Exothermic Reaction is a chemical reaction that releases energy in the form of heat to its surroundings. Common examples of exothermic reactions include combustion reactions, where substances burn and produce heat as a byproduct, such as the burning of wood or the combustion of gasoline in an engine.

In this article, we will discuss the concept of Exothermic Reaction in detail including its definition, example, exothermic chemical reactions, its graph, as well as its differences from endothermic reactions.

What is an Exothermic Reaction?

Exothermic Reaction is a chemical reaction that releases energy in the form of heat/light or sound to its surroundings. During this chemical reaction, the system loses heat to the surroundings, resulting in a temperature increase in the surrounding environment. The word Exothermic is derived from the Greek words “exo,” meaning outside/leave, and “therme,” meaning heat. For example, Burning of a candle releases heat and light energy in the surroundings is an exothermic reaction.

A + B (Reactants) → AB (Products) + Energy Release

In an exothermic reaction, the total energy of the products of the reaction is lower than the total energy of the reactants. As a result, the excess energy is released into the surrounding environment, usually in the form of heat.

Definition of Exothermic Reaction

Exothermic Reaction is a chemical reaction that releases energy in the form of heat/light or sound to its surroundings.

Characteristics of Exothermic Reaction

Various uses of characteristic s of Exothermic Reactions are,

• Formation of products with lower energy than the starting reactants materials, causing a net release of heat in the surrounding causing the increase of temperature.
• So the overall energy of the system will decrease notably from the reactants to the products.
• Exothermic Reaction play role in making a gas molecule from atoms.
• Exothermic Reaction play role in rain forming from water vapor in clouds
• In an exothermic reaction, the change in enthalpy ( ΔH) will be negative.

Examples of Exothermic Reaction

Most common examples of exothermic reaction are given below:

• Combustion Reaction
• Neutralization Reaction
• Corrosion Reaction
• Chemical composition

Combustion Reaction

The reaction of burning of carbon-containing compounds by using oxygen, from air, and produces carbon dioxide, water, and Energy are called Combustion Reaction.

Fuel + O₂ → CO₂ + H₂O + Energy

Some examples of combustion are,

The burning of natural gas methane is also an example of an exothermic reaction. Given below is the reaction.

CH₄ + 2O₂ → CO₂ + 2H₂O + Energy

Combustion of glucose, given by the following reaction:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Neutralization Reaction

Neutralization reaction is also a common example of exothermic reaction in daily life. when an acid and a base are combined. There H⁺ and OH^– ions are released, these ions combine to form water. In any neutralization process, the products are always water and some form of an ionic salt.

A general example of a neutralization Reaction is given below.

Acid + Base → Salt + Water + Energy

Some examples of Neutralization Reaction are,

The reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is an exothermic neutralization reaction. It forms common table salt (NaCl) and water

HCl + NaOH → NaCl + H₂O + Energy

Acetic acid reacts with ammonium hydroxide to produce ammonium acetate, water and energy.

CH₃COOH + NH₄OH → NH₄CH₃COO + H₂O + Energy

Chemical Decomposition

A chemical decomposition reaction can be define as it is a reaction in which a compound breaks down into two or more simpler substances. The starting materials are called reactants while final materials are called products. These reaction are mostly Exothermic but some may be endothermic.

AB → A + B + Energy

Example:

• Decomposition of NO: 2NO → N₂ + O₂ + Energy

• Decomposition of Ozone: 2O₃ → 3O₂ + Energy

Corrosion Reaction

Corrosion Reaction is also example of exothermic reaction. It is destructive process that damages the surface of metal. This deterioration is occurs because of oxidation of the metal atoms due to environmental exposure.

The general example of Corrosion exothermic reaction is given below.

Metal atoms + Oxygen → Metal oxide + Energy

• Iron Rusting is common example of corrosion in daily life.

4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ + Energy

Exothermic Reaction Graph

In an exothermic reaction, the products of the reaction have lower chemical potential energy than the reactants. This energy difference is released in the form of heat. The graph for the same is added below,

Energy Change in Exothermic Reactions

In Exothermic reaction atomic bonds of reactants break and energy is released. It mean that the total energy of the products is less than the total energy brought to the system by the reactants. An exothermic reaction equation will show heat as one of its products.

A + B → AB + Heat → -ΔH^⚬

In the formation of products with lower energy than the starting reactants materials, causing a net release of heat in the surrounding causing the increase of temperature. So the overall energy of the system will decrease notably from the reactants to the products.

Exothermic Reaction vs Endothermic Reaction

Various differences between Endothermic and Exothermic Reactions are added in the table below as,

Endothermic and Exothermic Reaction Graph

The endothermic and exothermic reaction graph is added below,

Formula for Heat in Exothermic Reactions

The total energy of the products is less than the total energy brought to the system by the reactants in an exothermic reaction and the formula for the same is,

ΔH^⚬ = Total Bond Energy of Reactants – Total Bond Energy of Products

How Can We Measure Energy Release in Exothermic Reaction?

As it is not technically feasible to measure how much energy is released in a chemical reaction, the change in energy is measured instead. It is measure by calculated difference between the energy of the products reacting and the energy released after the reaction.

However a device called calorimeter is used to measure the energy produced in an exothermic reaction. A widely used calorimeter, known as the bomb calorimeter, is a relatively simple tool used to measure released energy.

Conclusion on Exothermic Reaction

Exothermic Reaction is a chemical reaction that releases energy in the form of heat/light or sound to its surroundings. During this chemical reaction, the system loses heat to the surroundings, resulting in a temperature increase in the surrounding environment. In this chemical reaction atomic bonds of reactants break. Calorimeter is used to measure the energy produced in an exothermic reaction.

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Exothermic Reactions-FAQs

What is an Exothermic Reaction?

The reaction that releases heat or light to its surroundings are called Exothermic Reactions.

What are Examples of Exothermic Reactions?

Some examples of Exothermic reactions are Combustion Reaction, Neutralization Reaction, Respiration, Formation of Snow and Corrosion Reaction.

What is Sign of Enthalpy Change for an Exothermic Reaction?

The change in enthalpy ( ΔH) for an exothermic reaction will be negative. As energy is released.

Is Respiration Exothermic Reaction or Endothermic Reactions?

Respiration is exothermic reaction, because energy is release in these reaction. The reaction for the same is, C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Which Process is Exothermic?

The process which releases energy in the form of heat/light or sound to its surroundings. Water freezing into ice is exothermic process. As water releases heat into its surroundings.

What Happens in an Exothermic Reaction?

In an Exothermic Reaction bonds are broken between the atoms of the reactants that releases the energy in the form of heat, light, sound, or electricity.

Why is Respiration Considered an Exothermic Reaction Class 10?

Respiration is considered to be an exothermic reaction because in respiration process heat is released.