CAIE A Level Chemistry 9701 · Chemical energetics
Limestone is largely calcium carbonate, . When heated strongly it decomposes into calcium oxide, , and carbon dioxide, .
The standard enthalpy changes of formation of , and are known.
Suggest how a simple Hess cycle could be used to determine the standard enthalpy change of this decomposition. Describe the two routes round the cycle and state how the decomposition enthalpy change is related to the enthalpy changes of formation.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
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