Question detail
When constructing a Born-Haber cycle, how is the enthalpy of formation of the ionic compound used?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Thermodynamics (A-level only)
Question
- A. As a negative value in the cycle
- B. As a positive value in the cycle
- C. It is not used
- D. As the final step in the cycle
Answer
As a negative value in the cycle
Explanation
The enthalpy of formation is used as a negative value in the Born-Haber cycle because it represents the energy released when the compound is formed from its elements.
Common mistake
Incorrect Born-Haber Cycle Construction
Students often forget to include all relevant enthalpy changes, such as sublimation and ionization energies, when constructing Born-Haber cycles.
To correctly construct a Born-Haber cycle, include all necessary enthalpy changes: the enthalpy of formation, sublimation, ionization, and electron affinity. For example, use the formula: ΔH_f = ΔH_sublimation + ΔH_ionization + ΔH_electron_affinity + ΔH_lattice. Substitute the values for each enthalpy change, perform the calculations, and ensure all steps are represented in the cycle.
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