Activation Energy (DP IB Chemistry): Revision Note
Activation energy
What is activation energy?
For a reaction to take place, the reactant particles need to overcome a minimum amount of energy
This energy is called the activation energy (Ea)
In exothermic reactions, the reactants are higher in energy than the products
In endothermic reactions, the reactants are lower in energy than the products
Energy profile of an exothermic reaction, showing Ea
Energy profile of an endothermic reaction, showing Ea
Even if particles collide with the correct orientation, the reaction will not occur unless they have at least the minimum energy required, the activation energy (Eₐ)
For a collision to be successful, particles must both:
Collide in the correct orientation and
Have energy equal to or greater than the activation energy (Eₐ) of the reaction
Examiner Tips and Tricks
How to find the activation energy of a reverse reaction
You may be required to show or calculate the activation energy for a reverse reaction using a labelled energy profile like those above
The activation energy for the reverse reaction is found by:
For an exothermic reaction = ∆H + Ea (forward)
For an endothermic reaction = Ea (forward) - ∆H
Calculations of the value of the activation energy from experimental data are not required at Standard Level but are required in Higher Level Chemistry
For more information on how to calculate activation energy, see our revision notes on Determining Activation Energy & the Arrhenius Factor
You've read 0 of your 5 free revision notes this week
Unlock more, it's free!
Did this page help you?
