Bond Energies

• Bond energy

  The amount of energy needed to break one mole of a particular covalent bond
• Breaking bonds is an endothermic process as it requires energy from the surroundings
• Bond formation is an exothermic process as it releases energy to the surroundings
• Reaction of hydrogen and chlorine

  1. Break hydrogen-hydrogen bond and chlorine-chlorine bond (endothermic)

  2. Form two hydrogen-chlorine bonds (exothermic)
• Determining if overall reaction is exothermic or endothermic

  Compare total energy required to break bonds vs total energy released when bonds form. If negative it is exothermic if positive it is endothermic
• Reaction of nitrogen and hydrogen

  1. Break 1 nitrogen-nitrogen triple bond and 3 hydrogen-hydrogen bonds (endothermic)

  2. Form 6 nitrogen-hydrogen bonds (exothermic)