Question detail
Why might mean bond enthalpy estimates not reflect the true energy changes in a reaction?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Energetics
Question
- A. They are based on average values from various compounds.
- B. They consider only gaseous reactants.
- C. They ignore the effects of temperature and pressure.
- D. They are calculated using theoretical models.
Answer
They are based on average values from various compounds.
Explanation
Mean bond enthalpy estimates are derived from average values across different molecules, which may not accurately represent the specific bonding environment in a given reaction. This averaging can overlook unique interactions and energy contributions present in the actual reactants and products. As a result, the calculated energy changes may not align with the true enthalpy changes observed in reactions, leading to potential inaccuracies in thermodynamic calculations.
Common mistake
Misunderstanding Mean Bond Enthalpy
Students often confuse mean bond enthalpy with the actual enthalpy changes calculated using Hess's law.
Mean bond enthalpy is an average value that does not account for the specific molecular environment of bonds in a reaction, leading to discrepancies when compared to Hess's law calculations, which consider the actual enthalpy changes for specific reactions.
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