Enthalpy change, ΔH: past paper questions

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• Question 8May/June 2026, paper 11Multiple choice1 mark

  The equation for a reaction is shown. $$\text{C(s)}+{\text{CO}}_2\text{(g)}\to 2\text{CO(g)}$$ This reaction has an enthalpy change of $+172{\text{ kJ mol}}^{-1}$. Which deduction can be made from this information?

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• Question 7Oct/Nov 2025, paper 11Multiple choice1 mark

  When $1.0\text{ mol}$ of ethanoic acid, ${\text{CH}}_3\text{COOH}$, in aqueous solution is neutralised by an excess of aqueous sodium hydroxide, $55\text{ kJ}{\text{mol}}^{-1}$ of energy is released. Which statement about this reaction is correct?

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• Question 9Oct/Nov 2024, paper 11Multiple choice1 mark

  The standard enthalpy change of combustion of carbon is $-394{\text{ kJ mol}}^{-1}$. The standard enthalpy change of combustion of hydrogen is $-286{\text{ kJ mol}}^{-1}$. The standard enthalpy change of formation of butane is $-129{\text{ kJ mol}}^{-1}$.

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• Question 9Oct/Nov 2023, paper 11Multiple choice1 mark

  Which statement about enthalpy changes is correct?

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• Question 9May/June 2026, paper 12Multiple choice1 mark

  An energy cycle is shown.

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• Question 8Oct/Nov 2025, paper 11Multiple choice1 mark

  In an experiment, $1.60\text{ g}$ of a fuel is burnt. $45.0\mathrm{\%}$ of the energy released is absorbed by $200\text{ g}$ of water. The temperature of the water rises from $18.0{}^{\circ }\text{C}$ to $66.0{}^{\circ }\text{C}$.

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• Question 10Oct/Nov 2024, paper 11Multiple choice1 mark

  Three processes are described.

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• Question 10May/June 2026, paper 12Multiple choice1 mark

  $50{\text{ cm}}^3$ of $2.50{\text{ mol dm}}^{-3}$ hydrochloric acid was placed in a polystyrene beaker of negligible heat capacity.

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• Question 9Oct/Nov 2025, paper 12Multiple choice1 mark

  When $0.47\text{ g}$ of a hydrocarbon is completely burnt in air, the energy released heats $200\text{ g}$ of water from $23.7{}^{\circ }\text{C}$ to $41.0{}^{\circ }\text{C}$. What is the amount of energy absorbed, in Joules, by the water?

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• Question 9Oct/Nov 2024, paper 12Multiple choice1 mark

  For which reaction is the enthalpy change an enthalpy change of formation?

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• Question 8May/June 2026, paper 13Multiple choice1 markHas a diagram

  Bond energy data can be used to calculate the enthalpy change of a reaction.

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• Question 10Oct/Nov 2025, paper 12Multiple choice1 mark

  One commercially available 'heat pad' contains iron, activated carbon and water. The 'heat pad' is activated by air. This causes the pad to get hotter.

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• Question 3May/June 2026, paper 23Structured13 marksHas a diagram

  The conditions used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process are carefully controlled.

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• Question 15Oct/Nov 2025, paper 12Multiple choice1 markHas a diagram

  Which reaction pathway diagram shows an endothermic reaction that occurs in two steps and in which the second step of the reaction is likely to be faster than the first?

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• Question 9May/June 2024, paper 11Multiple choice1 markHas a diagram

  An energy cycle is shown. The energy changes involved are X, Y and Z. The numerical value of energy change Y is either $-890$ or $+890$. The numerical value of energy change Z is either $-964$ or $+964$.

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• Question 15Oct/Nov 2023, paper 13Multiple choice1 mark

  The forward reaction of a reversible reaction is exothermic and has an activation energy of $+30{\text{ kJ mol}}^{-1}$. The reverse reaction proceeds by a mechanism that is the exact reverse of the mechanism of the forward reaction.

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• Question 7Oct/Nov 2025, paper 13Multiple choice1 mark

  When $1.0\text{ mol}$ of ethanoic acid, ${\text{CH}}_3\text{COOH}$, in aqueous solution is neutralised by an excess of aqueous sodium hydroxide, $55\text{ kJ}{\text{mol}}^{-1}$ of energy is released. Which statement about this reaction is correct?

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• Question 10May/June 2024, paper 11Multiple choice1 markHas a diagram

  For a certain endothermic reaction, the activation energy is numerically equal to twice the enthalpy change of reaction. Which reaction pathway diagram is correct for this reaction?

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• Question 1Oct/Nov 2023, paper 21Structured22 marksHas a diagram

  The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl. The first ionisation energy of S is not shown.

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• Question 9May/June 2024, paper 12Multiple choice1 markHas a diagram

  Ethane can react with fluorine to produce 1,2-difluoroethane, ${\text{C}}_2{\text{H}}_4{\text{F}}_2$.

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• Question 3Oct/Nov 2023, paper 22Structured19 marksHas a diagram

  Phosphoric(V) acid, ${\mathrm{H}}_3{\mathrm{P}\mathrm{O}}_4$, is used in both inorganic and organic reactions. ${\mathrm{H}}_3{\mathrm{P}\mathrm{O}}_4$ is made in a two-step process from phosphorus. step 1 Phosphorus reacts with an excess of oxygen to form a white solid.

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• Question 5May/June 2025, paper 11Multiple choice1 markHas a diagram

  The reaction of hydrogen with oxygen is shown. $$2{\text{H}}_2(\text{g})+{\text{O}}_2(\text{g})\to 2{\text{H}}_2\text{O}(\text{l})$$ Which expression corresponds to the standard enthalpy change of this reaction?

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• Question 10May/June 2024, paper 12Multiple choice1 mark

  Which equation has an enthalpy change equal to the standard enthalpy of formation of sodium oxide?

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• Question 11May/June 2025, paper 11Multiple choice1 mark

  $50{\text{ cm}}^3$ of $1.0\text{ mol}{\text{dm}}^{-3}{\text{ H}}_2{\text{SO}}_4$ is added to $100{\text{ cm}}^3$ of $1.0\text{ mol}{\text{dm}}^{-3}\text{ NaOH}$ in an insulated vessel. Both solutions are at a temperature of $20{}^{\circ }\text{C}$ before mixing.

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• Question 9May/June 2024, paper 13Multiple choice1 markHas a diagram

  The apparatus used to determine a value for the enthalpy of combustion of butan-1-ol is shown.

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• Question 13May/June 2025, paper 12Multiple choice1 markHas a diagram

  Under certain conditions, $\mathrm{C}\mathrm{C}{\mathrm{l}}_4$ and ${\mathrm{H}}_2\mathrm{O}$ react as shown. The activation energy for the reaction is $+62{\text{ kJ mol}}^{-1}$.

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• Question 10May/June 2024, paper 13Multiple choice1 markHas a diagram

  In the high temperatures of car engines, nitrogen reacts with oxygen to produce nitrogen monoxide.

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• Question 10May/June 2023, paper 12Multiple choice1 mark

  Nitrogen monoxide is rapidly oxidised to nitrogen dioxide. $$2\text{NO}(\text{g})+{\text{O}}_2(\text{g})\to 2{\text{NO}}_2(\text{g})$$ Nitrogen dioxide can then dimerise to form dinitrogen tetroxide.

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• Question 12May/June 2025, paper 13Multiple choice1 mark

  The equation for the reaction of nitrogen with hydrogen is shown. $${\text{N}}_2(\text{g})+3{\text{H}}_2(\text{g})\rightleftharpoons 2{\text{NH}}_3(\text{g})\mathrm{\Delta }{H}_{\text{r}}^{\circ }=-92.2\text{kJ}{\text{mol}}^{-1}$$ Which statement is correct?

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• Question 4May/June 2024, paper 21Structured6 marks

  Define enthalpy change of formation.

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