Question

How does the collision theory explain how chemical reactions occur?

Answer 1

To explain the chemical reaction happening in terms of collision theory, the basic idea of collision theory should be known. The terms like activation energy, threshold energy have a major role in explaining the chemical reactions with the aid of collision theory.

Complete answer:
So in the question we are asked to explain about the chemical reaction happening in terms of collision theory, so we should have some basic idea about the theory and the conditions of the theory to predict the final product.
So collision theory was suggested by Arrhenius and Van't Hoff. According to this theory a chemical reaction is carried by the mutual collision of reactant molecules. But not all the collisions will result in chemical reactions. Only those molecules which have the threshold energy will collide with each other and result in chemical reaction and forms form the final product.
For better understanding let us consider an example, the combustion reaction of carbon and oxygen. The number of collisions per second is ${{10}^{9}}$.The reaction rate is medium even though the number of collisions is very high. This reveals that all the collisions in between the molecules will not lead to a chemical reaction. The collisions of molecules with a minimum energy leads to a chemical reaction. The minimum energy content required by the molecule to take part in the chemical reaction is called the threshold energy. And the collisions made by the molecules with threshold energy are considered as the effective collisions which will lead to the product formation. The number of effective collisions taking place in unit volume in unit time is referred to as the collision frequency.

Note:
When the temperature is increased the more molecules will acquire the threshold energy and hence the number of effective collisions per second increases and the rate of reaction also increases.
A catalyst also can be used to increase the rate of reaction, as it reduces the energy required for carrying out an effective collision.
As per collision theory, in order to carry a reaction the following conditions are essential:
-threshold energy by the molecules
-Molecules should be in proper orientation.