Chemical reactions can proceed at different rates. Some of them finish within a few seconds, others can drag on for hours, days, or even decades. In order to determine the productivity and size of the necessary equipment, as well as the amount of product produced, it is important to know the rate at which chemical reactions proceed. It can have various sizes, depending on:
-concentration of reacting substances;
-Temperature system.
At the end of the nineteenth century, the Swedish scientist S. Arrhenius derived an equation showing the dependence of the rate of a chemical reaction on an indicator such as activation energy. This indicator is a constant value and is determined by the nature of the chemical interaction of substances.
According to the scientist, only those molecules that are formed from ordinary and are in motion can react with each other. Such particles were called active. Activation energy is the force that is needed for the transition of ordinary molecules to a state in which their movement and reaction become the fastest.
In the process of chemical interactions, some particles of the substance are destroyed, while others arise. In this connection changes between them, that is, the electron density is redistributed. The rate of a chemical reaction at which the old interactions would be completely destroyed would have a very low value. The amount of energy reported must be high. Scientific studies have shown that during the interaction of substances, any system forms an activated complex, which is its transitional state. At the same time, old ties are weakening, and new ones are only emerging. This period is very small. It is a split second. The result of the collapse of this complex is the formation of starting materials, or products of chemical interaction.
In order for the transition component to arise, it is necessary to give activity to the system. For this, the activation energy of a chemical reaction is needed. The formation of the transition complex is determined by the strength that the molecules possess. The amount of such particles in the system depends on the temperature regime. If it is high enough, then the proportion of active molecules is high. In this case, the magnitude of the force of their interaction is higher than or equal to the indicator called “activation energy”. Thus, at sufficiently high temperatures, the number of molecules capable of forming a transition complex is high. As a result, the rate of a chemical reaction increases. On the contrary, if the activation energy is of great importance, then the fraction of particles capable of interaction is small.
The presence of a high energy barrier is an obstacle to chemical reactions at low temperatures, although their probability exists. Exothermic and endothermic interactions have different characteristics. The first of them proceed with the least activation energy, and the second with the highest.
This concept is also used in physics. The activation energy of the semiconductor is the minimum force that should give acceleration to the electrons to go into the conduction band. During this process, bonds between atoms are broken. In addition, the electron must move from the valence band to the conduction sector. An increase in temperature is the cause of increased thermal displacement of particles. In this case, part of the electrons goes into the state of free charge carriers. Intercoms can also be broken by an electric field, light, etc. The activation energy is much larger for intrinsic semiconductors compared to impurity ones.