Chemical energetics: past paper questions

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• Question 14May/June 2026, paper 11Multiple choice1 markHas a diagram

  Some bond energies are given in the table.

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• Question 14Oct/Nov 2025, paper 11Multiple choice1 markHas a diagram

  Some bond energy data are given in the table.

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• Question 13Oct/Nov 2024, paper 11Multiple choice1 mark

  Which statement about exothermic and endothermic reactions is correct?

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• Question 14Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  Under certain conditions, nitrogen reacts with oxygen to form ${\mathrm{N}}_2\mathrm{O}$. $$2{\mathrm{N}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2{\mathrm{N}}_2\mathrm{O}(\mathrm{g})$$ The reaction pathway diagram is shown. What is the activation energy of the reverse reaction?

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• Question 12May/June 2026, paper 12Multiple choice1 markHas a diagram

  Which row about endothermic reactions is correct?

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

  Which statement about reactions is correct?

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• Question 15Oct/Nov 2024, paper 12Multiple choice1 markHas a diagram

  When chemical reaction X takes place, thermal energy is given out. Which row is correct for this reaction?

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• Question 15Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  Hydrogen and bromine react to form hydrogen bromide. $${\mathrm{H}}_2+\mathrm{B}{\mathrm{r}}_2\to 2\mathrm{H}\mathrm{B}\mathrm{r}$$ Bond energy data is given in the table.

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• Question 14May/June 2026, paper 12Multiple choice1 markHas a diagram

  The reaction pathway diagram for both the catalysed and uncatalysed reactions between ${\text{N}}_2$ and ${\text{H}}_2$ in the Haber process is shown. What is the activation energy for the formation of ${\text{NH}}_3$ in the presence of a catalyst?

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• Question 13Oct/Nov 2025, paper 12Multiple choice1 markHas a diagram

  The word equations for two reactions of ethene are shown.

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• Question 2Oct/Nov 2024, paper 21Structured15 marksHas a diagram

  Iron is extracted in a blast furnace by the reduction of iron(III) oxide with carbon monoxide. $${\text{Fe}}_2{\text{O}}_3+3\text{CO}\to 2\text{Fe}+3{\text{CO}}_2$$ This reaction is a redox reaction. State the meaning of the term redox reaction.

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• Question 13Oct/Nov 2023, paper 12Multiple choice1 markHas a diagram

  Hydrogen reacts with chlorine to form hydrogen chloride. $${\text{H}}_2\text{(g)}+{\text{Cl}}_2\text{(g)}\to 2\text{HCl(g)}$$ The enthalpy change, $\mathrm{\Delta }H$, for this reaction can be calculated using bond energies.

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• Question 3May/June 2026, paper 21Structured10 marksHas a diagram

  Hydrogen reacts with oxygen to make water. $$2{\mathrm{H}}_2(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\to 2{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$ Figure 3.1 shows the reaction pathway diagram for this reaction. The reaction is exothermic.

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• Question 3Oct/Nov 2025, paper 21Structured7 marksHas a diagram

  Sodium hydrogencarbonate decomposes when heated.

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• Question 4Oct/Nov 2024, paper 21Structured14 marksHas a diagram

  This question is about alkanes and alkenes. But-1-ene belongs to the alkene homologous series. Members of the same homologous series differ from one member to the next by a –CH${}_2$– group and have similar chemical properties.

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• Question 14Oct/Nov 2023, paper 12Multiple choice1 mark

  Nitrogen and oxygen react as shown. $${\text{N}}_2\text{(g)}+2{\text{O}}_2\text{(g)}\to 2{\text{NO}}_2\text{(g)}$$ The enthalpy change for the reaction shown is $+66\text{ kJ}$. If two moles of nitrogen and two moles of oxygen are used, what will be the enthalpy change?

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• Question 3May/June 2026, paper 22Structured9 marksHas a diagram

  The equation for one of the reactions that happens in a catalytic converter is shown. $$2\mathrm{N}\mathrm{O}(\mathrm{g})\to {\mathrm{O}}_2(\mathrm{g})+{\mathrm{N}}_2(\mathrm{g})$$ This decomposition reaction is exothermic.

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• Question 3Oct/Nov 2025, paper 22Structured7 marksHas a diagram

  The equation for the reaction between aluminium and dilute hydrochloric acid is shown. $$2\mathrm{A}\mathrm{l}(\mathrm{s})+6\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})\to 2{\mathrm{A}\mathrm{l}\mathrm{C}\mathrm{l}}_3(\mathrm{a}\mathrm{q})+3{\mathrm{H}}_2(\mathrm{g})$$ Fig. 3.1 shows the reaction pathway diagram for this reaction.

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• Question 4Oct/Nov 2024, paper 22Structured13 marksHas a diagram

  This question is about alkanes and alkenes. Butane belongs to the alkane homologous series. Members of the same homologous series have the same functional group and the same general formula.

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• Question 6Oct/Nov 2023, paper 21Structured7 marks

  The equation for the Haber process used in the production of ammonia is shown. $${\mathrm{N}}_2+3{\mathrm{H}}_2\rightleftharpoons 2{\mathrm{N}\mathrm{H}}_3$$ The nitrogen for this process comes from the air. State the percentage by volume of nitrogen in clean, dry air.

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• Question 7May/June 2026, paper 22Structured9 marks

  Chloroethene is a monomer used to make poly(chloroethene). The displayed formula of chloroethene is shown. Draw the structure of poly(chloroethene).

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• Question 4Oct/Nov 2025, paper 41Essay6 marksHas a diagram

  Alcohols are used as fuels to heat water. Plan an experiment to determine which alcohol, methanol or ethanol, releases more thermal energy per gram of alcohol burned.

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• Question 14May/June 2024, paper 11Multiple choice1 mark

  Ammonium nitrate dissolves in water. $$\mathrm{N}{\mathrm{H}}_4\mathrm{N}{\mathrm{O}}_3(\mathrm{s})\stackrel{{\mathrm{H}}_2\mathrm{O}}{\to }\mathrm{N}{\mathrm{H}}_4\mathrm{N}{\mathrm{O}}_3(\mathrm{a}\mathrm{q})\mathrm{\Delta }H=+25\text{ kJ}\mathrm{/}\text{mol}$$ Which statements are correct?

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• Question 6Oct/Nov 2023, paper 22Structured7 marks

  Steam reacts with carbon to produce carbon monoxide and hydrogen. $$\text{steam}+\text{carbon}\rightleftharpoons \text{carbon monoxide}+\text{hydrogen}$$ The forward reaction is endothermic.

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• Question 4May/June 2026, paper 41Essay6 marks

  When salt is added to ice, the temperature of the mixture decreases. A student suggests that the greater the mass of salt that is mixed with ice the more the temperature of the mixture decreases. Plan an investigation to find out if the student is correct.

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• Question 4Oct/Nov 2025, paper 42Essay6 marks

  The reaction between a metal and dilute sulfuric acid is exothermic. Plan an experiment to determine which metal, magnesium or zinc, releases more thermal energy per gram of metal when reacting with excess dilute sulfuric acid.

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• Question 15May/June 2024, paper 11Multiple choice1 markHas a diagram

  Hydrogen reacts with oxygen to produce water. $$\begin{array}{c}\mathrm{H}-\mathrm{H}\\ \mathrm{H}-\mathrm{H}\end{array}+\mathrm{O}=\mathrm{O}\to \begin{array}{c}\mathrm{H}-\mathrm{O}-\mathrm{H}\\ \mathrm{H}-\mathrm{O}-\mathrm{H}\end{array}$$ Some bond energies are shown.

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• Question 2Oct/Nov 2023, paper 41Structured14 marksHas a diagram

  Hydrochloric acid, $\mathrm{H}\mathrm{C}\mathrm{l}$, is neutralised when it is added to aqueous potassium hydroxide, $\mathrm{K}\mathrm{O}\mathrm{H}$. $$\mathrm{K}\mathrm{O}\mathrm{H}+\mathrm{H}\mathrm{C}\mathrm{l}\to \mathrm{K}\mathrm{C}\mathrm{l}+{\mathrm{H}}_2\mathrm{O}$$ The reaction is exothermic. $\mathbf{P}$ is aqueous potassium hydroxide.

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• Question 16May/June 2025, paper 11Multiple choice1 markHas a diagram

  Which row is correct for a chemical reaction in which $\mathrm{\Delta }H$ is negative?

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• Question 1May/June 2024, paper 12Multiple choice1 mark

  Which physical changes are both exothermic?

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