States of matter — AS & A Level Chemistry (9701) questions by topic
Expect gas-law calculations throughout this topic: concentration of dissolved oxygen from volume and pressure data, final gas volumes after combustion, densities of gases assuming ideal behaviour, and identifying a limiting reagent before applying pV = nRT.
Calculate, identify, state and deduce are the command words across 21 questions from 2023 to 2025 papers, each a 1-mark item that rewards speed and accuracy over multi-step reasoning. Instant marking after each short calculation catches a wrong assumption about ideal gas volume or a missed limiting-reagent check before it becomes a habit across the paper.
What examiners look for
- A common mistake was choosing B by failing to identify HCl as the limiting reagent in the magnesium reaction.
- Reports note uncertainty over whether ideal gas molecules are assumed to have no mass or no volume; the syllabus assumption is no volume.
- Strong scripts worked through the full method: 0.070 mol Mg, 0.11 mol HCl, HCl as limiting reagent, 0.055 mol H2, then pV = nRT to reach 1.3 dm3.
- Examiners note candidates who correctly stated that ideal gases have no intermolecular forces and that the gas molecules themselves have no volume scored well.
May–June 2025, Paper 11
The diagram shows two containers of methane connected by a closed tap. Each container has a volume of 1.00 m^3. Container 1: 16 g methane at 100 kPa Container 2: 96 g methane at…
Answer this question and get it marked →May–June 2025, Paper 12
A sample of an ideal gas occupies 240 cm^3 at 37 °C and 100 kPa. How many moles of gas are present in the sample? A 9.32 × 10^-6 B 9.32 × 10^-3 C 0.0781 D 78.1
Answer this question and get it marked →May–June 2025, Paper 13
When 0.15 g of an organic compound is vaporised, it occupies a volume of 65.0 cm^3 at 405 K and 1.00 × 10^5 Pa. Using the expression pV = nRT, which expression should be used to…
Answer this question and get it marked →May–June 2025, Paper 14
Two glass vessels, M and N, are connected by a closed valve. M contains helium at 20 °C at a pressure of 1 × 10^5 Pa. N has been evacuated, and has three times the volume of M.…
Answer this question and get it marked →May–June 2024, Paper 11
What is the density of a sample of fluorine gas at 32 degC and 100 000 Pa? Assume fluorine behaves as an ideal gas under these conditions. A 1.4 g dm^-3 B 1.5 g dm^-3 C 1.6 g…
Answer this question and get it marked →May–June 2024, Paper 12
In this question it should be assumed that nitrogen behaves as an ideal gas under the conditions stated. Which volume is occupied by 1.00 g of nitrogen at 50.0 degC and at a…
Answer this question and get it marked →May–June 2024, Paper 13
The diagram shows the apparatus used to find the relative molecular mass of a volatile liquid: a gas syringe heated in an enclosure, with a thermometer and a heater, into which…
Answer this question and get it marked →October–November 2024, Paper 12
In this question you may assume that nitrogen behaves as an ideal gas. One atmosphere pressure = 101 kPa. Which volume does 1.0 g of nitrogen occupy at 50 °C and a pressure of 2.0…
Answer this question and get it marked →February–March 2023, Paper 12
Under which conditions will nitrogen behave most like an ideal gas? temperature pressure --- --- --- A low high B high low C low low D high high
Answer this question and get it marked →Hydrated cobalt(II) sulfate loses water when heated to give anhydrous cobalt(II) sulfate. All the water of crystallisation is lost to the atmosphere as steam. When 3.10 g of…
Answer this question and get it marked →May–June 2023, Paper 11
In the sodium chloride lattice the number of chloride ions that surround each sodium ion is called the coordination number of the sodium ions. What are the coordination numbers of…
Answer this question and get it marked →In this question you should assume that the gas formed behaves as an ideal gas. A 1.7 g sample of Mg reacts with 50.0 cm³ of 2.2 mol dm⁻³ HCl at 303 K and 110 400 Pa. Which volume…
Answer this question and get it marked →May–June 2023, Paper 12
The volume of a vessel is 1.20 x 10^-3 m3. It contains pure argon at a pressure of 1.00 x 10^5 Pa, and at a temperature of 25.0 degC. Under these conditions it can be assumed that…
Answer this question and get it marked →May–June 2023, Paper 13
Which assumptions are made about ideal gases? 1 Ideal gases contain molecules with no mass. 2 Ideal gases contain molecules with no volume. 3 Ideal gases have no intermolecular…
Answer this question and get it marked →A 200 cm3 sample of water has an amount of oxygen gas dissolved in it. This amount of oxygen gas has a volume of 6.00 cm3 when measured at 1.00 x 10^5 Pa and 35 degC. What is the…
Answer this question and get it marked →October–November 2023, Paper 11
A sample of 35.6 g of hydrated sodium carbonate contains 25.84% sodium ions by mass. When this sample is heated, anhydrous sodium carbonate and water are formed. Which mass of…
Answer this question and get it marked →When an evacuated tube of volume 400 cm3 is filled with gas at 300 K and 101 kPa, the mass of the tube increases by 0.65 g. Assume the gas behaves as an ideal gas. What is the…
Answer this question and get it marked →October–November 2023, Paper 12
In an experiment, 0.100 mol of propan-1-ol is burnt completely in 12.0 dm3 of oxygen, measured at room conditions. What is the final volume of gas, measured at room conditions? A:…
Answer this question and get it marked →At a temperature of 2500 K and a pressure of 1.00 x 10^-4 Pa, a sample of 0.321 g of sulfur vapour has a volume of 2.08 x 10^6 m3. What is the molecular formula of sulfur under…
Answer this question and get it marked →A mixture of the three gases oxygen, nitrogen and argon is at a total pressure of 500 kPa; there is a total of 1.2 moles of gas in the mixture. If the oxygen gas alone occupied…
Answer this question and get it marked →October–November 2023, Paper 13
When an evacuated tube of volume 400 cm3 is filled with gas at 300 K and 101 kPa, the mass of the tube increases by 0.65 g. Assume the gas behaves as an ideal gas. What is the…
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