Example of Exothermic Reactions

Thermochemistry is the part of chemistry that is responsible for the study of the relationship between chemical reactions and changes in temperature during reactions. When two substances react, the reaction can be endothermic or exothermic.

Endothermic reactions are those that absorb heat.

Exothermic reactions are those in which while two or more substances are reacting, they release energy in the form of heat. Once the reaction is finished, the resulting product is called an endothermic body, because when to decompose it, it is necessary to provide it with heat.

The main characteristics of endothermic reactions are as follows:

• The reaction only requires a catalyst or trigger, sometimes it can also be spontaneous.
• Once the reaction starts, it is diffused in a chain by the reactive substances and does not stop until the components have fully reacted to each other, without the need for power external.
• The resulting substances (endothermic bodies) are chemically stable compounds, so they do not decompose easily.
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• To decompose endothermic bodies, it is necessary to provide them with heat for decomposition to take place.
• When the decomposition reaction begins, it constantly requires heat to be supplied to it, because by interrupting the supply, decomposition is interrupted.

Examples of exothermic reactions

One of the exothermic reactions that has been tried to take advantage of is the formation of water. Hydrogen (H₂) is a gaseous element that, when exposed to air, catches fire. This happens because it combines with oxygen (O₂), producing an exogenous reaction, that is, hydrogen reacts spontaneously with oxygen, producing water and giving off heat:

2H₂ + O₂ -> 2 H₂O + heat

This characteristic of the formation of water has been used to create hydrogen engines, where the reaction of formation of water and the energy it gives off is used to move the pistons of an engine, having as a residue only Water. The drawback of these systems is that in the event of a crash or leak, due to the flammability of hydrogen, there is a very high risk of fire or explosion.

Another example of an exothermic reaction is termite. Termite is a mixture of very fine aluminum powder and some metallic oxide, such as copper oxide or iron oxide. For the reaction to begin, ignition is necessary, usually with a magnesium strip. This provides the initial energy that is propagated in a chain throughout the mixture until the components react completely. In the reaction, the Aluminum combines with the oxygen of the oxide with which it is mixed, forming aluminum oxide and releasing the other metal.

Faith₂OR₃ + 2Al -> 2Al₂OR₃ + 2Fe + heat

The reaction is very violent and gives off a lot of heat. This causes the metal from which the oxygen is released (in the example, iron) to melt. This feature is used in the rail industry to weld rails once they have been placed or changed.