Chemical reaction. Also known as a chemical change . Chemical process in which two or more substances called reactants, by effect of an energy factor, are transformed into other substances called products. Those substances can be elements or compounds.
Summary
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- 1 Chemical Reaction
- 2 Reactants and products
- 3 Characteristics of chemical reactions
- 4 Importance of chemical reactions
- 5 Steps Needed to Write a Lean Chemical Reaction
- 6 Classes or types of chemical reactions
- 7 Source
Chemical reaction
A chemical reaction is stated to be a process in which a substance (or substances) disappears to form one or more new substances. The chemical equations are mode represent chemical reactions.
Reactants and products
To understand and analyze them, chemical reactions are represented by chemical equations . Reactants are substances that when combined with each other through a process called chemical reaction form other different substances known as products of the reaction.
Characteristics of chemical reactions
- The new substances that are formed usually have a completely different appearance from the starting substances.
- During the reaction energy is released or absorbed: Exothermic reaction: energy is released in the course of the reaction and Endothermic reaction : energy is absorbed during the course of the reaction.
- The law of conservation of massis fulfilled : the sum of the masses of the reactants is equal to the sum of the masses of the products. This is so because during the reaction the atoms neither appear nor disappear, they only rearrange themselves in a different arrangement.
Importance of chemical reactions
The importance of chemical reactions is notorious in many aspects of daily life in phenomena such as explosions; vital processes such as feeding , breathing etc. All the substances that we use every day are or were the product of chemical reactions.
We are surrounded by chemical reactions; They take place in laboratories, but also in factories, automobiles, thermal power plants, kitchens, the atmosphere , the interior of the Earth … Even in the human body, thousands of chemical reactions occur at every moment, which determine what we do and think.
Steps that are necessary to write an adjusted chemical reaction
- What are the reagents and products.
- An unadjusted equation is written using the formulas of the reagents and the products.
- The reaction is adjusted by determining the coefficients that give us equal numbers of each type of atomon each side of the reaction arrow, generally integers.
Example: Consider the combustion reaction of methane gas (CH4) in air .
- Step 1: We know that this reaction consumes oxygen(O2) and produces water (H2O) and carbon dioxide (CO2). Then: the reagents are CH4 and O2, and the products are H2O and CO2
- Step 2: The unadjusted chemical equation will be: CH4 + O2 —– H2O + CO2
- Step 3: Now we count the atoms of each reagent and each product and add them together: So, one moleculeof methane reacts with two molecules of oxygen to produce two molecules of water and one molecule of carbon dioxide . CH 4 + 2O 2 = 2H2O + CO 2
Classes or types of chemical reactions
Now, in thousands of experiments carried out around the world, duly repeated and controlled in the laboratory, chemical reactions can be classified into the following types:
- COMPOSITION OR SYNTHESIS REACTION: In synthesis or composition reactions is where two reactants combine to form a single product. Many elements react with one another in this way to form compounds, for example:
2CaO (s) + 2H2O (l) ——- 2Ca (OH) 2 (ac)
In this formula, 2 moles of solid calcium oxide are mixed with 2 moles of liquid water. It reacts producing 2 moles of aqueous calcium dihydroxide .
- DECOMPOSITION REACTION OR ANALYSIS: This type of reaction is contrary to that of composition or synthesis since in this 2 or more molecules do not unite to form one, but a single molecule divides or breaks to form several simpler molecules , for example:
2HgO (s) ——- 2Hg (l) + O2 (g)
In this formula one 2 molecule of solid mercury oxide decomposes or divides to form 2 molecules of mercury and one of oxygen , which are simpler than the first.
- DISPLACEMENT REACTION OR SUBSTITUTION: In this type of reaction, a free element replaces and releases another element present in a compound, its general equation is:
CuSO4 + Fe ——- FeSO4 + Cu
In this reaction one mole of copper sulfate with 1 mole of iron to form iron sulfate and copper .
- DOUBLE REPLACEMENT OR DOUBLE DISPLACEMENT: They are those reactions that occur by exchange of atoms between the reactants.
AB + CD —————– AC + BD
For Example: K2S + MgSO4! K2SO4 + MgS
In this reaction, 1 mole of potassium sulphide reacts with magnesium sulfate to form potassium sulfate and magnesium sulphide .
It is difficult to find common inorganic reactions that can be correctly classified as double substitution.
