Enthalpy change, ΔH: past paper questions
Real questions on enthalpy change, δh
The newest 20 of 311 written questions. Open one to see it on the real paper.
- 9701/41 · May/June 2026 · Q1a[2]
Write the equation to represent the lattice energy, ΔH latt , of calcium sulfide, CaS. Include state symbols.
See it on the paper → - 9701/41 · May/June 2026 · Q1b[1]
Explain why the value of ΔH latt of CaS is negative.
See it on the paper → - 9701/41 · May/June 2026 · Q1c[3]
State the order of the ΔH latt values of CaS, MgO and KCl, from most negative to least negative. Explain your answer. most negative least negative explanation
See it on the paper → - 9701/41 · May/June 2026 · Q1d(i)[1]
The enthalpy change of formation of Cl – (g) can be calculated using two energy changes only. Identify the two energy changes.
See it on the paper → - 9701/41 · May/June 2026 · Q1d(ii)[2]
The lattice energy of magnesium chloride, MgCl 2 , is –2493 kJ mol –1 . Use this value, and other data given, to calculate the enthalpy change of formation, in kJ mol –1 , of MgCl 2 (s). ΔH f of MgCl 2 (s) = kJ mol –1
See it on the paper → - 9701/21 · October/November 2025 · Q3d(ii)[2]
Use the data in Fig. 3.2 and in Table 3.1 to calculate the enthalpy change of reaction 2, ΔH 2 . Table 3.1 compound enthalpy change of combustion, ΔH c / kJ mol –1 –3292 –3115 –286 H 2 ΔH 2 = kJ mol –1
See it on the paper → - 9701/22 · October/November 2025 · Q3e(ii)[2]
Use the data in Fig. 3.2 and in Table 3.1 to calculate the enthalpy change of reaction 2, ΔH 2 . Table 3.1 compound enthalpy change of formation, ∆H f / kJ mol −1 −156 +48 ΔH 2 = kJ mol –1
See it on the paper → - 9701/22 · October/November 2025 · Q3e(iii)[1]
Write an equation for the complete combustion of hexane.
See it on the paper → - 9701/23 · October/November 2025 · Q3d(ii)[2]
Use the data in Fig. 3.2 and in Table 3.1 to calculate the enthalpy change of reaction 2, ΔH 2 . Table 3.1 compound enthalpy change of combustion, ΔH c / kJ mol –1 –3292 –3115 –286 H 2 ΔH 2 = kJ mol –1
See it on the paper → - 9701/42 · October/November 2025 · Q1a[1]
Write an equation for the thermal decomposition of Mg(NO 3 ) 2 .
See it on the paper → - 9701/42 · October/November 2025 · Q4a[1]
Define enthalpy change of atomisation, ΔH at .
See it on the paper → - 9701/42 · October/November 2025 · Q4d[2]
The enthalpy change for the reaction Cl 2 (g) + 2e – 2Cl – (g) is – 486 kJ mol –1 . The first electron affinity of chlorine is –364 kJ mol –1 . Calculate the enthalpy change of atomisation of chlorine. ΔH at of chlorine = kJ mol –1
See it on the paper → - 9701/22 · May/June 2025 · Q3c[2]
Hydrocarbon Y contains two C=C groups. There are no other functional groups present. Y reacts with an excess of H 2 (g) to produce hexane, C 6 H 14 . Table 3.1 bond energy / kJ mol –1 C−C 350 C=C 610 C≡C 840 H−H 436 C−H 410 Use Table 3.1 to calculate the enthalpy change per mole of C 6 H 14 produced in this reaction. e...
See it on the paper → - 9701/22 · May/June 2025 · Q3d(i)[1]
Annotate Fig. 3.3 to show the effect of adding nickel to Y and H 2 (g) at temperature T.
See it on the paper → - 9701/41 · May/June 2025 · Q1a[1]
Write an equation for the thermal decomposition of CaCO 3 .
See it on the paper → - 9701/41 · May/June 2025 · Q1b[2]
State which of CaCO 3 and BaCO 3 decomposes at a lower temperature. Explain your answer. The compound that decomposes at a lower temperature is . explanation
See it on the paper → - 9701/41 · May/June 2025 · Q4a(i)[1]
Define enthalpy change of hydration.
See it on the paper → - 9701/41 · May/June 2025 · Q4a(ii)[2]
Explain the relative magnitudes of the enthalpy changes of hydration of K + and Ca 2+ .
See it on the paper → - 9701/43 · May/June 2025 · Q1a[1]
Write an equation for the thermal decomposition of CaCO 3 .
See it on the paper → - 9701/43 · May/June 2025 · Q1b[2]
State which of CaCO 3 and BaCO 3 decomposes at a lower temperature. Explain your answer. The compound that decomposes at a lower temperature is . explanation
See it on the paper →
What examiners said
The best answers were able to reference the isotopic abundance of chlorine and link this to the relative peak height shown in the mass spectrum. There was a high occurrence of referencing the [M + 1]+ peak, erroneously.
— Examiner report, February/March 2025, 9701/22 Q1(d)(i) (Cambridge)
Most candidates gave the correct equation for the standard enthalpy change of atomisation of silver, including the correct state symbols. However, the enthalpy change of formation of silver fluoride was less well known and many candidates did not realise that one mole of silver fluoride was required as the product. Some candidates thought that silver fluoride was formed from its ions.
— Examiner report, February/March 2025, 9701/42 Q1(b)(i) (Cambridge)
Candidates performed well on this question. Common errors included –308.5 (use of 79÷2), –269 (omission of 79) and –696 (use of 2 moles).
— Examiner report, February/March 2025, 9701/42 Q1(b)(iii) (Cambridge)
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