Gibbs free energy change, ΔG: past paper questions

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• Question 1May/June 2026, paper 41Structured14 marks

  Write the equation to represent the lattice energy, $\mathrm{\Delta }{H}_{\text{latt}}$, of calcium sulfide, $\text{CaS}$.

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• Question 2Oct/Nov 2025, paper 41Structured8 marks

  Iron can form stable ions in the +2 and +3 oxidation states. Explain why transition elements have variable oxidation states.

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• Question 2Oct/Nov 2024, paper 42Structured14 marksHas a diagram

  Predict and explain the variation in enthalpy change of hydration for the ions ${\text{Na}}^{+}$, ${\text{Mg}}^{2+}$ and ${\text{Al}}^{3+}$.

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• Question 3Oct/Nov 2023, paper 41Structured17 marksHas a diagram

  Hydrogen peroxide is a liquid at $298\mathrm{K}$. It is moderately stable under room conditions but will decompose quickly if a catalyst is added. $$\text{reaction 1}2{\mathrm{H}}_2{\mathrm{O}}_2(\mathrm{l})\to 2{\mathrm{H}}_2\mathrm{O}(\mathrm{l})+{\mathrm{O}}_2(\mathrm{g})$$ Define entropy.

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• Question 4May/June 2026, paper 41Structured10 marksHas a diagram

  Some electrode potentials are given in Table 4.1.

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• Question 2Oct/Nov 2024, paper 43Structured14 marksHas a diagram

  Predict and explain the variation in enthalpy change of hydration for the ions ${\mathrm{F}}^{-}$, ${\mathrm{C}\mathrm{l}}^{-}$, ${\mathrm{B}\mathrm{r}}^{-}$ and ${\mathrm{I}}^{-}$.

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• Question 3Oct/Nov 2023, paper 42Structured18 marksHas a diagram

  Some electrode potentials are shown in Table 3.1.

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• Question 3May/June 2024, paper 42Structured5 marks

  Carbon disulfide, ${\text{CS}}_2$, is flammable and reacts readily with oxygen, as shown in reaction 1.

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• Question 3Oct/Nov 2023, paper 43Structured17 marksHas a diagram

  Hydrogen peroxide is a liquid at $298\mathrm{K}$. It is moderately stable under room conditions but will decompose quickly if a catalyst is added. $$\text{reaction 1}2{\mathrm{H}}_2{\mathrm{O}}_2(\mathrm{l})\to 2{\mathrm{H}}_2\mathrm{O}(\mathrm{l})+{\mathrm{O}}_2(\mathrm{g})$$ Define entropy.

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• Question 3May/June 2025, paper 42Structured8 marksHas a diagram

  Define entropy.

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• Question 5May/June 2023, paper 41Structured13 marks

  The exhaust systems of most modern gasoline-fuelled cars contain a catalytic converter with three metal catalysts. These metals act as heterogeneous catalysts. Name three metal catalysts used in catalytic converters.

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• Question 4May/June 2025, paper 43Structured8 marks

  Table 4.1 gives the enthalpy changes of hydration, $\mathrm{\Delta }{H}_{\text{hyd}}$, of three ions, ${\mathrm{F}}^{-}$, ${\mathrm{K}}^{+}$ and ${\mathrm{C}\mathrm{a}}^{2+}$.

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• Question 3May/June 2023, paper 42Structured12 marks

  Complete Table 3.1 by placing one tick (✓) in each row to indicate the sign of each type of energy change under standard conditions.

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