Chemistry of Chemical Kinetics


Chemical kinetics is the study of chemical processes in terms of reaction rate, intermediate production, atom rearrangement, and the influence of various factors. A number of factors influence the rate of reaction—they are the catalyst, the reactant concentration, and the temperature. Since it is impossible to forecast the reaction rate, it must be determined empirically.

The word kinetics mainly refers to the rate of change of a quantity. The rate of change of displacement, for example, is expressed as velocity. The rate at which velocity varies is called acceleration. This article will discuss the order and molecularity of reaction, the rate constant, and factors affecting the reaction rate.

Rate of Reaction

The rate of a chemical reaction is determined by the reactant or product concentrations, as well as the time needed to accomplish the chemical change. The change in concentration of a reactant or product in unit time may be described as the rate of a chemical reaction.

Factors Affecting the Reaction Rate

Certain variables, such as increasing the percentage of molecules with more extensive energies than the activation energy Ea, impact the reaction rate. The following are some of the elements that influence the rate of a reaction:

  • Concentration of reactants
  • Nature of the reactants
  • The physical state of reactants
  • The surface area of reactants
  • Temperature
  • Catalyst
Concentration of reactants

According to collision theory, reactant molecules collide with each other to generate products. The number of colliding particles increases as the concentration of reactants increases, resulting in an increase in the rate of reaction. For the majority of reactions, the concentration and rate of reaction are proportional. As a result, when the concentration is twice, the response rate is likewise doubled.

Nature of the reactants

The rate of reaction is also influenced by the sorts of chemicals involved. Acid/base reactions, salt production, and ion exchange are all examples of rapid reactions. The process that occurs during the development of a covalent bond between molecules that leads to the synthesis of bigger molecules is generally slower. Furthermore, the type and strength of bonds in reactant molecules have a significant impact on how quickly they turn into products.

Physical state of a reactant

The rate of change is highly influenced by the physical condition of a reactant, whether it is solid, liquid, or gas. To elaborate, if the reactants are in the same phase, such as in an aqueous solution, the thermal motion will bring them together. The reaction will be restricted to the interface between the reactants if they are in different stages. The reaction happens mostly at their point of contact, in the case of a liquid and a gas, at the liquid’s surface.


The number of collisions between reactant molecules per second increases as the temperature rises (frequency of collision). As a result, the rate of the reaction accelerates. However, temperature increases the rate of forward or backward reactions, depending on whether the process is endothermic or exothermic.


Catalysts change the reaction mechanism, which changes the rate of the reaction. Promoters and poisons are two types of catalysts that boost and reduce the rate of reactions, respectively. Some catalysts, such as enzymes, which are found in our bodies, boost the rate of various sorts of reactions, whilst others, such as catalysts, are specialised for only one type of reaction or a single type of reactant molecule. As a result, a catalyst boosts a chemical’s reaction rate.

Order and Molecularity

Order and molecularity of reaction are two terms used regarding the rate of reactions. The molecularity of a reaction refers to the number of reacting species (atoms, ions, or molecules) involved in an elementary reaction that must collide concurrently to produce a chemical reaction. A reaction’s molecularity is a whole number other than zero. It has a range of 1 to 3 values. By examining the reaction mechanism, it may be determined.

The sum of powers to which the reactant concentrations are increased in the rate law equation is known as the order of reaction. Experimentation determines it. Although, if we have the empirically established rate law expression, we may use rate law to predict the order of reaction. The number of steps in a reaction might be an integer or a fraction.


The study of chemical processes and reaction rates is known as chemical kinetics. This involves determining the factors that influence a chemical reaction’s pace, comprehending reaction processes and transition states, and developing mathematical models to predict and characterise a chemical reaction.