Hess’s law: past paper questions

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• Question 9May/June 2026, paper 11Multiple choice1 mark

  Sulfur can be oxidised to produce two different oxides.

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• Question 3Oct/Nov 2025, paper 22Structured14 marksHas a diagram

  The alkanes are a homologous series of organic molecules. Alkanes are generally unreactive and are commonly used as fuels. Define homologous series.

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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 11Oct/Nov 2023, paper 12Multiple choice1 mark

  Nitric acid is made industrially by the oxidation of ammonia. The overall equation for the process is shown. $$\text{equation 1}{\text{NH}}_3+2{\text{O}}_2\to {\text{HNO}}_3+{\text{H}}_2\text{O}$$ The process happens in three stages.

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

  An energy cycle is shown.

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• Question 6May/June 2025, paper 12Multiple choice1 markHas a diagram

  Some standard enthalpy of combustion data are given.

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• Question 10Oct/Nov 2024, paper 12Multiple choice1 mark

  Two standard enthalpy change of formation values are given.

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• Question 5May/June 2023, paper 11Multiple choice1 markHas a diagram

  Calcium carbide, $\mathrm{C}\mathrm{a}{\mathrm{C}}_2$, reacts with water, as shown. The data below the equation show, in $\mathrm{k}\mathrm{J}\mathrm{m}\mathrm{o}{\mathrm{l}}^{-1}$, the standard enthalpies of formation of the compounds involved.

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• Question 9May/June 2026, paper 13Multiple choice1 mark

  Sulfur can be oxidised in two ways.

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• Question 6May/June 2025, paper 13Multiple choice1 markHas a diagram

  The first stage in the industrial production of nitric acid from ammonia can be represented by the following equation.

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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 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 4May/June 2024, paper 21Structured6 marks

  Define enthalpy change of formation.

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• Question 2May/June 2024, paper 22Structured10 marksHas a diagram

  Separate samples of $\mathrm{N}{\mathrm{a}}_2\mathrm{C}{\mathrm{O}}_3$ and $\mathrm{N}\mathrm{a}\mathrm{H}\mathrm{C}{\mathrm{O}}_3$ react with $\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})$ to produce the same products, as shown in Table 2.1.

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• Question 3May/June 2024, paper 23Structured7 marks

  Write an equation to show the reaction for the standard enthalpy change of formation of ${\mathrm{H}}_2\mathrm{O}$.

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