plumiExothermic, endothermic and enthalpy profiles: OCR A‑Level Chemistry A questions
OCR A-Level Chemistry A past-paper questions on 3.2.1.1 Exothermic, endothermic and enthalpy profiles, 2016–2025, with mark schemes and examiner’s reports where available.
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Q4(b)(iii)
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Open the full PDFYour answerQ23(a)(ii)
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Open the full PDFYour answerQ20(b)
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All 10 questions on Exothermic, endothermic and enthalpy profiles, as a list
- June 2025, AS Paper 2, Q4(b)(iii) (2 marks): Complete the enthalpy profile diagram for the complete combustion of pentane. On your diagram: • Label the enthalpy change as ΔH. • Include the formulae of the
- June 2023, AS Paper 1, Q12 (1 mark): Which statement about energy changes is correct? A Combustion of an alkane is endothermic. B In an exothermic reaction, more energy is needed to break bonds tha
- June 2023, AS Paper 1, Q23(a)(ii) (2 marks): In a petrol engine, polluting gases such as CO and NO are formed. These are mostly removed before being emitted from the exhaust. The equation for the removal o
- June 2019, AS Paper 1, Q10 (1 mark): A reversible reaction has the enthalpy profile diagram shown below. 150 energy reactants /kJ mol–1 120 products progress of reaction Which statement about this
- 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 2018, Paper 1, Q20(b) (3 marks): Hydrogen iodide, HI, is decomposed by heat into its elements: 2HI(g) H2(g) + I2(g) ∆H = +9.5 kJ mol–1 The decomposition is much faster in the presence of a plat
- June 2018, AS Paper 2, Q3(d)(ii) (1 mark): Suggest whether the enthalpy change of vaporisation of bromine is exothermic or endothermic. Explain your answer. [1]
- June 2018, AS Paper 2, Q4(a)(i) (2 marks): Complete the enthalpy profile diagram for this reaction. On your diagram: • Label the activation energy, Ea • Label the enthalpy change of reaction, ∆H • Includ
- June 2016, AS Paper 2, Q4(a)(i) (1 mark): Explain, in terms of bond breaking and bond making, why the enthalpy change of formation of NO is endothermic. [1]
- June 2016, AS Paper 2, Q4(a)(ii) (2 marks): Draw a fully labelled enthalpy profile diagram to represent the enthalpy change of formation of N2O. The formulae, with state symbols, of the reactants and prod
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