9.3 - Bond Enthalpies Flashcards Preview

OCR A Chemistry A Level - Chapter 9 > 9.3 - Bond Enthalpies > Flashcards

Flashcards in 9.3 - Bond Enthalpies Deck (5)
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1

Define average bond enthalpy

Average enthalpy change that takes place when breaking (by homolytic fission) one mole of a given type of bond in the gas state.

2

What are the characteristics of average bond enthalpies?

- Energy is always required to break bonds
- Bond enthalpy is always endothermic
- Bond enthalpy always has +ve delta H

3

What are the limitations of average bond enthalpy?

- Actual bond enthalpy relies on chemical environment
whereas aveage bond enthalpy averages actual bond enthalpies

4

Bond breaking and making, exo- or endo- thermic?

Breaking - Endo
Making - Exo

5

For a reaction involving gaseous molecules of covalent substances when calculating energy change from average bond enthalpies..

Enthalpy change of reaction =
Sum of bond enthalpies in reactants - sum of bond enthalpies in products