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What does one mean by Exothermic and Endothermic Reactions? Give Examples

By BYJU'S Exam Prep

Updated on: September 13th, 2023

Exothermic reactions release heat to the surroundings, while endothermic reactions absorb heat from the surroundings. Exothermic reactions are characterized by the release of energy in the form of heat. These reactions are often spontaneous and self-sustaining. Some examples of exothermic reactions are Combustion and neutralization.

On the other hand, endothermic reactions absorb energy from the surroundings, typically in the form of heat. Some examples of endothermic reactions are photosynthesis and the melting of ice cubes.

Exothermic and Endothermic Reactions

Now that you know what is meant by exothermic and endothermic reactions, we can dive deeper. An exothermic reaction is a chemical reaction that releases energy in the form of heat to the surroundings. In these reactions, the products have lower energy than the reactants, and the excess energy is released as heat.

Thus, we can illustrate an exothermic reaction as: 

Reactants —> Products + Energy

An endothermic reaction is a chemical reaction that absorbs energy from the surroundings in the form of heat. In these reactions, the products have higher energy than the reactants, and the additional energy is obtained from the surroundings.

Thus, we can illustrate an exothermic reaction as: 

Reactants + Energy —> Products

Examples of Exothermic and Endothermic Reactions

Example of Exothermic Reaction: A mixture of sodium and chlorine to yield table salt produces 411 KJ of energy for each mole of salt produced.

2Na(s) + Cl2(s) –> 2NaCl(s) + energy

Example of Endothermic Reaction: Ammonium chloride dissolved in water dissociates into ammonium and chloride ions by absorbing heat from the surroundings.

NH4Cl (s) + H2O (l) ⟶ NH4Cl (aq) – Heat

These chemical reactions lower the temperature of their surrounding area, thereby creating a cooling effect. The temperature of an isolated system decreases while the surroundings of a non-isolated system gain heat, resulting in an overall positive quantity for the heat of the reaction.

Summary:

What does one mean by Exothermic and Endothermic Reactions? Give Examples

An exothermic reaction is a reaction that involves the release of energy in the form of light or heat and an endothermic reaction is a reaction that involves the absorption of energy in the form of heat. Some examples of exothermic reactions include the process of combustion and neutralization in a chemical reaction. Some examples of endothermic reactions include the process of photosynthesis in plants and the dissolving of Ammonium Nitrate.

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