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Kick Starting Chemical Reactions by Simplifying the Concept of Activation Energy

by Mar 30, 2018Homework and Assignment Support

Activation energy is an important part of a chemical reaction and holds prime importance in determining a curve for any reaction.
Let us try to understand the meaning of activation energy with an example!
Assuming a ball try to roll up a hill and gaining enough energy into the system the ball will further roll down. Thee certain amount of energy the ball had at the beginning is known as the potential energy. To reach the potential energy the ball has to put a certain energy that is known as activation energy.
Hence, activation energy is a very essential criterion to take place during any chemical reaction.
What happens when a system do not have activation energy?
If a system does not have enough activation energy then it will go back to where it was before.
Hence, simply putting the meaning affront, one can say that activation energy is how much energy one has to put into a system to have a chemical reaction occur.
It also depends upon the collisions between molecules; mostly they are unsuccessful collisions as they do not contain enough energy. The reason however due to the lack of proper orientation.
In rare cases, the collisions can also be successful, and then it is possible for a chemical reaction to occur.
Let us understand the bits more appropriately, with a question,

  1. Q) In a unimolecular reaction the following reaction has activation energy of 262 kj/mol.

C4H8 (g) à 2C2H4 (g)

At 600.0 K the rate constant is 6.1*10^-8s^-1. What is the value of the rate constant at 750.0 K?
Probable solution of the above equation can be calculated as follows,
It has to be calculated according to the Arrhenius’  law and its formula for  the  rate  constant that is  dependent  on  the  activation  energy  and temperature.
After that one needs to find the rate constants ratio at different temperature.
Ultimately, the answer of the following reaction has activation energy of 262 kj/mol is 2.2 x 10-3 s-1.
The case of a unimolecular reaction is special as here is mostly going to be interactions between the molecules and solvent or background molecules.
One the other hand in the case of bimolecular or trimolecular reaction it is going to be with other molecules.
However, in either case, it is going to be based on Maxwell-Boltzmann distribution.
Activation energy is a crucial component in a reaction as it can widely affect the rate of a reaction.
The first things that make a reaction to occur, or simply put in order to react molecules must,

  • Collide
  • Contain sufficient energy
  • At right angle or geometry

The energy a system needs to gather in order to take part in a reaction is called as activation energy and its symbol is Ea.
As change in activation energy is a factor affecting the reaction rate, other than

  • Rate of collision between molecules
  • Percentage of collision with direction of a reaction
  • Percentage of collision with required energy

Hence activation energy is a necessary topic under the unit off chemical reaction that is the driving force of a reaction.