Gibbs Free Energy

Time for Gibbs Free Energy, the most important equation for understanding reaction favorability! It’s going to be important that we understand the significance of all the terms of this equation.  

1. Enthalpy (ΔH°) is the sum of bond dissociation energies for the reaction.

  • Negative values (-) indicate the making of new bonds = Exothermic
  • Positive values (+) indicate the breaking of new bonds = Endothermic


2. Entropy (ΔS) is the tendency of a system to take its most probable form.

  • Negative values (-) indicate less probable = Unfavored
  • Positive values (+) indicate more probable = Favored


3. Temperature (T) amplifies the effect of entropy on the overall favorability.

  • Some reactions require more than one step to go to completion. The ΔGo is the sum of all the steps


  • Transition states are high-energy species that CANNOT be isolated. They involve bonds being broken and made at the same time.


  • Intermediates are high-energy species that CAN be isolated. They rest at a higher energy state than normal.