Chemical energetics: past paper questions
Real questions on chemical energetics
The newest 20 of 66 written questions, plus 36 multiple-choice. Open one to see it on the real paper.
- 5070/22 · October/November 2025 · Q3a(i)[2]
Identify the energy changes labelled A and B. energy change A (i)
See it on the paper → - 5070/22 · October/November 2025 · Q3a(ii)[1]
Use the reaction pathway diagram to explain why the reaction is exothermic.
See it on the paper → - 5070/42 · October/November 2025 · Q4[6]
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. You are provided with magnesium powder, zinc powder, dilute sulfuric acid and common laborat...
See it on the paper → - 5070/21 · May/June 2025 · Q3c[3]
Table 3.1 shows some bond energies. C—H 410 C—Cl 340 Cl —Cl 242 H—Cl 431 Show by calculation that the enthalpy change of the reaction between methane and chlorine, ΔH, is –119 kJ / mol. bond energy in kJ / mol bond Table 3.1
See it on the paper → - 5070/21 · May/June 2025 · Q3d[3]
Complete the reaction pathway diagram in Fig. 3.2 for the reaction between methane and chlorine. Label the: • • • • reactants products enthalpy change of the reaction, ΔH activation energy, E a . energy progress of reaction
See it on the paper → - 5070/21 · October/November 2024 · Q4e(i)[3]
Calculate the enthalpy change of this reaction in kJ / mol. Use the bond energies in Table 4.1. Table 4.1 type of bond C=C C–H Br–Br C–C C–Br bond energy in kJ / mol 612 413 193 347 290
See it on the paper → - 5070/21 · October/November 2024 · Q4e(ii)[1]
Describe the colour change when a sample of excess ethene is added to a few drops of aqueous bromine. from to
See it on the paper → - 5070/22 · October/November 2024 · Q4d(iii)[3]
Calculate the enthalpy change of this reaction in kJ / mol. Table 4.1 C–C C–H Cl –Cl C–Cl H–Cl bond energy in kJ / mol 347 413 243 346 432 type of bond Use the bond energies in Table 4.1.
See it on the paper → - 5070/22 · October/November 2024 · Q5d[3]
The reaction of zinc with hydrochloric acid is exothermic. Complete the reaction pathway diagram in Fig. 5.2 to show: the reactants and products a labelled arrow for the activation energy, E a a labelled arrow for the enthalpy change, ΔH. • • • energy progress of reaction
See it on the paper → - 5070/22 · May/June 2024 · Q2c(ii)[3]
Complete the reaction pathway diagram in Fig. 2.1 for the complete combustion of methane. Label the: • • • • reactants products enthalpy change of the reaction, ΔH activation energy, E a . energy progress of reaction Fig. 2.1
See it on the paper → - 5070/41 · May/June 2024 · Q2e[3]
State and explain the effect of using half the concentration of aqueous copper( II ) sulfate on the temperature increase for metal A. effect explanation
See it on the paper → - 5070/42 · May/June 2024 · Q2b[2]
Describe the energy change when the solid dissolves in water. Explain how the results in Table 2.1 support your answer. description explanation
See it on the paper → - 5070/21 · October/November 2023 · Q6b(ii)[1]
The transfer of thermal energy in a chemical reaction is called the enthalpy change. Write the symbol for an enthalpy change. Include the sign for an exothermic enthalpy change.
See it on the paper → - 5070/22 · October/November 2023 · Q6a(i)[2]
Explain, in terms of bond making and bond breaking, why this reaction is endothermic.
See it on the paper → - 5070/22 · October/November 2023 · Q6a(ii)[1]
The transfer of thermal energy in a chemical reaction is called the enthalpy change. Write the symbol for an enthalpy change. Include the sign for an endothermic enthalpy change.
See it on the paper → - 5070/22 · October/November 2023 · Q6b(i)[1]
Name one other substance formed during the incomplete combustion of carbon-containing fuels.
See it on the paper → - 5070/22 · October/November 2023 · Q6b(ii)[1]
State one adverse effect of carbon monoxide.
See it on the paper → - 5070/21 · May/June 2023 · Q6a[5]
Methane reacts with chlorine to make chloromethane. The reaction is exothermic. CH 4 (g) + Cl 2 (g) CH 3 Cl (g) + HCl (g) Draw, on the axes provided in Fig. 6.1, the reaction pathway diagram for this reaction. Include labels for the: • • • • • axes reactants products enthalpy change of reaction, ΔH activation energy, E...
See it on the paper → - 5070/21 · May/June 2023 · Q6b[3]
Hydrogen iodide decomposes to make hydrogen and iodine. 2H—I H—H + I—I Calculate the enthalpy change of this reaction. Use the bond energies in Table 6.1. Table 6.1 bond bond energy in kJ / mol H—H 436 I—I 151 H—I 298 enthalpy change of reaction kJ / mol
See it on the paper → - 5070/21 · May/June 2023 · Q10b(i)[1]
Some waste poly(propene) plastic is disposed of by burning. This makes a toxic gas because of incomplete combustion. Name this toxic gas.
See it on the paper →
What examiners said
The symbol was quite well known. Common incorrect responses included ∆H with no sign, ∆E and ∆H+. A small number omitted the question.
— Examiner report, October/November 2023, 5070/21 Q6(b)(ii) (Cambridge)
The best answers stated that bond breaking absorbs energy and bond making releases energy and then went on to state that more energy is absorbed than released. The most common misconception involved more energy needed for bond breaking than bond making.
— Examiner report, October/November 2023, 5070/22 Q6(a)(i) (Cambridge)
Candidates gave a wide range of answers for the symbol for an endothermic reaction including H+, H+, ∆H+, +∆H and ∆H>0. The best answers was ∆H = positive or +ve.
— Examiner report, October/November 2023, 5070/22 Q6(a)(ii) (Cambridge)
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