plumiStandard enthalpy change definitions: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 3.2.1.2 Standard enthalpy change definitions, 2016–2025, with mark schemes and examiner’s reports where available.
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Q17(a)(i)
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All 19 questions on Standard enthalpy change definitions, as a list
- June 2025, Paper 1, Q17(a)(i) (1 mark): [1]
- June 2025, AS Paper 2, Q4(b)(ii) (2 marks): Use the information in Table 4.1 to calculate the mass of carbon dioxide formed when 1.00 kJ of energy is released during the complete combustion of pentane. Ma
- June 2025, AS Paper 2, Q4(b)(iv) (1 mark): Pentane C5H12 36 –3509 Hexane C6H14 69 –4163 (iv) Use the data in Table 4.1 to estimate a value for the enthalpy change of combustion of butane. Give your answe
- June 2024, Paper 3, Q2(a)(iii) (2 marks): Hydrogen gas is being considered as a household fuel to replace methane. The enthalpy change of formation, ΔfH, for H2O(l) is –285.8 kJ mol–1. Determine the ene
- June 2024, AS Paper 2, Q3(a) (1 mark): What is meant by the term enthalpy change of reaction? [1]
- June 2023, AS Paper 1, Q11 (1 mark): The standard enthalpy change of formation of water is –286 kJ mol–1. Which statement or equation is correct? ΔH o = –143 kJ mol–1 A H2(g) + ½O2(g) H2O(l) ΔH o =
- June 2023, AS Paper 1, Q23(b)(i) (1 mark): State the conditions of temperature and pressure for standard enthalpy changes. Temperature Pressure [1]
- June 2023, AS Paper 2, Q4(a) (2 marks): Explain the term enthalpy change of combustion. [2]
- June 2022, Paper 1, Q17(b)(i) (1 mark): Explain the term enthalpy change of formation. [1]
- 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, Q25(a)(ii) (2 marks): The student looked back at Equation 25.1 and noticed that the reaction was a neutralisation. The student concluded that ∆rH is the enthalpy change of neutralisa
- November 2020, AS Paper 2, Q2(a) (2 marks): Explain the term enthalpy change of combustion, ΔcH. [2]
- June 2019, Paper 1, Q10 (1 mark): Radical reactions are responsible for the catalysed breakdown of the ozone layer. The overall equation is shown below. 3O2 ∆rH = −284 kJ mol−1 2O3 The molar gas
- June 2019, AS Paper 1, Q11 (1 mark): Hydrogen and chlorine react as shown below. H2(g) + Cl 2(g) → 2HCl (g) ∆H o = −184.6 kJ mol−1 Which statement about this reaction is correct? A Less energy is r
- June 2019, AS Paper 1, Q24(b)(i) (1 mark): State the conditions of temperature and pressure used for standard enthalpy measurements. Temperature Pressure [1]
- June 2018, AS Paper 2, Q3(d)(i) (1 mark): Write an equation, including state symbols, to represent the enthalpy change of vaporisation of bromine. [1]
- June 2018, AS Paper 2, Q4(a)(ii) (4 marks): 5.10 tonnes of NH3 are converted into NO. Calculate the energy released, in kJ, for this conversion. Give your answer in standard form and to an appropriate num
- June 2017, AS Paper 2, Q3(b)(i) (1 mark): The values for the first three alkanes are plotted on the graph below. Plot the value for butane on the graph. relative molecular mass 0 20 40 60 80 100 –1000 –
- June 2017, AS Paper 2, Q3(b)(ii) (3 marks): Use the graph to estimate the energy released during complete combustion of 1.80 g of pentane. Show relevant working below and on the graph. energy released = k
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