Chemical energetics: past paper questions
Real questions on chemical energetics
The newest 20 of 251 written questions, plus 1 multiple-choice. Open one to see it on the real paper.
- 9701/41 · May/June 2026 · Q1e[3]
Magnesium carbonate, MgCO 3 , decomposes when heated. MgCO 3 MgO + CO 2 ΔS = +175 J K –1 mol –1 ΔH = +117 kJ mol –1 Predict whether the decomposition of MgCO 3 is feasible at 600 °C. Use a calculation to explain your answer. feasibility explanation
See it on the paper → - 9701/41 · May/June 2026 · Q1f[2]
Calcium carbonate, CaCO 3 , also decomposes when heated. State whether the decomposition of CaCO 3 occurs at a higher or lower temperature than that of MgCO 3 . Explain your answer.
See it on the paper → - 9701/41 · May/June 2026 · Q4a[1]
Complete the equation that can be used to calculate the standard Gibbs free energy change, ΔG ⦵ , for a cell reaction using the standard cell potential, E ⦵ cell . ΔG =
See it on the paper → - 9701/41 · October/November 2025 · Q1c(i)[1]
Define enthalpy change of hydration, ΔH hyd . (c) (i)
See it on the paper → - 9701/41 · October/November 2025 · Q1c(ii)[2]
State the main factors that affect the magnitude of enthalpy change of hydration. Explain your answer.
See it on the paper → - 9701/41 · October/November 2025 · Q1d[2]
Table 1.1 energy change value / kJ mol –1 lattice energy of MgF 2 –2957 enthalpy change of hydration, ΔH hyd , of Mg 2+ –1926 enthalpy change of hydration, ΔH hyd , of F – –505 Use data from Table 1.1 to calculate the enthalpy change of solution, ΔH sol , for MgF 2 (s). (d) Table 1.1 shows various energy changes. ΔH so...
See it on the paper → - 9701/42 · October/November 2025 · Q1b[2]
State which of Mg(NO 3 ) 2 or Sr(NO 3 ) 2 decomposes at a lower temperature. Explain your answer. compound that decomposes at a lower temperature explanation
See it on the paper → - 9701/42 · October/November 2025 · Q1c(ii)[3]
Explain why A is more soluble than B.
See it on the paper → - 9701/42 · October/November 2025 · Q3d(i)[1]
Calculate the concentration of a saturated solution of Mn(OH) 2 at 298 K. [Mn(OH) 2 ] = mol dm –3
See it on the paper → - 9701/42 · October/November 2025 · Q3d(ii)[2]
Write an expression for the K sp of Mn(OH) 2 . Give the units of K sp . K sp =
See it on the paper → - 9701/42 · October/November 2025 · Q3d(iii)[1]
Use your answers to (d)(i) and (d)(ii) to calculate the value of K sp of Mn(OH) 2 at 298 K. K sp =
See it on the paper → - 9701/43 · October/November 2025 · Q1a(ii)[2]
The thermal stability of Group 2 carbonates increases down the group. Explain this trend.
See it on the paper → - 9701/43 · October/November 2025 · Q1b[4]
The hydroxides and fluorides of Group 2 elements show similar trends in solubility. Describe the trend in the solubility of the fluorides of calcium, strontium and barium. Explain your answer. least soluble most soluble explanation
See it on the paper → - 9701/43 · October/November 2025 · Q1c(i)[1]
Define enthalpy change of hydration, ΔH hyd . (c) (i)
See it on the paper → - 9701/43 · October/November 2025 · Q1c(ii)[2]
State the main factors that affect the magnitude of enthalpy change of hydration. Explain your answer.
See it on the paper → - 9701/43 · October/November 2025 · Q1d[2]
Table 1.1 energy change value / kJ mol –1 lattice energy of MgF 2 –2957 enthalpy change of hydration, ΔH hyd , of Mg 2+ –1926 enthalpy change of hydration, ΔH hyd , of F – –505 Use data from Table 1.1 to calculate the enthalpy change of solution, ΔH sol , for MgF 2 (s). (d) Table 1.1 shows various energy changes. ΔH so...
See it on the paper → - 9701/51 · October/November 2025 · Q1d(iii)[2]
Calculate the value of x in the formula BaCl 2 •xH 2 O. x =
See it on the paper → - 9701/53 · October/November 2025 · Q1d(iii)[2]
Calculate the value of x in the formula BaCl 2 •xH 2 O. x =
See it on the paper → - 9701/53 · October/November 2025 · Q1e[3]
Another student uses a different experimental method to check the value of x obtained by the method described in (b). Give a brief description of another method, not involving titration, that could be used to determine the value of x in the formula BaCl 2 •xH 2 O(s). Write your answer using a series of numbered steps....
See it on the paper → - 9701/23 · May/June 2025 · Q2c(ii)[2]
A student suggests the following hypothesis. The melting point of an ionically bonded oxide is only determined by the charge on the cation. Use Table 2.1 to deduce if this hypothesis is true or false or if there is not enough information to make a conclusion. Explain your answer.
See it on the paper →
What examiners said
This was generally well answered. Common errors were: • omitting ‘1 mole’ with ‘ionic compound formed’ • starting from 1 mole of gaseous ions.
— Examiner report, February/March 2025, 9701/42 Q1(b)(ii) (Cambridge)
Most candidates correctly calculated the enthalpy change of solution of AgF(s). A common error was –1925.
— Examiner report, February/March 2025, 9701/42 Q1(c)(i) (Cambridge)
Most candidates explained correctly that the negative Hsol would make AgF soluble in water. Some candidates gained credit by error carried forward being applied to their answer from (c)(i).
— Examiner report, February/March 2025, 9701/42 Q1(c)(ii) (Cambridge)
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