5.3 Bond Energies

  • Bond dissociation energy: the amount of energy required to break a particular type of chemical bond in 1 mole of a substance.
    • None of the values are measured but rather experimentally calculated. They are purely theoretical.
  • Multiple bonds have larger energies than single bonds.

Enthalpy and Bond Changes

  • We can use bond energies to calculate the enthalpy change of a reaction.

 Formula for Bonds Energies

  • Where
    • D = bond energies.
    • n = number of moles (the coefficient in a balanced equation)
Example
  • Calculate the enthalpy change for the synthesis of hydrogen fluoride.

 

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