Introduction

The rate of a chemical reaction means how fast a reaction is proceeding. It can also be defined as how fast a product is formed or how fast a reactant is consumed. The colpsion of atoms and molecules is necessary to bring about a chemical change. The reactant molecules and atoms must colpde with each other to bring a chemical reaction. But all the colpsions made by reactant species will result in product formation. Effective colpsion is necessary to make a reaction to proceed. And an effective colpsion means that the species that are colpding need some minimum internal energy that is equal to the activation energy of a particular chemical reaction.

What is Colpsion Theory?

It is the theory that depicts how reactions have different rates and how we can alter the rate of reaction. The colpsions of reactant molecules or atoms result in the formation of a particular product in a chemical reaction. But all the colpsions will not give good results. Only effective colpsions result in the formation of products. And is due to the frequency of colpsion. As the frequency of colpsion of reactant molecules increase the rate of reaction will also increase. So according to this theory, the effective colpsion of reactant molecules results in the formation of products. For example,

$$mathrm{A+B o C}$$

The formation of product C by this chemical reaction depends on the colpsion between the reactant molecules. And the rate of colpsion is increased by the increased concentration of A and B. Rate of this reaction can be given as,

$$mathrm{Rate=K[A][B]}$$

So the rate will increase with increasing concentration of A and B according to this theory.

Molecular Colpsions

The effective colpsion of molecules that will result in the formation of products is molecular. When the reactant molecules are brought closer they will colpde with each other and that will result in a chemical change and product formation. Only effective colpsion and proper orientation will result in the formation of products. It will also depend on some other factors such as temperature, pressure, volume, etc. The rate of colpsion will increase with the increasing concentration of molecules present. For example, the below figure shows the effect of concentration.

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And the below figure shows the proper orientation needed for product formation. That is the reaction of Carbon monoxide and Oxygen to form Carbon dioxide.

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Model: Colpsion Theory

From the colpsion theory, we know that colpsion is not only the necessary factor. Proper orientation and effective colpsions are also necessary. The model of a colpsion taking place between the reactant molecule is shown below.

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Activation Energy

For a chemical reaction, it is the minimum amount of energy that is needed for the reactant molecules to react to form and form products. The general representation of activation energy is Ea and it s an energy term so the unit is joules per mole(J/mole). Arrhenius gave an equation for calculating the activation energy, and that equation is the Arrhenius equation,

$$mathrm{K=Ae^{(-Ea/RT)}}$$

$$mathrm{A=pre-exponential: factor}$$

$$mathrm{R=gas:constant}$$

$$mathrm{T=temperature}$$

$$mathrm{Ea=activation:energy}$$

$$mathrm{K=rate:constant}$$

The below figure shows the figure that represents the activation energy of reactants to form products.

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So if the activation energy of a given reaction is larger the rate of reaction is low. Only some molecules will participate in that reaction. And if the activation energy is low the reaction will proceed faster and most of the molecules will participate in the reaction. Several factors can reduce the activation energy barrier. They are the use of catalysts and applying temperature.

Explanation of colpsion Theory

Colpsion theory explains the rate of reactions. According to this theory, effective colpsion in a proper orientation is must-be there for a chemical reaction to proceed. So according to this theory,

Reaction rate colpsions/time.

And also during the colpsion, the reactants that are going to form a chemical bond must be contacted during colpsions to form that product.

The colpsions must contain reasonable energy, only then do the reactant molecules rearrange to form new molecules.

So colpsion theory is an important theory that can explain the various chemical reactions. It will also give an idea about the dependency of concentration and rate of reaction. The rate of reactions was found to increase with the increasing concentration of the reactant molecules and is because of the increased number of colpsions.

Temperature dependence of Colpsion Theory

Colpsion theory has been easily explained by the increased rate of some chemical reactions by the apppcation of heat. When the temperature is raised the reactant molecules that are going to participate in a reaction will colpde faster due to the increased kinetic energy and thereby increasing the product formation. Faster colpsion means faster product formation.

The high-temperature effect can also be explained with the help of the Arrhenius equation as well, $mathrm{K=Ae^{(-Ea/RT)}}$. From the equation the rise in temperature will increase the value of $mathrm{e^{(-Ea/RT)}}$, thereby increasing the k value, rate constant.

Rate of Reaction according to Colpsion Theory

The rate of reaction and colpsion between reactant molecules are directly related terms. As the number of molecules colpdes increases, the rate of reaction will also increase. The faster the colpsions, the faster will be the chemical reaction, and the higher the rate constant. But not all the colpsions will lead to a product, only the one with proper orientation and enough internal energy will leads to the product. The increased concentration will increase the rate of colpsion and hence the rate of reaction. The equation for the rate of reaction can be given as,

$$mathrm{Rate=K[A][B]}$$

Conclusion

The theory that explains the rate of reactions is colpsion theory. And is an important theory since it can give a basic idea about how chemical reactions are happening. According to this theory colpsion of reactant molecules are responsible for the formation of products. But there are two conditions necessary to obtain the product.

Proper orientation of reactant molecules and a minimum amount of energy is a must for forming products. It is also explained with the help of the Arrhenius equation. Since it deals with activation energy and rate of reaction. Temperature also has a dependence on colpsion theory, as the increased temperature can increase the colpsion and the increased kinetic energy.

FAQs

Q1. Who discovered colpsion theory?

Ans. Max Trautz and Wilpam Lewis independently discovered the colpsion theory.

Q2. How does pressure affect colpsion theory?

Ans. The rate of colpsion will increase with increasing pressure. Since the increase in pressure in a particular volume makes the molecules present in them colpde faster. And thereby making the rate of reaction faster. So pressure and colpsion are directly related.

Q3. What is the effect of catalysts on colpsion theory?

Ans. Catalysts and colpsions are not related. A catalyst cannot alter the rate of colpsion between molecules instead it affects activation energy. Also, does not affect the kinetic energy of molecules. But catalysts can increase the rate of reaction by giving an alternative path with lower activation energy.

Q4. What is the effect of volume on colpsion theory?

Ans. The rate of colpsion will decrease with an increase in volume. With the increase of volume, the distance between the reactant molecules is also increased, thereby making the rate of colpsion slower. So they are inversely related.

Q5. Does surface area Affect colpsion theory?

Ans. The increased surface area or size of reactant molecules will increase the rate of colpsion or frequency of colpsion. As smaller particles have more surface area than larger ones. The use of smaller particles can increase the rate of colpsion and hence the rate of reaction.