bond enthalpies

Cards (7)

what can mean bond enthalpies be used for?
to calculate an approx value for enthalpy change in reactions in the gaseous phase.
what do all chemical reactions involve?
breaking of reactants bonds and forming of new product bonds.
what is the definition for 'mean bond enthalpy'?
= amount of energy needed to break 1 mole of covalent bonds in a substance in a gaseous state, averaged over a range of compounds.
what are bond enthalpy values always? why?
positive, because bond breaking is endothermic as energy is needed to overcome forces of attraction between shared pair of electrons in the covalent bond and positive protons in the nucleus of each atom.
what is bond forming?
exothermic bc energy is released when bonds are made.
what does the difference between values of endothermic bond breaking process and exothermic bond forming process dictate? 
if a reaction is overall exothermic or endothermic.
what is equation for enthalpy change?
enthalpy change = bonds broken (reactants) - bonds formed (products)