Activation energy

Activation Energy

  • Activation energy is the minimum energy required by reactant molecules to successfully react to form product(s).

  • Activation energy can also be defined as the energy barrier that must be overcome for a chemical reaction to occur.

  • It helps to think of activation energy as a hill. For a reaction to happen, the reactants need enough energy to get over the hill.

  • The magnitude of activation energy can also give an indication about how fast a reaction may proceed. Reactions with low activation energies tend to be faster than reactions with high activation energies.

  • Activation energy affects both the forward and reverse reaction rates. Therefore, it is a key component in determining the equilibrium position of a reaction.

  • Increasing the temperature of a reaction system may provide particles with enough energy to overcome the activation energy barrier, thereby increasing the rate of reaction.

Effect of Catalysts on Activation Energy

  • Catalysts are substances that can lower the activation energy of a chemical reaction, thereby speeding up the reaction rate, but remain unchanged at the end of the reaction.

  • They do so by providing an alternative reaction pathway with a lower activation energy barrier.

  • By lowering the activation energy, more molecules will have sufficient energy to react, increasing the frequency of successful collisions and thereby increasing the rate of reaction.

  • Catalysts do not change the energetics of the reaction, meaning they do not affect the overall enthalpy change (∆H) of the reaction.

  • An enzyme is a biological catalyst that lowers the activation energy for reactions in living organisms.

Application of Activation Energy

  • Activation energy concept is used in various areas such as pharmaceuticals in predicting shelf life of drugs, fuel cells in optimising reaction rates and in the food industry in analysing reaction rates during cooking or spoilage of items.

  • Understanding the concept of activation energy is also important in thermodynamic predictions and the development of energy-efficient processes in the chemical industry.