plumiFormulae, equations and amount of substance: OCR A‑Level Chemistry B questions
Every OCR A-Level Chemistry B exam question on DF Formulae, equations and amount of substance (specification points DF(a)), 2016–2025, with its mark scheme and examiner’s report.
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Q2(e)(i)
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Q2(e)(ii)
The whole paper ↗![June 2025 Paper 2, question 2(e)(ii): The students heat 0.20 g of (NH4)2SO4 with excess NaNO3. Calculate the volume of N2O (in cm3) that would be formed at 20 °C and 105 kPa. Volume = cm3 [4]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-jun25-02-eii-qp.webp?v=3)
![June 2025 AS Paper 1, question 13: Ethene, C2H4, reacts with HBr: C2H4 + HBr C2H5Br What mass of HBr (in g) will react exactly with 120 cm3 of ethene at RTP? A 0.4 B 0.8 C 4 D 8 Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun25-13-qp.webp?v=3)
Q22(d)
The whole paper ↗![June 2025 AS Paper 1, question 22(d): A scientist has 10.0 g of C2H5Cl in a pressurised container. What volume of gas (in dm3) would this give at 293 K and 101 000 Pa? Volume = dm3 [3]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun25-22-d-qp.webp?v=3)
![June 2024 Paper 1, question 23: 10 cm3 of an alkane react exactly with 35 cm3 oxygen in complete combustion at RTP. What is the alkane? A CH4 B C2H6 C C3H8 D C4H10 Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43301-jun24-23-qp.webp?v=3)
Q2(a)(i)
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Q2(a)(ii)
The whole paper ↗![June 2024 Paper 2, question 2(a)(ii): A student wishes to check this value by doing an experiment. Draw a labelled diagram of an apparatus the student could use. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43302-jun24-02-aii-qp.webp?v=3)
Q21(b)(i)
The whole paper ↗![June 2024 AS Paper 1, question 21(b)(i): Draw a labelled diagram of an apparatus they could use. [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun24-21-bi-qp.webp?v=3)
Q21(b)(ii)
The whole paper ↗![June 2024 AS Paper 1, question 21(b)(ii): Calculate the volume of gas (in cm3, measured at RTP) that they would expect to collect if they heated 0.10 g of sodium bicarbonate. volume = cm3 [2]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun24-21-bii-qp.webp?v=3)
Q2(e)
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Q3(b)
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![June 2023 Paper 1, question 26: What is the amount (in moles) of a gas that occupies 23 dm3 at 1.0 × 105 Pa and 293 K? A 0.94 mol B 1.4 mol C 14 mol D 94 mol Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h43301-jun23-26-qp.webp?v=3)
Q5(c)
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Q23(d)(i)
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Q4(c)
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Q31(d)
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![June 2022 AS Paper 1, question 16: The density of a gas is given by mass/volume. What is a correct expression for the density? A p/RT B Mr p/RT C RT/p D p/MrRT Your answer [1]](https://pub-e8a9dbab8e2a4d089f52b2a45e0d0b50.r2.dev/bank/h03301-jun22-16-qp.webp?v=3)
All 55 questions on Formulae, equations and amount of substance, as a list
- June 2025, Paper 2, Q2(e)(i) (4 marks): The students want to test Equation 2.1 by measuring the volume of dry N2O produced by heating (NH4)2SO4 with NaNO3. Draw a labelled diagram of an apparatus they
- June 2025, Paper 2, Q2(e)(ii) (4 marks): The students heat 0.20 g of (NH4)2SO4 with excess NaNO3. Calculate the volume of N2O (in cm3) that would be formed at 20 °C and 105 kPa. Volume = cm3 [4]
- June 2025, AS Paper 1, Q13 (1 mark): Ethene, C2H4, reacts with HBr: C2H4 + HBr C2H5Br What mass of HBr (in g) will react exactly with 120 cm3 of ethene at RTP? A 0.4 B 0.8 C 4 D 8 Your answer [1]
- June 2025, AS Paper 1, Q22(d) (3 marks): A scientist has 10.0 g of C2H5Cl in a pressurised container. What volume of gas (in dm3) would this give at 293 K and 101 000 Pa? Volume = dm3 [3]
- June 2024, Paper 1, Q23 (1 mark): 10 cm3 of an alkane react exactly with 35 cm3 oxygen in complete combustion at RTP. What is the alkane? A CH4 B C2H6 C C3H8 D C4H10 Your answer [1]
- June 2024, Paper 2, Q2(a)(i) (4 marks): People use magnesium carbonate to neutralise excess stomach acid. Magnesium carbonate reacts with hydrochloric acid in the stomach as shown in the equation. MgC
- June 2024, Paper 2, Q2(a)(ii) (2 marks): A student wishes to check this value by doing an experiment. Draw a labelled diagram of an apparatus the student could use. [2]
- June 2024, AS Paper 1, Q21(b)(i) (2 marks): Draw a labelled diagram of an apparatus they could use. [2]
- June 2024, AS Paper 1, Q21(b)(ii) (2 marks): Calculate the volume of gas (in cm3, measured at RTP) that they would expect to collect if they heated 0.10 g of sodium bicarbonate. volume = cm3 [2]
- June 2024, AS Paper 2, Q2(e) (5 marks): 0.327 g of a CFC produces 65.0 cm3 of vapour at a pressure of 101 000 Pa and a temperature of 293 K. Calculate the Mr of this CFC. Give your answer to an approp
- June 2024, AS Paper 2, Q3(b) (2 marks): C14H30 is another hydrocarbon found in diesel. 2.50 g of C14H30 is completely burned in oxygen. Calculate the volume of CO2 formed (in dm3) at RTP. volume of CO
- June 2023, Paper 1, Q18 (1 mark): 10 cm3 of pentane gas is burned in 100 cm3 of oxygen at constant pressure and 390 K. C5H12 + 8O2 5CO2 + 6H2O What volume of gas is present when all the pentane
- June 2023, Paper 1, Q26 (1 mark): What is the amount (in moles) of a gas that occupies 23 dm3 at 1.0 × 105 Pa and 293 K? A 0.94 mol B 1.4 mol C 14 mol D 94 mol Your answer [1]
- June 2023, Paper 2, Q5(c) (3 marks): 1.1 kg of a sample of impure calcium carbide produces 0.33 m3 of acetylene (at RTP) when reacted with water. Calculate the percentage purity of the sample. perc
- June 2023, AS Paper 1, Q9 (1 mark): A sample of a gas has a volume of 0.60 m3 under a pressure of 200 kPa and at 300 K. 9 How many moles of molecules are in this sample of gas? A 0.021 B 0.048 C 2
- June 2023, AS Paper 1, Q23(d)(i) (3 marks): Complete labelled diagrams of simple apparatus that could be used for Experiment 1 and Experiment 2. Experiment 1 Experiment 2 flow of cyanogen flow of cyanogen
- June 2023, AS Paper 2, Q4(c) (4 marks): Some of the ammonia produced in the Haber process is oxidised in the first step of a different process to make nitric acid, as shown in Equation 4.2. 4NH3(g) +
- June 2022, Paper 1, Q31(d) (4 marks): A solution contains 2.57 g dm–3 of sodium bromide. Calculate the minimum volume of chlorine gas (in cm3) required at 20 °C and 101 kPa to displace all the bromi
- June 2022, AS Paper 1, Q16 (1 mark): The density of a gas is given by mass/volume. What is a correct expression for the density? A p/RT B Mr p/RT C RT/p D p/MrRT Your answer [1]
- June 2022, AS Paper 1, Q19 (1 mark): Ammonia is made by the following reaction. N2(g) + 3H2(g) 2NH3(g) 40 cm3 of hydrogen is reacted with excess nitrogen. 10 cm3 of ammonia is found in the equilibr
- June 2022, AS Paper 2, Q2(b)(iii) (4 marks): Butane reacts with oxygen according to the following equation. C4H10 + 6½O2 4CO2 + 5H2O Calculate the volume of oxygen, in m3 (measured at RTP), required for th
- June 2022, AS Paper 2, Q4(b) (4 marks): 4.3 g of another liquid hydrocarbon present in petrol produce 554 cm3 of vapour at 60 °C and 250 kPa. Use these data to work out the Mr of the hydrocarbon. Mr =
- November 2021, AS Paper 1, Q10 (1 mark): What volume of CO2 (measured at RTP) is formed when 0.10 mol of Na2CO3 reacts with excess hydrochloric acid? 2.4 cm3 A 4.8 cm3 B 2400 cm3 C 4800 cm3 D Your answ
- November 2021, AS Paper 1, Q16 (1 mark): V m3 of a gas weighs m g at a pressure p Pa. What is the Mr of the gas? mRT A pV pV B mRT mpV C RT RTV D mp Your answer [1]
- November 2021, AS Paper 1, Q17 (1 mark): Methane reacts with oxygen as shown below. CH4 + 2O2 CO2 + 2H2O In several experiments, 10 cm3 of methane is completely reacted with 20 cm3 of oxygen. The tempe
- November 2021, AS Paper 2, Q3(f) (4 marks): The estimated annual global emissions of chloromethane, CH3Cl, are 8.0 × 102 tonnes. Calculate the volume of this chloromethane, in dm3, at a pressure of 1.00 ×
- November 2020, Paper 1, Q27 (1 mark): 100 cm3 0.75 mol dm−3 hydrochloric acid is added to 2.5 g calcium carbonate (M r = 100). 2HCl + CaCO3 CaCl 2 + CO2 + H2 What volume of CO2, in cm3, is produced
- November 2020, Paper 1, Q32(c)(iv) (4 marks): The density of Dead Sea water is 1.24 kg dm−3. The concentration of chloride ions is 208 g dm−3. Calculate the volume of chlorine (in dm3 at RTP) that is obtain
- November 2020, Paper 2, Q4(g)(iii) (2 marks): Calculate the maximum mass of maleic anhydride, C4H2O3, (in kg) that could be made from 15 m3 of butane (measured at RTP). Give your answer to an appropriate nu
- November 2020, AS Paper 1, Q23(b)(iv) (5 marks): 1.0 tonne of sodium is made in a cell. What volume (in m3) of chlorine will be produced at the same time, measured at 600 °C and 1.1 kPa? Give your answer to a
- June 2019, Paper 1, Q21 (1 mark): Sodium carbonate and hydrochloric acid react as follows. Na2CO3 + 2HCl 2NaCl + CO2 + H2O 0.010 mol of Na2CO3 is mixed with 0.015 mol of HCl. What volume of CO2
- June 2019, Paper 1, Q24 (1 mark): The reaction for the formation of sulfur trioxide is shown below. 2SO2(g) + O2(g) 2SO3(g) 60 cm3 of sulfur dioxide are mixed with 60 cm3 of oxygen and allowed t
- June 2019, Paper 1, Q33(d)(i) (2 marks): Calculate the amount in moles of ozone in 1.5 dm3 of ozone from the stratosphere. amount of ozone = mol [2]
- June 2019, Paper 1, Q33(d)(ii) (2 marks): Calculate the volume (in cm3) that this number of moles would occupy on the surface of the Earth where the pressure is 97 kPa and the temperature is 298 K. Give
- June 2019, Paper 2, Q2(b)(i) (4 marks): 12.0 g of SrCO3 are heated. Calculate the volume of CO2 (in cm3) that would be collected at 290 K and 155 kPa. Give your answer to an appropriate number of sign
- June 2019, Paper 2, Q5(b) (4 marks): The Article refers to a ‘back-of-the-envelope’ calculation. This shows that the number of acetylene molecules combusting is approximately 1.4 times greater than
- June 2019, AS Paper 1, Q4 (1 mark): What is the volume (in cm3) of 4.4 g of CO2 at RTP? 4 A 105.6 2.4 × 103 B 2.4 × 104 C D 105 600 Your answer [1]
- June 2019, AS Paper 2, Q1(f) (4 marks): Petrol contains hydrocarbons like octane, C8H18. Equation 1.1 shows the complete combustion of octane. C8H18(g) + 12½O2(g) 8CO2(g) + 9H2O(g) Equation 1.1 3.42 g
- June 2018, Paper 1, Q6 (1 mark): What is the volume of CO2 (in dm3) measured at RTP when 20 g CaCO3 completely decompose? 6 A 0.20 B 2.4 C 4.8 D 24 Your answer [1]
- June 2018, Paper 2, Q1(c) (3 marks): The students continue to heat the MgCO3 formed and realise that the compound is decomposing, giving off CO2 gas. The students want to obtain 200 cm3 CO2 at 290
- June 2018, Paper 2, Q3(f) (3 marks): Hydrogen peroxide concentration is often measured as ‘volume strength’. 1 cm3 of ‘1 volume’ hydrogen peroxide produces 1 cm3 of oxygen at RTP. Calculate the ‘vo
- June 2018, Paper 3, Q2(b) (3 marks): A 25.0 g sample of Hg2Cl2 is vaporised at 400 °C and a pressure of 101 kPa. A student assumes that the formula of the gaseous mercury chloride molecules is Hg2C
- June 2018, AS Paper 1, Q8 (1 mark): 1.0 g of solid carbon dioxide is vaporised. What volume of gas (in cm3) is produced at RTP? A 0.55 B 24 C 550 D 24 000 Your answer [1]
- June 2018, AS Paper 1, Q16 (1 mark): A sample of gas has a mass of m g and occupies a volume V m3 at a pressure p Pa and temperature T K. Which expression is correct for the Mr of the gas? A mRT /
- June 2018, AS Paper 2, Q1(e) (1 mark): Calculate the volume of gas (in cm3 at RTP) produced when 0.493 g of barium carbonate, BaCO3, is reacted with an excess of hydrochloric acid. (Mr of BaCO3 = 197
- June 2017, Paper 1, Q32(c) (3 marks): Calculate the volume of carbon dioxide (in dm3) at 298 K and 95.0 kPa that could be captured by reacting it with 1.00 kg of MgO. volume = dm3 [3]
- June 2017, AS Paper 1, Q7 (1 mark): A sample of gas, volume V, has its temperature raised from 0 °C to 20 °C. The pressure remains constant. What is the new volume? A 0.005 V B 0.93 V C 1.07 V D 2
- June 2017, AS Paper 1, Q14 (1 mark): CuCO3 CuO + CO2 0.618 g of copper carbonate (Mr = 123.5) is heated. What is the volume of CO2 produced at room temperature and pressure? 120 cm3 A 1.2 dm3 B 240
- June 2017, AS Paper 1, Q23(b)(ii) (3 marks): A sample of a fuel produces 46 g of carbon dioxide when burned. Calculate the volume (in cm3) that this would occupy at 273 K and 150 kPa. Give your answer to a
- June 2017, AS Paper 2, Q3(a)(iii) (1 mark): Calculate the volume (in m3) that this chlorine would occupy at RTP. volume = m3 [1]
- June 2017, AS Paper 2, Q4(a)(ii) (2 marks): The student reacts 1.26 g of calcium with excess water. Calculate the volume of hydrogen (in cm3) produced at RTP. Ca(s) + 2H2O(l) Ca(OH)2(aq) + H2(g) Give your
- June 2016, AS Paper 1, Q7 (1 mark): What is the effect on the volume when the pressure of an ideal gas is doubled at the same time as the temperature (in Kelvin) is doubled? A halved B remains the
- June 2016, AS Paper 1, Q23(b)(iv) (3 marks): 37 kg of NaOH is produced (in solution) in a membrane cell. Calculate the volume of Cl2 (in dm3 at RTP) that will be produced at the same time. Give your answer
- June 2016, AS Paper 1, Q24(c) (4 marks): The model uses a temperature of 300 K and a pressure of 1000 Pa. Calculate the total number of molecules in 1.0 cm3 of gas under these conditions. total number
- June 2016, AS Paper 2, Q4(d)(i) (2 marks): Calculate the minimum volume of oxygen (measured in cm3 at RTP) required. minimum volume of oxygen at RTP = cm3 [2]
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