A Born-Haber cycle differs from an enthalpy of formation in that the cycle:
Ameasures only the heat released on melting
Bbreaks the formation into separate energy steps
Capplies solely to organic combustion reactions
Dgives the heat change per litre of solution
Answer & Solution
Correct answer: B. breaks the formation into separate energy steps
1. The enthalpy of formation is a single value: the heat change when one mole of a compound forms from its elements.
2. A Born-Haber cycle is not a single value but a route.
3. It breaks that overall formation into separate steps — atomisation, ionisation, electron affinity, lattice energy.
4. Because energy is a state function, the steps must sum to the enthalpy of formation.
5. That is what makes the cycle useful: it lets an unmeasurable step such as lattice energy be found from the measurable ones.
_Source: NECTA ACSEE 2023 Chemistry 132/1, Question 6: Energetics_