Through chemical kinetics, information is obtained about the reaction rate and what factors influence it.
Chemical kinetics is the name of a specialty within the field of physical chemistry that focuses on the study of reaction speed . Its purpose is to establish, experimentally, how quickly a given chemical reaction occurs and how the effect of temperature and issues linked to a catalyst , the reaction mechanism and concentration , for example, influence it.
It is interesting to know that, depending on the number of steps covered, a distinction is made between an elementary reaction (it includes a single transition state and has a simple reaction rate ) and a complex or compound reaction (it involves various stages). Likewise, it is possible to differentiate between homogeneous kinetics (developed in one phase) and heterogeneous kinetics (with more than one phase and dependent on the area of a certain surface).
Basic concepts of chemical kinetics
Below we will describe basic concepts of chemical kinetics in order to facilitate understanding of the characteristics and application of this area of scientific research.
First of all, the idea of reaction speed becomes visible, which marks the amount of a substance that, in a certain reaction and in a unit of time , manages to transform. There are multiple factors (such as the nature of each reaction and the effect of pressure ) that determine this speed . In connection with it, the rate equation achieves notoriety, an expression that identifies a mathematical formula that serves in the field of chemical kinetics to establish a relationship between the reaction rate and the concentration of each of the reactants . These structures contain the rate constant , a coefficient that increases when the temperature rises. If it is an exothermic reaction and the temperature increases, a decrease in the equilibrium constant is noted; In an endothermic reaction , this constant increases.
To check how much and how the rate constant varies in a chemical reaction as a function of temperature , to add more precision, we must apply the so-called Arrhenius equation . This formula, named after the Swedish professor and scientist Svante August Arrhenius, pointed out that, in order for a reactant to be transformed into a product , in principle it must reach a basic amount of energy (considered activation energy ).
It is also necessary to master the concept of reaction order that is calculated with respect to a particular reactant to find out the power to which, in the rate law , the concentration of the analyzed material has been raised.
Water, whose chemical formula is H2O, is a substance capable of reacting with acidic oxides and can react with basic oxides, for example.
Variables that affect the reaction speed
The catalysts , the contact surface , temperature , pressure and concentration are variables that affect the reaction rate .
The first of the factors listed is a substance capable of altering the rate of a certain chemical reaction . If they accelerate it, then it is described as a positive catalyst ; If they cause a slowdown, it is a negative catalyst .
When analyzing the surface reaction within the framework of heterogeneous catalysis , it is possible to verify that, as the area corresponding to the contact surface increases, an increase in the reaction rate is recorded.
Due to the effect of temperature, the reaction speed is also modified since, the more thermal exposure, the greater the kinetic energy evident in the molecules.
The elevated pressure generates changes in the reaction rate if the phase is condensed and causes it to accelerate significantly in a gaseous reaction .
The reaction rate also experiences variations due to the effect of concentration , as explained in the collision theory and noted in the rate law . In this context it can be observed that, as the concentration of reactants increases, the collision frequency increases.
Chemical kinetics is applied in the pharmaceutical industry and is useful for analyzing the decomposition process of food substances, for example.
Fields of application of chemical kinetics
The fields of application of chemical kinetics are varied, but they are always areas in which some chemical reaction comes into play.
This is what happens in the development of more than one chemical compound from a synthesis reaction . It is possible to recognize pharmaceutical chemical kinetics that allows us to analyze how a drug is useful for the human body and how it absorbs, distributes, metabolizes and eliminates the product.
The connection between chemical kinetics and the environment , food production, medicine and biology should not be overlooked either. Experts in petrochemistry , for their part, take advantage of the knowledge and resources from chemical kinetics in order to examine the procedures through which changes in the concentration of one or more chemical reagents are detected.
By deepening knowledge regarding these last issues, one learns, for example, that by paying attention to chemical kinetics , it is possible to study the process (the speed ) that leads to the decomposition reaction, the deterioration, of a food.