In an exothermic reaction if H is the enthalpy then activation energy is:
For an endothermic reaction, energy of activation is Ea and enthalpy of reaction is ΔH (both of these in kJ/mol). Minimum value of Ea will be:
In an exothermic reaction A→B, the activation energy of reverse reaction is twice that of forward reaction. If enthalpy of the reaction is -80 kJ mol−1, the activation energy of the reverse reaction is :