3.2.1 Bond Enthalpy Flashcards
define average bond enthalpy
average bond enthalpy is the average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species
what is always required to break bonds
Energy is always required to break bonds, therefore bond enthalpies are always endothermic and have positive enthalpy values.
how is average bond enthalpy calculated
it is calculated from the actual bond enthalpies in different chemical enviroments
how do you calculate 𝚫H from average bond enthalpies
𝚫Hr = 𝚺(bond enthalpies in reactants) - 𝚺(bond enthalpies in products)
𝚺 = sum of
when are bonds endothermic and exothermic
Breaking bonds is endothermic (energy is needed and taken in from the surroundings)
Making bonds is exothermic (energy is released to the surroundings)
what is 𝚫H
𝚫H is the difference between the energy used to break bonds and the energy released making bonds
What is a limitation of using average bond enthalpies in calculations
The actual energy involved in breaking and making bonds would be slightly different. Despite this the calculated enthalpy change of reaction should be in general agreement with the actual enthalpy change of reaction.
