Examples of Exothermic Reactions

Oct 13, 2025 by pynkocean.com 11 views

In chemistry, an exothermic reaction is a type of chemical reaction that releases heat energy into the surroundings. This type of reaction is often characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. In this article, we will examine four different reactions and determine which one is exothermic.

What is an Exothermic Reaction?

An exothermic reaction is a chemical reaction that releases heat energy into the surroundings. This type of reaction is often characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. Exothermic reactions can be classified into two main categories: combustion reactions and decomposition reactions.

Combustion Reactions

Combustion reactions are a type of exothermic reaction that involves the reaction of a fuel with oxygen to produce heat and light. Examples of combustion reactions include the burning of gasoline, the burning of wood, and the combustion of coal. Combustion reactions are often characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy.

Decomposition Reactions

Decomposition reactions are a type of exothermic reaction that involves the breakdown of a compound into simpler substances. Examples of decomposition reactions include the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2), and the decomposition of ammonia (NH3) into nitrogen (N2) and hydrogen (H2). Decomposition reactions are often characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy.

Examples of Exothermic Reactions

Now that we have discussed what an exothermic reaction is and the different types of exothermic reactions, let's examine four different reactions and determine which one is exothermic.

Reaction A: $CH_4 + 2 O_2 \rightarrow CO_2 + 2 H_2O + 891 \text{ kJ}$

Reaction A is a combustion reaction that involves the reaction of methane (CH4) with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O). The reaction is characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. The reaction is also characterized by a positive value for the heat of reaction (Q), which indicates that the reaction is releasing heat energy into the surroundings.

Reaction B: $NH_4NO_3 + H_2O + 25 \text{ kJ} \rightarrow NH_4^{+}(aq) + NO_3^{-}(aq)$

Reaction B is a decomposition reaction that involves the breakdown of ammonium nitrate (NH4NO3) into ammonium ions (NH4+) and nitrate ions (NO3-). The reaction is characterized by a positive value for the heat of reaction (Q), which indicates that the reaction is releasing heat energy into the surroundings. However, the reaction is not characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is not releasing energy.

Reaction C: $2 H_2O + 286 \text{ kJ} \rightarrow 2 H_2 + O_2$

Reaction C is a decomposition reaction that involves the breakdown of water (H2O) into hydrogen gas (H2) and oxygen gas (O2). The reaction is characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. The reaction is also characterized by a positive value for the heat of reaction (Q), which indicates that the reaction is releasing heat energy into the surroundings.

Reaction D: $CaCO_3 \rightarrow CaO + CO_2$

Reaction D is a decomposition reaction that involves the breakdown of calcium carbonate (CaCO3) into calcium oxide (CaO) and carbon dioxide (CO2). The reaction is characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. The reaction is also characterized by a positive value for the heat of reaction (Q), which indicates that the reaction is releasing heat energy into the surroundings.

Conclusion

In conclusion, Reaction A is the only reaction that is exothermic. The reaction is characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. The reaction is also characterized by a positive value for the heat of reaction (Q), which indicates that the reaction is releasing heat energy into the surroundings.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
Chang, R. (2010). Chemistry (10th ed.). McGraw-Hill.
Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2011). General chemistry: Principles and modern applications (10th ed.). Pearson Education.

What is an Exothermic Reaction?
Combustion Reactions
Decomposition Reactions
Examples of Exothermic Reactions
Conclusion
References

Keywords

Exothermic reaction
Combustion reaction
Decomposition reaction
Enthalpy
Heat of reaction
Chemical reaction
Thermodynamics
Frequently Asked Questions (FAQs) About Exothermic Reactions ====================================================================

In this article, we will answer some of the most frequently asked questions about exothermic reactions. Whether you are a student, a teacher, or a professional in the field of chemistry, this article will provide you with the information you need to understand exothermic reactions.

Q: What is an exothermic reaction?

A: An exothermic reaction is a type of chemical reaction that releases heat energy into the surroundings. This type of reaction is often characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy.

Q: What are some examples of exothermic reactions?

A: Some examples of exothermic reactions include:

Combustion reactions, such as the burning of gasoline or wood
Decomposition reactions, such as the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2)
Neutralization reactions, such as the reaction between acid and base

Q: What is the difference between an exothermic reaction and an endothermic reaction?

A: An exothermic reaction is a type of chemical reaction that releases heat energy into the surroundings, while an endothermic reaction is a type of chemical reaction that absorbs heat energy from the surroundings. In other words, an exothermic reaction is a reaction that releases energy, while an endothermic reaction is a reaction that absorbs energy.

Q: How do I determine if a reaction is exothermic or endothermic?

A: To determine if a reaction is exothermic or endothermic, you need to look at the change in enthalpy (ΔH) for the reaction. If the change in enthalpy is negative, the reaction is exothermic. If the change in enthalpy is positive, the reaction is endothermic.

Q: What are some common applications of exothermic reactions?

A: Some common applications of exothermic reactions include:

Power generation: Exothermic reactions can be used to generate electricity in power plants.
Chemical synthesis: Exothermic reactions can be used to synthesize chemicals, such as plastics and pharmaceuticals.
Food processing: Exothermic reactions can be used to cook food and to preserve food.

Q: What are some safety precautions that I should take when working with exothermic reactions?

A: When working with exothermic reactions, you should take the following safety precautions:

Wear protective clothing, such as gloves and goggles.
Work in a well-ventilated area.
Use a thermometer to monitor the temperature of the reaction.
Have a fire extinguisher nearby.

Q: Can exothermic reactions be used to generate electricity?

A: Yes, exothermic reactions can be used to generate electricity. This is known as a thermoelectric generator. The heat from the exothermic reaction is used to generate electricity.

Q: Can exothermic reactions be used to synthesize chemicals?

A: Yes, exothermic reactions can be used to synthesize chemicals. This is known as a chemical synthesis reaction. The heat from the exothermic reaction is used to drive the reaction forward.

Q: Can exothermic reactions be used to cook food?

A: Yes, exothermic reactions can be used to cook food. This is known as a thermal cooking reaction. The heat from the exothermic reaction is used to cook the food.

Conclusion

In conclusion, exothermic reactions are an important type of chemical reaction that can be used to generate electricity, synthesize chemicals, and cook food. By understanding the basics of exothermic reactions, you can use them to solve a wide range of problems.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
Chang, R. (2010). Chemistry (10th ed.). McGraw-Hill.
Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2011). General chemistry: Principles and modern applications (10th ed.). Pearson Education.

What is an Exothermic Reaction?
Examples of Exothermic Reactions
Difference Between Exothermic and Endothermic Reactions
Determining if a Reaction is Exothermic or Endothermic
Common Applications of Exothermic Reactions
Safety Precautions for Exothermic Reactions
Conclusion
References

Keywords

Exothermic reaction
Combustion reaction
Decomposition reaction
Enthalpy
Heat of reaction
Chemical reaction
Thermodynamics
Power generation
Chemical synthesis
Food processing
Safety precautions