The reaction of exchange, substitution, compound, decomposition are considered in the course of the school curriculum. We analyze the features of each type, give examples of interactions.
Definition of the term
What is the reaction of the compound, examples of which are considered in educational institutions at the first stage of training? To begin with, we note that the term "chemical reaction" in chemistry is considered the second most important.
In our world, a reaction of a compound takes place every minute, the equations of which are familiar to us, but we don’t even think about them.
For example, obtaining carbonated drinks, burning firewood are typical examples of compound reactions.
This process involves obtaining products with a certain qualitative and quantitative composition from the starting chemicals.
Signs of a chemical reaction
Any process, including the chemical reaction of a compound, is accompanied by certain signs:
- light or heat emission;
- discoloration of the solution;
- the release of a gaseous substance;
- the appearance of a specific smell;
- dissolution or precipitation.
Reaction conditions
Depending on the characteristics of the qualitative and quantitative composition, the chemical reaction of the compound can proceed under different conditions.
For example, an interaction of the form 2 + 2 = 2 (lime slaking) proceeds without preliminary heating, accompanied by the release of a significant amount of thermal energy.
How is the reaction of the compound prepared? The equations of such processes suggest writing on the left side of the starting materials, and on the right side the reaction product is compiled.
4Na + O 2 = 2Na 2 O
Similar processes are inherent in organic substances. So, a qualitative reaction to unsaturation (the presence of a multiple bond) is the oxidation reaction of the starting material with potassium permanganate.
Wood burning
This process proceeds according to the equation:
C + O 2 = CO 2
This is a typical reaction of a compound, examples of which have already been given above. What is the essence of this process? In the interaction of firewood with oxygen contained in the air, the formation of carbon dioxide molecules. The process is accompanied by the formation of a new molecule of a complex bond compound, is an exothermic reaction.
Is a compound reaction possible between complex substances ? Examples of interactions with simple substances were considered above, but this type is also characteristic of complex substances. A typical variant of such an interaction can be considered the reaction of slaking lime.
CaO + H 2 O = Ca (OH) 2
This process is also accompanied by the release of a significant amount of thermal energy. Among the specific features of this process, we note its spontaneity.
Classification
According to the composition of the starting materials and reaction products, the reaction of the compound, decomposition, substitution, exchange is distinguished. Consider their examples, as well as provide definitions of such processes.
Substitution is the replacement by atoms of a simple substance of a part of a complex compound.
Joining is the process of combining several simple or complex substances into one more complex one. Examples of such processes can be given from inorganic and organic chemistry.
2H 2 + O2 = 2H 2 O
This process occurs with the release of a significant amount of heat, so an explosion is possible.
C 2 H 4 + H 2 = C 2 H 6
When hydrogen is passed through ethylene, a double bond breaks, and a saturated (saturated) hydrocarbon is formed.
Decomposition is those chemical reactions, as a result of which several substances are formed from one complex compound having a simpler qualitative and quantitative composition.
Ion exchange reactions a are processes occurring between complex substances, as a result of which the exchange of constituents occurs.
There are three conditions for the occurrence of such a process: gas evolution, precipitation, and the formation of a slightly dissociable substance.
This interaction is called esterification, since the final product of the interaction is an ester. A prerequisite for the process to proceed is the introduction of concentrated sulfuric acid into the reaction mixture.
Division by the state of aggregation of interacting substances
All chemical processes are classified according to this attribute into homogeneous and heterogeneous interactions. In the first case, the starting materials and reaction products are in the same aggregate state, and a different state is allowed for heterogeneous species.
For example, the following interaction will be a homogeneous process:
H 2 (gas) + Cl 2 (gas) = ​​2HCl (gas)
As a heterogeneous reaction, you can consider the following option:
CaO (tv) + H 2 O (W) = Ca (OH) 2 (pp)
By change in oxidation state
The reaction of the compound, the formula of which was given above (the formation of water from simple substances), is a redox process. The essence of the process is that the acceptance and return of electrons occurs.
Among the reactions of the compound, there are also such processes that are not accompanied by a change in the oxidation state, that is, they are not OVR:
CaO + H 2 O = Ca (OH) 2
By the nature of the course
Depending on whether the process can proceed only in the forward direction or whether the reaction also occurs in the opposite direction, irreversible and reversible interactions are distinguished in chemistry.
For example, a qualitative reaction to organic compounds is irreversible, as it leads to the formation of an insoluble or gaseous substance. An example of such a qualitative interaction is the reaction of the “silver mirror”, which is a qualitative way of determining aldehydes in a mixture.
Among the typical variants of reversible reactions that are capable of proceeding in two mutually opposite directions, we note the esterification reaction:
CO 2 + H 2 O = H 2 CO 3
On the use of catalyst
In some cases, it is necessary to use an accelerator (catalyst) in order for the chemical process to start. An example of catalytic interaction is the decomposition of hydrogen peroxide.
Features parsing OVR
Among the issues that most often cause difficulties for students, is the arrangement of the coefficients in the reaction using the electronic balance method. To begin with, there are certain rules according to which the degree of oxidation of individual elements can be determined in each substance.
Regardless of whether a simple or complex substance will be considered, their sum should be equal to zero.
The next step will be the selection of those substances or individual chemical elements for which the oxidation state has changed. They are written out separately, showing the signs “plus” or “minus” the number of received or given electrons.
Between these digits find the smallest number, dividing by which the number of received and given electrons will result in integers.
The resulting numbers are stereochemical coefficients placed in the equation of the proposed process. An important step in the analysis of redox reactions is the determination of the oxidizing agent and reducing agent, as well as the recording of ongoing processes. As the reducing agent, those atoms or ions are selected which, during the course of the interaction, increased their oxidation state; on the contrary, this indicator is characterized by a decrease in this index.
Does organic chemistry involve any changes in this algorithm? The reaction of the compound, substitution, decomposition, proceeding with a change in the oxidation state, is considered by a similar algorithm.
There are certain features in the arrangement of oxidation states in organic compounds, but their sum should also be equal to zero.
Depending on how the oxidation state changes, several types of chemical interactions are distinguished:
- disproportionation - is associated with a change in the oxidation state of the same element up and down;
- counterproportionation - involves the interaction of a reducing agent and an oxidizing agent, in the composition of which one and the same element, but in different degrees of oxidation.
Conclusion
As a small result, we note that when substances interact with each other, their changes and transformations occur. Chemical reactions are the transformations of one or more reagents into products having a different qualitative and quantitative composition.
If in nuclear transformations a change in the composition of the nuclei of atoms is observed, then in the case of chemical reactions this is not the case, only the redistribution of nuclei and electrons occurs, leading to the appearance of new compounds.
The processes that occur can be accompanied by the release of light, heat, the appearance of odors, precipitation, and the formation of gaseous substances.
There are many options for classifying organic and inorganic interactions according to various criteria. Among the most common options, mention can be made of changes in oxidation states, state of aggregation, reversibility of the course, mechanism of the process, and the use of a catalyst (inhibitor).
Chemical reactions are the basis not only of industrial production, but also the basis of life. Without metabolic processes that take place in living organisms, existence would be impossible.