03 The Gaseous State, Set B To print: Ctrl + P, paper A4, margins Default.
Learners' AlleyDesigned by Khow Willard
03
The Gaseous State
Set BExam practice
Name
Time 1 hour
Total 36 marks
Data: R = 8.31 J mol−1 K−1, 1 atm = 101 325 Pa, L = 6.02 × 1023 mol−1, Ar: H 1.0,C 12.0,N 14.0,O 16.0,Ar 39.9.
A
Multiple choice
3 marks
1
A 5.0 dm3 sample of oxygen at a pressure of 200 kPa and a 2.0 dm3 sample of nitrogen at a pressure of 500 kPa are put into a 2.5 dm3 vessel at constant temperature.
What is the total pressure in the vessel?
A500 kPa
B700 kPa
C725 kPa
D800 kPa
Answer [1]
Source: N01/3/6, via EJC 2022 JC1 Gaseous State Tutorial, B2
2
At 400 K, the following species behave as ideal gases: H2, CH4, NO2, Ar. 5.00 g of each gas is put separately into a gas syringe kept at 400 K. The volume of each gas is adjusted to be the same, and the pressure is measured.
Which gas will have the lowest pressure?
AH2
BCH4
CNO2
DAr
Answer [1]
Source: 2023 CJC J2 Prelim P1 Q7
3
CommonWhich gas would behave most like an ideal gas under room conditions?
Aammonia
Bhelium
Ckrypton
Dnitrogen
Answer [1]
Source: 2023 YIJC J2 Prelim P1 Q2
B
Structured questions
33 marks
4
(a)
CommonState two conditions under which real gases behave most ideally.
[1]
(b)
Calculate the volume, in dm3, of 5.2 mol of an ideal gas at 101 300 Pa and 15 °C.
[1]
(c)
5.2 mol of ammonia gas under the same conditions as in (b) occupies 117 dm3. Explain, in terms of the properties of ammonia molecules, why this volume is lower than that of an ideal gas.
[1]
Source: 2023 RI J2 Prelim P3 Q2(a)
5
(a)
CommonState three ways in which an ideal gas differs from a real gas.
[3]
(b)
(i) Draw a labelled diagram to show the significant force of attraction between two molecules of hydrogen fluoride. Name the attraction in your diagram.
[2]
Common(ii) The graph shows pV/RT against p for 1 mol of an ideal gas and 1 mol of fluorine at 300 K. On the same axes, sketch pV/RT against p for 1 mol of hydrogen fluoride at 300 K. Explain your answer.
[2]
Source: 2023 VJC J2 Prelim P2 Q1
6
NH3 is used in space missions and in many chemical reactions.
(a)
On the axes below, sketch a graph of pV/T against pressure, p, for 1 mol of an ideal gas.
[1]
(b)
CommonOn the same axes, sketch and label the graph for 1 mol of NH3. Explain the non-ideal behaviour of NH3 at moderately high pressure.
[2]
(c)
NH3 is held in a 5.00 dm3 flask at 27 °C and 4.00 atm. The gas is compressed at constant temperature to half its volume, then heated to 227 °C at constant volume. Assuming ideal behaviour, calculate the final pressure, in atm.
[2]
Source: 2025 RI J2 Prelim P3 Q1(a)(ii) to (iv)
7
Indirect calorimetry estimates the energy a person uses from the difference in oxygen content between inhaled and exhaled air. In aerobic respiration at 37 °C, glucose is oxidised in reaction 1.
Air contains about 21% oxygen by volume, and exhaled air contains 14%. At rest, an adult breathes about 500 cm3 of air per breath, 12 times a minute, at 37 °C and 1 atm. Assuming oxygen is an ideal gas, calculate the volume of oxygen used per minute, and hence the amount of oxygen used per minute.
[3]
(b)
Assuming all the oxygen used is consumed in reaction 1, calculate the energy released per minute.
[1]
Source: 2025 EJC J2 Prelim P3 Q1(a)(ii) and (iii)
8
CommonThe graph shows pV/RT against p for one mole of iodobutane gas at 200 °C.
compound
boiling point / °C
bromobutane
101
iodobutane
131
On the graph, show how one mole of bromobutane behaves at the same temperature.
[1]
Source: 2025 DHS J2 Prelim P2 Q2(d)(ii)
9
CommonHydrazine, N2H4, is used as a rocket fuel. N2H4 does not behave as an ideal gas. State and explain two reasons for its deviation from ideal behaviour.
[2]
Source: 2025 ACJC J2 Prelim P3 Q1(d)(iii)
10
Noble gases such as neon are used in discharge tubes ("neon" lights).
(a)
Common(i) Give two reasons why the noble gases behave less ideally down the group from He to Xe.
[2]
(ii) A mixture of krypton and xenon is obtained from air. At 300 K and 8.00 × 104 Pa, 1.00 dm3 of the mixture has a mass of 2.79 g. Calculate the average Mr of the mixture.
[2]
(b)
A sample of naturally occurring krypton has the isotopic composition below. Calculate the Ar of krypton.
nucleon number
80
82
83
84
86
relative abundance / %
2.4
11.7
11.6
56.9
17.4
[1]
(c)
An evacuated 1.00 dm3 glass bulb gains 3.40 g when it is filled with another sample of krypton at 293 K and 1.00 × 105 Pa. Calculate the Ar of this sample. Is its isotopic composition likely to be the same as in (b)? Explain your answer.
[3]
Source: N95/1/3, modified, via EJC 2022 JC1 Gaseous State Tutorial, B3
11
ChallengeXenon and fluorine are mixed in a 1 : 1 ratio by volume and sealed in a vessel at constant temperature. Crystals form on the walls, and the pressure falls to 70% of its starting value. The gases left contain 4 parts xenon to 3 parts fluorine. Deduce the equation for the reaction.