Bond Enthalpy

• What happens in a reaction?

  Bonds are made and broken
• Why is breaking bonds endothermic?

  Need energy to break bonds

  AH+
• What happens when bonds are formed?

  Energy is released so it's exothermic

  AH-
• What is the enthalpy change for a reaction

  Overall effect of the bonds making and breaking

  If more energy to break bonds are needed than is released when bonds are made =AH+

  If less AH-