9.3 Bond enthalphies
No description yet. This curated deck is ready for daily study.
Card preview (10)
What is average bond enthalpy
The energy required to break one mole of a specified type of bond in a gaseous molecule
What is always needed to break bonds
Energy
Are bond enthalpies always exothermic or endothermic
Endothermic
Do bond enthalpies always have a positive or negative enthalpy value
Positive
Is breaking bonds endothermic or exothermic
Endothermic Energy is required ΔH is positive
Is making bonds endothermic or exothermic
Exothermic Energy is released ΔH is negative
What determines whether or not a reaction is exothermic or endothermic overall
The difference between energy required for bond breaking and the energy released by bond making
How can the enthalpy change of reaction ΔrH ne found
By calculating the bond enthalpies of the bonds in the reactants and the products
For a reaction involving gaseous molecules of covalent substances:
ΔrH = Σ(bond enthalpies in reactants) - Σ(bond enthalpies in products)
Why are there limitations in the calculated enthalpy change
Bonds may be different in different environments, however, the calculated enthalpy change of reaction should be in general agreement with the actual enthalpy change of reaction