the walls of its container with a force of 740 N.

(b)

Calculate the area that each particle collides on.

[4]

Key Concepts

Question 5c

Marks: 2

An ideal gas is one that obeys the relationship

$p V \propto T$

(c)

If the volume an ideal gas increases, explain how this affects the:

(i)

Pressure, if the temperature remains constant.

[1]

(ii) Temperature, if the pressure remains constant.

[1]

Key Concepts

Question 5d

Marks: 1

The ideal gas equation can be rearranged to give

$\frac{p V}{T} =$ constant

This relationship only holds true under a certain condition.

(d)

State the condition required for the equation to apply to an ideal gas.

[1]

Key Concepts