bond enthalpies

Cards (6)

What is the definition of average bond enthalpy?
The mean energy required to break 1 mole of bonds in gaseous molecules, under standard conditions.
Why will using bond enthalpies not be as accurate as using standard enthalpy of combustion/formation?
Bond enthalpies are a mean for the same bond across different molecules, whereas standard enthalpy of combustion and formation apply to just that molecule, thus they are more accurate.
How do you calculate enthalpy change of reaction using average bond enthalpies?
^H = { (bond enthalpies of reaction) - { (bond enthalpies of products)
Why do bond enthalpies have positive values?
as bond breaking is endothermic -energy has to be put in to break a bond
Why will using bond enthalpies not be as accurate as using standard enthalpy of combustion/formation?
as bond enthalpies are a mean for the same bond across different molecules whereas standard enthalpy of combustion and formation just apply to that molecule thus is more accurate
How do you calculate enthalpy change of reaction using average bond enthalpies?
^H= sum of bond enthalpies of reactants - sum of bond enthalpies of products