Activation Energy

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What is activation energy?

[Srothery 2k]

Activation energy, Ea, is the amount of energy required to be overcome before any reaction can take place, regardless of whether the reaction is net endo- or exo- thermic. On a potential energy diagram, it can be determined by measuring the energy difference between: a) the reactants and the top of the curve if the reaction is exothermic or b) the products and the top of the curve if the reaction is endothermic.

[Vivian Kim 3F]

Just to add on, when a catalyst is added, the activation energy is lower, which is what causes the reaction to become faster. This is because the reactants now overcome less energy to form the products.

[Ananya Ravikumar 1I]

Activation energy is the energy required for the reactants to be converted into their transition states, and they react in these states. Transition states are therefore high-energy states. In the transition state, it becomes possible for the reactant's bonds to break and for new bonds to form. Gaining this energy takes time, and a catalyst speeds up a reaction by decreasing the activation energy/the energy to be gained before the reaction can start. Therefore, it speeds up the reaction. As mentioned above, all types of reactions (be it endothermic or exothermic) need this activation energy to get started. The endothermic or exothermic nature of the reaction is determined by the difference in the final energy levels of the reactants and products.

[Jeilyn Rhee 1J]

- Activation energy(Ea) is the minimum energy required for the reaction to proceed. It is also visually seen as the height of the activation barrier in the graph. To easily describe it, the little "hump" in the reaction graph is the value of the activation energy.
- The activation energy "hump" get lower if the reaction is working with catalyst. As a function of catalyst, it lowers the activation energy. Regardless whether it's forward or reverse equation, the activation energy is lowered for both reactions with catalyst.
- The activation energy of forward rxn and reverse rxn and delta H value is related through the equation: delta H = Ea (forward) - Ea (reverse)
- If the activation energy is greater at forward rxn than reverse rxn, which means that the reaction is endothermic. That being said, if the activation energy is great at reverse rxn then forward rxn, it means that the reaction is exothermic.
- Temperature is also related to activation energy. If the temperature increases, the rate constant (k) with greater activation energy between forward and reverse equation.
- Activation energy can be calculated through the Arrhenius equation:
k/A=e^(-Ea/RT)
ln(k/A)=-Ea/RT
Ea=-RTln(k/A)

[Neha Humbe 3E]

Hi, activation energy is the minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction. Activation energy on a graph can be is between the reactants and the transition state, which can be seen in the image below. Hope this helps!