plumiThe mole and molar mass: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 2.1.3.1 The mole and molar mass, 2016–2025, with mark schemes and examiner’s reports where available.
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Q2(a)(ii)
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All 34 questions on The mole and molar mass, as a list
- June 2025, Paper 3, Q2(a)(ii) (3 marks): What is the number of H atoms in 8.45 g of 2,3‑dimethylhexan‑1‑ol? Give your answer to 3 significant figures and in standard form. Number of H atoms = [3]
- June 2025, AS Paper 1, Q3 (1 mark): What is the number of hydrogen atoms in 6.8 g NH3? 2.408 × 1023 A 3.612 × 1023 B 7.224 × 1023 C 1.806 × 1024 D Your answer [1]
- June 2025, AS Paper 1, Q5 (1 mark): Phosphorus is burnt in oxygen to produce a mixture of oxides. Which oxide has the closest to 50% by mass of phosphorus? A PO2 B P2O3 C P2O5 D P4O9 Your answer [
- June 2024, Paper 3, Q2(c)(iii) (2 marks): A research chemist synthesises two related compounds, compound C and compound D, from compound B. • In compound C, the N atoms in compound B had been replaced b
- June 2024, Paper 3, Q4(c)(ii) (2 marks): Calculate the percentage by mass of P in P3N3Cl 6. Give your answer to 2 decimal places. percentage by mass of P = % [2]
- June 2023, Paper 1, Q1 (1 mark): Which sample contains the greatest number of molecules? A 35.0 g of C2H2 B 45.0 g of C2H6 C 60.0 g of C4H10 D 100.0 g of C6H6 Your answer [1]
- June 2023, Paper 1, Q3 (1 mark): How many hydrogen atoms are in 2.50 g of pharmacolite, CaHAsO4•2H2O (Mr = 216.0)? 6.97 × 1021 A 2.09 × 1022 B 2.79 × 1022 C 3.48 × 1022 D Your answer [1]
- June 2023, Paper 2, Q20(b)(ii) (3 marks): For the treatment of TB, the maximum daily dosage of PAS that should be prescribed is 300 mg per kg of body mass. A child weighs 20.0 kg. Calculate the number o
- June 2023, Paper 3, Q1(h) (1 mark): The element with an average atomic mass of 1.244 × 10–22 g. [1]
- June 2023, Paper 3, Q4(b)(i) (2 marks): What masses are needed of ammonium sulfate and CuSO4 • 5H2O? mass of ammonium sulfate g mass of CuSO4 • 5H2O g [2]
- June 2023, AS Paper 1, Q7 (1 mark): How many oxygen atoms are in 120.2 g of SiO2? 3.01 × 1023 A 1.20 × 1024 B 2.41 × 1024 C 3.61 × 1024 D Your answer [1]
- June 2022, Paper 1, Q5 (1 mark): The mass of 4 molecules of a substance is 2.125 × 10–22 g. 5 What is the possible formula of the substance? A CH4 B O2 C SO2 D I2 Your answer [1]
- June 2022, Paper 1, Q18(b) (1 mark): Estimate the energy required to form one Li+(g) ion from one Li(g) atom. Give your answer in kJ, in standard form, and to two significant figures. energy = kJ [
- June 2022, Paper 2, Q8 (1 mark): The structure of the painkiller, paracetamol, is shown below. OH O N H paracetamol A tablet contains 3.31 × 10–3 mol of paracetamol. What is the mass of paracet
- June 2022, Paper 3, Q5(b)(ii) (3 marks): Calculate the energy released, in kJ, by the complete combustion of 8.00 kg of this fuel. ∆cH(C8H18) = –5470 kJ mol–1; ∆cH(C2H5OH) = –1367 kJ mol–1. energy rele
- June 2022, AS Paper 1, Q9 (1 mark): What is the number of ions in 4.00 mol of magnesium chloride, MgCl2? 1.81 × 1024 A 2.41 × 1024 B 4.82 × 1024 C 7.22 × 1024 D Your answer [1]
- November 2021, Paper 1, Q4 (1 mark): Which sample contains the greatest number of molecules? A 140.0 g C2H2 B 180.0 g C2H6 C 240.0 g C4H10 D 400.0 g C6H6 Your answer [1]
- November 2021, Paper 2, Q3 (1 mark): Which sample contains the greatest number of carbon atoms? A 20.0 g C6H5OH B 30.0 g C2H5COOH C 40.0 g CH3CHO D 50.0 g CH3OH Your answer [1]
- November 2021, Paper 2, Q18(c)(ii) (3 marks): One ibuprofen tablet contains 400 mg of ibuprofen. Calculate the number of ibuprofen molecules in one ibuprofen tablet. Give your answer to 3 significant figure
- November 2021, AS Paper 1, Q21(d)(ii) (2 marks): What is the number of fluorine atoms in 7.896 g of halothane, C2HBrCl F3? number of fluorine atoms = [2]
- November 2020, Paper 1, Q2 (1 mark): Which statement gives the numerical value of the Avogadro constant? A The number of moles in 12 g of carbon-12. B The number of electrons lost by 20.05 g of cal
- November 2020, Paper 1, Q16(b)(ii) (3 marks): Calculate the total number of ions in 1.74 g of magnesium bromide, MgBr2. Give your answer to 3 significant figures. number of ions = [3]
- November 2020, Paper 2, Q21(b)(iii) (3 marks): Some people are concerned that aspartame, C14H18N2O5, may have adverse health effects. Research shows that the safe maximum daily intake of aspartame is 1.7 × 1
- November 2020, AS Paper 1, Q10 (1 mark): Which sample contains the greatest number of molecules? A 1 g of methanol, CH3OH B 2 g of nitrogen dioxide, NO2 C 3 g of phosphorus, P4 D 4 g of iodine, I2 Your
- June 2019, Paper 1, Q3 (1 mark): One molecule of a gas has a mass of 2.658 × 10−23 g. 3 What is a possible formula of the gas? A CH4 B O2 C SO2 D SO3 Your answer [1]
- June 2019, Paper 3, Q1(f) (2 marks): What is the number of oxygen atoms in 4.26 g of P2O5? number of oxygen atoms = [2]
- June 2018, Paper 1, Q3 (1 mark): What is the number of hydrogen atoms in 0.125 mol of C2H5OH? 7.525 × 1022 A B 4.515 × 1023 3.7625 × 1023 C D 3.612 × 1024 Your answer [1]
- June 2018, Paper 3, Q1(a)(vi) (1 mark): The element X, which forms a compound with hydrogen, XH3, with a molar mass of 34.0 g mol–1. [1]
- June 2018, AS Paper 1, Q2 (1 mark): What is the number of oxygen atoms in 88.0 g of CO2? 3.01 × 1023 A 1.20 × 1024 B 2.41 × 1024 C 4.82 × 1024 D Your answer [1]
- June 2017, Paper 1, Q6 (1 mark): How many electrons are removed from 2.02 × 10–2 g of Ne(g) atoms to form Ne+(g) ions? 6 3.36 × 10–26 A 1.66 × 10–27 B 6.02 × 1020 C 1.22 × 1022 D Your answer [1
- June 2017, Paper 2, Q12 (1 mark): 0.1 mol of HOOCCH2COOH are reacted with 0.1 mol of aqueous NaOH. How many molecules of water are formed? 6.02 × 1022 A 3.01 × 1022 B 6.02 × 1023 C 3.01 × 1023 D
- June 2017, AS Paper 1, Q22(c)(ii) (1 mark): Estimate the energy required to form one Na+(g) ion from one Na(g) atom. Give your answer in kJ, in standard form, and to two significant figures. energy = kJ [
- June 2017, AS Paper 2, Q1(a)(iii) (2 marks): Calculate the number of barium ions in 1.50 g of barium oxide. Give your answer in standard form and to three significant figures. number of barium ions = [2]
- June 2016, AS Paper 1, Q21(b)(ii) (2 marks): One coin has a mass of 5.00 g and contains 84.0% of copper, by mass. Calculate the number of copper atoms in one coin. Give your answer in standard form and to
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