We explain what endothermic reactions are and some examples of them. Also, what are exothermic reactions.
What are endothermic reactions?
Endothermic reactions are chemical reactions they need the supply of caloric energy for them to occur. In order for the reactants to become products, these reactions absorb heat, which makes products obtained are left with higher energy levels than the initial reagents.
The enthalpy is a quantity that defines the flow of thermal energy in the chemical processes that occur at Pressure constant. Furthermore, this magnitude represents the exchange of Energy between a thermodynamic system and its environment. The variation of this magnitude (ΔH) in a chemical reaction is used to classify the reaction as endothermic or exothermic.
ΔH> 0 endothermic reaction.
ΔH <0 exothermic reaction.
These reactions are in common use in industry from chemical ice and cooling, as they can be generated in controlled environments to remove heat from the environments or others substances. Some of its applications were replaced with the cold generated by the cooling equipment.
Examples of endothermic reactions
Some examples of endothermic reactions are:
- Ozone production in atmosphere. This reaction is driven by ultraviolet radiation from the Sun, the molecules of oxygen (O2) are converted into ozone (O3), absorbing energy from said radiation in the process.
- The electrolysis of water. To separate the hydrogen (H) and oxygen (O) that make up water (H2O) it is necessary to add electric power in a procedure known as electrolysis, in which both types of atoms respond to the poles generated by the electric current added, it breaks your Chemical bond and it consumes energy.
- The photosynthesis. The process of nutrition of the plants occurs through a series of chemical reactions that break down the carbon dioxide (CO2) in the presence of water and sunlight. This series of reactions needs to consume energy to occur.
- Obtaining iron (II) sulfide. This compound is obtained in a laboratory after reacting iron and sulfur. For this reaction to occur it is necessary to supply heat energy using a burner (or a boiler if it is industrial conditions).
Exothermic reactions
An exothermic reaction is one that when it occurs releases energy in the form of heat or light To the environment. When this type of reaction occurs, the products obtained have lower energy than the initial reactants. The enthalpy change for this type of reaction is less than zero (ΔH <0).
Examples of this type of reaction are all forms of combustion and of oxidation, as is the case with gasoline or fossil fuels, which when burned in the presence of oxygen release an amount of energy much higher than that initially introduced (the engine spark). The same happens in the phase changes of the matter of the state gaseous to the liquid, or from liquid to solid.