Collision Theory of Chemical Reactions: A detailed study

Do you ever ponder the mechanics of how things work? What must be in place for a response to occur? Are there any response guarantees even if all of the prerequisites are met? Collision theory is the solution to all of these problems. Let us take a look at what collision theory is and how it applies to various situations.

Collision theory of chemical kinetics

The study of chemical reaction kinetics and collision theory has achieved significant advances that are critical in today’s fast-paced environment. From everyday use products to the most sophisticated machinery, in some way or another all products have chemical reactions linked with them.

In 1916-1918, Max Trautz and William Lewis created the Collision Theory of Chemical Interactions based on the kinetic theory of gases to understand these chemical reactions better. We have studied the gas kinetic theory. 

Collision theory of chemical reactions

How reactions occur and why they occur at varying rates is explained by collision theory. It states that:

• When two molecules come into contact, they must respond.
• To cause a reaction, the molecules colliding must have enough energy to shatter the bonds between molecules.
• A rise in temperature increases the possibility of bond cleavages and rearrangements because molecules move faster and clash more violently.
• Reactions involving neutral molecules cannot proceed unless the activation energy required to stretch, bend or distort at least one bond has been gained first.

Activation energy

The energy that must be overcome for a reaction to occur is known as “activation energy.” This is the smallest amount of energy necessary to begin a chemical reaction.

Collision theory of chemical reactions in brief

Collision theory helps us understand why some chemical processes proceed faster or slower than others. The following is a basic bimolecular example:

If two molecules A and B are to react, they must be near enough to break some of their existing bonds and form new bonds necessary to generate products. This is called  collision. The greater the concentration of A and B in a gas, the more likely they will collide. Doubling A’s concentration will result in a twofold increase in A-B collision frequency. Doubling the concentration of B will yield the same result.

However, mere collision of molecules is insufficient. For the process to take place, they must be directed in a precise way. Molecules must come into contact with each other on the proper side for the collision to cause the subsequent response.

Collision hypothesis temperature dependency

At the molecular level, thermal energy acts like a compass. A higher temperature causes more collisions between the molecules for a bond to be broken, resulting in a greater possibility of bond cleavage. Thermal energy is the most common means of supplying activation energy.

The activation energy is returned in vibrational energy that is promptly released as heat when the reaction completes and products are created. When molecules come into contact, they must have energy levels larger than or equal to the activation energy.

The rate of reaction of a bimolecular elementary reaction, A + B Products, is,

ZAB= e -Ea/RT 

In this equation, ZAB denotes the collision frequency of reactants A and B, and e –Ea/RT indicates the proportion of molecules with energies equal to or higher than the reaction activation energy. Because of this, each reaction has a variable rate of response. The activation energy and frequency of the reactants in various reactions are variable.

An effective collision meets all of the collision theory’s requirements and results in a new product. Thus, the activation energy and the correct orientation of molecules are two of the most critical factors in collision theory.

Conclusion

In the collision theory of chemical reactions, the reactant molecules are modelled as hard spheres, and the reaction is predicted to occur when the spheres collide. In one unit volume of reacting mixture, collision frequency refers to the number of collisions occurring in a second. The pace of a chemical reaction may also be affected by activation energy. Chemical reactions need a source of energy for their reactions to take place.