How can I find the activation energy in potential energy diagrams?
The Activation Energy is the amount of energy needed to reach the "top of the hill" or Activated Complex. The Activated Complex is an unstable, intermediate product that is formed during the reaction. Once the reaction has obtained this amount of energy, it must continue on.
For example, the Activation Energy for the forward reaction
(A+B --> C + D) is 60 kJ and the Activation Energy for the reverse reaction (C + D --> A + B) is 80 kJ.