Types of Chemical Reactions
Last Updated : 10 Apr, 2025
Types of Chemical Reactions as the name suggests explores the classification of various types of chemical reactions based on different parameters. As we are surrounded by chemical reactions in our daily lives. From burning a match stick to making food all of the things and events in our lives involve various types of chemical reactions. Understanding the different types of chemical reactions is key to understanding how matter changes and interacts with one another. From combustion reactions that power our cars and homes, to acid-base reactions that occur in our bodies and the natural world, there are many different types of chemical reactions with a wide range of applications
Combination, decomposition, single-replacement, double-replacement, redox, combustion, precipitation, neutralization, etc. are some of the types of chemical reactions using various parameters as the basis. In this article, we will learn about it all the types of chemical reactions and the various bases for these classifications of chemical reactions as well.
What is Chemical Reaction?
A chemical reaction is a process in which the bonds are broken within reactant molecules, and in order to form a new substance which is the result of new bonds formation in product molecules. This can be seen in a chemical reaction as the change in state, change in color, the evolution of gas, and change in temperature.
The changes in the chemical reaction can be classified as physical or chemical change, and the detailed description of the same is as follows:
- Physical change: When a usually reversible change in the physical properties of a substance, as size or shape takes place. Freezing a liquid, melting of candle, crushing a can, shredding papers all are examples of physical change.
- Chemical change: When a chemical property of matter changes it is a type of chemical change such properties are density change, change in temperature, energy change etc, It is commonly called a chemical reaction. Combustion, rusting, fermentation, etc. are examples of chemical change.
Characteristics of a Chemical Reaction
| Characteristic | Description | Example |
|---|
| Evolution of Gas | Occurs when a gas is released during a reaction. | Zinc reacts with hydrochloric acid to produce hydrogen gas and zinc chloride: Zn + 2HCl → ZnCl2 + H2 |
| Change in Color | Characterized by a visible alteration in color. | Lead nitrate and potassium iodide react to form a yellow precipitate of lead iodide and colorless potassium nitrate: Pb(NO3)2 + 2KI → PbI2 (yellow precipitate) + 2KNO3 |
| Change in Temperature | Accompanied by a detectable temperature shift, indicating exothermic or endothermic reactions. | Varied, depending on whether the reaction absorbs or releases energy. |
| Change in Energy | Involves energy either being released or absorbed. | Combustion reactions release energy, e.g., burning fuel. |
| Formation of Precipitate | Involves solid formation from a liquid solution. | Barium chloride reacts with sodium sulfate to form barium sulfate precipitate and sodium chloride: BaCl2 + Na2SO4 → BaSO4 (precipitate) + NaCl |
| Change in State | Involves a transition from one state of matter to another. | Ammonia gas reacts with hydrogen chloride gas to form solid ammonium chloride: NH3(g) + HCl(g) → NH4Cl(s) |
Types of Chemical Reactions
Based on the different properties, types of change or reactants and products, we can classify chemical reactions. Some of these classifications on various basis are as follows:
Based on Product and Reactant
Based on the formation of different kinds of products or change in the condition of reactants, different types of chemical reactions are:
- Combustion reaction
- Neutralization reaction
- Decomposition reaction
- Redox Reaction
- Double-Displacement Reaction
Combination Reaction
In the Combination Reaction, two or more reactants combine together to form a single product. As in this reaction, new compounds are formed with the help of other compounds, so it is also called a synthesis reaction.
Some Examples of combination reactions are as follows:
- Reaction of quick lime (Calcium Oxide) with water, results in calcium hydroxide,
CaO(s)+H2O(l)→Ca(OH)2(aq)
- Reaction of sulfur trioxide gas with water results in sulfuric acid,
SO3(g)+H2O(l)→H2SO4(aq)
Note: This reaction is the reason behind the acid rain, as oxides of sulfur and nitrogen reaction with water in the atmosphere the acid produces and this acid-infused rain poured down on the surface of the earth which is called acid rain.
Decomposition Reaction
In the Decomposition reaction, a single component breaks down into two or more products, to break the bonds between different components a lot of heat is required, we can provide it in the form of heat, electricity or sunlight, etc.
Some examples of decomposition reactions are as follows:
- Decomposition of carbonic acid,
H2CO3(aq) → H2O(l) + CO2(g)
- Decomposition of Nickel (III) Oxide,
2Ni2O3(aq) → 4Ni(s) + 3O2(g)
- The decomposition of calcium carbonate (CaCo3) gives CaO (Quick Lime) which is a major component of cement.
CaCO3(s) heat > CaO(s) + CO2(g)
- Calcium hydroxide (Slaked lime) on decomposition gives Quick lime (CaO).
Ca(OH)2 heat> CaO(s) + H2O (l)
Redox Reaction
Redox Reaction which is also called Reduction-oxidation reaction is the reaction, in which reduction(gain of the electron) and oxidation (loss of electron) takes place simultaneously. So in other words, it is the process of transfer of electrons between different elements and compounds to form new compounds.
Consider an example of an electron-chemical cell-like redox reaction between Zinc and Hydrogen.
Zn + 2H+ → Zn2+ + H2
For example, take the reaction of Iron with copper sulfate,
CuSO4 (aq) + Fe(s) → FeSO4 (aq) + Cu(s)
In the above reaction, a Zinc atom reacts with two positively charged hydrogen to which electrons get transferred from the zinc atom and hydrogen becomes a stable molecule and Zinc ion as the product.
- Oxidation - Oxidation is a loss of electrons and the oxidation state of given reactant increases. In the above reaction, copper goes through oxidation as it gains electrons and is a reducing agent in this example.
- Reduction - Reduction is a gain of electrons and the reactant state of a given reactant decreases. In the above reaction, iron goes through reduction as it losses electrons and is an oxidizing agent in this example.
Single Displacement Reaction
In a Single Displacement Reaction, more reactive metal displaces less reactive metal from its salt or other compounds. In these reactions, through reactivity series, products can be determined. Reactivity series is a series of elements in which elements are arranged in decreasing order of their reactivity. Thus, the elements present at the top of the series are more reactive than the elements present at the bottom of the series.
For example, take the reaction between potassium and magnesium chloride (MgCl2).
2K + MgCl2 → 2KCl + Mg
In this reaction, potassium displaces magnesium from its salt because of the more reactivity of potassium than magnesium. Potassium is present at the top of the reactivity series and hence, it is the most reactive element.
Some more examples of Single Displacement Reactions include:
- Zinc reacting with hydrochloric acid to produce zinc chloride and hydrogen gas:
Zn + 2HCl → ZnCl2 + H2
- Iron reacting with copper sulfate to produce copper and iron sulfate:
Fe + CuSO4 → Cu + FeSO4
- Zinc reacting with silver nitrate to produce zinc nitrate and silver:
Zn + 2AgNO3 → Zn(NO3)2 + 2Ag
Double-Displacement Reaction
It is a kind of displacement reaction in which two chemical species react and consequently, their ions i.e. cations and anions switch places forming two new products. now look at the reaction between silver nitrate and sodium chloride. The products of the reaction will be silver chloride and sodium nitrate after the double-displacement reaction.
Examples of double displacement reactions are as follows:
- Reaction between silver nitrate and sodium chloride, results in silver chloride and sodium nitrate,
AgNO3 (aq) + NaCl (s) → AgCl (aq) + NaNO3 (s)
- Reaction between potassium nitrate and aluminium chloride, results in aluminium nitrate and potassium chloride,
KNO3 + AlCl3 → Al(NO3)3 + KCl
- Reaction between sodium sulfate and barium chloride, results in barium sulfate and sodium chloride.
Na2SO4 (aq) + BaCl2 (aq) → BaSO4 (s) + 2NaCl(aq)
Based on Heat Involved in Reaction
Based on the heat involved in the chemical reaction, Reactions can be classified into two categories:
- Exothermic Reaction
- Endothermic Reaction
Exothermic reaction
Chemical reactions in which heat energy is released are known as exothermic reactions. The burning of methane gas in the presence of air produces heat energy. All the combustion reactions are exothermic.
For example, the combustion of ethane gives Carbon dioxide and water with some heat as well
2C2H6 (s) + 5O2 (g) → 2CO2(g) + 6H2O (g) + heat
Endothermic reaction
Chemical reactions that involve the absorption of energy are known as endothermic reactions.
Example: Formation of nitric oxide during the reaction of nitrogen and oxygen.
N2 (g) + O2 (g) + Heat → 2NO
Check, Difference between Exothermic and Endothermic Reactions
Some Other Chemical Reactions
Other than all the above-mentioned types, there are some more important types of reactions that are used throughout the study of chemistry. These types are explained as follows:
Precipitation Reaction
A precipitation reaction is a type of chemical reaction that occurs when two solutions are mixed and a solid substance (precipitate) is formed as a result of the reaction. In this type of reaction, the ions of two different aqueous solutions react with each other to form an insoluble solid. This solid substance is called a precipitate and it settles at the bottom of the container.
An example of a precipitation reaction is the reaction between silver nitrate (AgNO3) and sodium chloride (NaCl):
AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3 (aq)
In this reaction, silver nitrate and sodium chloride are mixed together, and the silver ions (Ag+) and chloride ions (Cl-) react with each other to form solid silver chloride (AgCl), which appears as a white precipitate. The sodium and nitrate ions remain in the solution as they do not react with each other.
Neutralization Reaction
A Neutralization reaction is a reaction between an acid and a base to give salt and water as the products. The formation of the water molecules is by the combination of OH– ions and H+ ions. The overall pH of the products when a strong base and a strong acid undergo a neutralization reaction must be 7. Consider the example of the neutralization reaction between Hydrochloric acid (HCl) and Sodium Hydroxide (NaOH) giving out sodium chloride (Common Salt) and water.
HCl (l) + NaOH (aq) → NaCl (aq) + H2O (l)
Combustion Reaction
A combustion reaction is a type of chemical reaction between a fuel and an oxidant that produces a product called ad oxidized product. an oxidizer is a chemical fuel required to burn such as oxygen. Generally, it's a reaction between hydrocarbon and oxygen to yield carbon dioxide, water, and heat.
Hydrocarbon + Oxygen → Carbon dioxide + Water + Heat
For example, consider the combustion of methane gas,
CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (g) + Heat
Combustion of Magnesium ribbon,
2Mg + O2 → 2MgO + Heat
Read More,
Common Chemical Reactions
This table presenting common chemical reactions and their equations:
| Reaction Description | Chemical Equation |
|---|
| Combustion of Hydrogen | 2H2(g)+O2(g) →2H2O(g) |
| Photosynthesis | 6CO2(g)+6H2O(l)+light energy →C6H12O6(s)+6O2(g) |
| Electrolysis of Water | 2H2O(l) →2H2(g)+O2(g) |
| Respiration | C6H12O6(s)+6O2(g) →6CO2(g)+6H2O(l)+energy |
| Rusting of Iron | 4Fe(s)+3O2(g)+2nH2O(l) →2Fe2O3⋅nH2O(s) |
| Reaction of Quicklime with Water | CaO(s)+H2O(l) →Ca(OH)2(s) |
| Decomposition of Lead Nitrate | 2Pb(NO3)2(s) →2PbO(s)+4NO2(g)+O2(g) |
| Decomposition of Ferrous Sulfate | 2FeSO4(s) →Fe2O3(s)+SO2(g)+SO3(g) |
| Displacement Reaction of Iron and Copper Sulfate | Fe(s)+CuSO4(aq) →FeSO4(aq)+Cu(s) |
| Reaction of Hydrogen Gas with Pure Hydrogen | H2(g)+catalyst → exothermic release |
Sample Questions on Types of Chemical Reactions
Question 1: Guess the type of reaction given below:
CH4 + 2O2 ⇢ CO2 + 2H2O + Energy
Answer:
The above two reactions are combustion reaction.
Question 2: Define exothermic and endothermic reactions.
Answer:
An exothermic reaction is a reaction in which there is an release of energy which can be in the form of light or heat. Few examples are nuclear fission, rusting of iron.
On the other hand, an endothermic reaction is the reaction in which the system absorbs heat from the surrounding in the form of heat. Few examples are melting of ice, cooking etc.
Question 3: Define the term Reactant and Product.
Answer:
Reactant- The molecules or chemical species that react to form a product is known as reactant.
Product- The resultant species that formed after the reaction is known as Product.
Question 4: In the given reaction, identify the substance which gets oxidized and which gets reduced:
MnO2 + 4HCl → 2H2O + Cl2
Answer:
In the above equation HCl is oxidized to Cl2 and MnO2 is reduced to H2O, hence HCl is oxidized and MnO2 is reduced in the above reaction.
Question 5: Find the oxidizing agent for the following reaction:
H2S + I2 → 2HI + S.
Answer:
Addition of hydrogen is known as reduction whereas the reactant which get reduced is known as oxidizing agent. It is clear that I2 is reduced and hence it is an oxidizing agent.
Question 6: Why does the color of copper sulfate (CuSo4) solution change when an iron nail is dipped in it?
Answer:
When an iron nail is dipped in copper sulfate (CuSO4) solution, the displacement reaction takes place. The color of copper sulfate solution disappears due to the formation of light green solution of iron sulfate.
Fe(S) + CuSO4(aq) ⇢ FeSO4(aq) + Cu(S)
Question 7: Which reaction is called the opposite of combination reactions? Write equations for these reactions.
Answer:
Decomposition reaction, is known as the opposite of combination reactions, In this reaction single compound breaks down to produce two or more simpler substances.
For example, decomposition of Water, when electricity is conducted through the water using electrodes.
2H2O (l) + Electricity ⇢ 2H2 (g) + O2 (g)
On the contrary, in combination reaction when two or more substances combine to form a new substance.
For example,
2H2 (g)+ O2 (g) ⇢ 2H2O(l)
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