Collision theory states that for a chemical reaction to occur, the reacting particles must collide with sufficient energy. This means that the particles must possess enough kinetic energy to overcome the energy barrier that exists between the reactants and products.
The activation energy is the minimum amount of energy that the colliding particles must have in order to react. The rate of a chemical reaction is determined by the number of successful collisions that take place.
The higher the activation energy, the slower the rate of reaction. This is because there will be fewer particles that possess the required energy to react. So, the rate of a chemical reaction is determined by the number of successful collisions.
For example, let’s look at the reaction between chlorine and nitrosyl chloride.
In this first example, the collision between the two particles is unsuccessful. This is because the particles did not collide with enough energy to overcome the activation energy barrier. As a result, the particles bounce off each other and no product forms.
In contrast, the second example shows a successful collision, where the collision energy was equal to or greater than the activation energy. Therefore, the reaction takes place, and products form.
By manipulating factors that influence successful collisions, scientists can control the rate and efficiency of chemical reactions.