Exothermic Reaction

Definition

An exothermic reaction is a chemical reaction that releases energy in the form of heat to the surrounding environment. These types of reactions are characterized by a decrease in the overall energy of the system, with the products of the reaction having less energy than the reactants.

5 Must Know Facts For Your Next Test

1. Exothermic reactions release heat to the surroundings, resulting in an increase in the temperature of the environment.
2. The energy released during an exothermic reaction is represented by a negative enthalpy change (ΔH < 0).
3. Exothermic reactions are favored in chemical equilibria, as they contribute to an overall decrease in the Gibbs free energy of the system.
4. Common examples of exothermic reactions include combustion reactions, acid-base neutralization reactions, and certain biological processes like cellular respiration.
5. Le Châtelier's principle states that when a system at equilibrium is subjected to a change in one of the conditions (such as temperature), the system will shift to counteract the change and re-establish equilibrium.

Review Questions

• Explain how an exothermic reaction affects the temperature of the surrounding environment.
  • In an exothermic reaction, the products of the reaction have less energy than the reactants. This excess energy is released to the surroundings in the form of heat, causing the temperature of the environment to increase. The release of heat is a key characteristic of exothermic reactions and is represented by a negative enthalpy change (ΔH < 0). This energy transfer from the system to the surroundings is a crucial factor in maintaining chemical equilibrium, as described by Le Châtelier's principle.
• Describe how the concept of exothermic reactions relates to Le Châtelier's principle in the context of shifting chemical equilibria.
  • Le Châtelier's principle states that when a system at equilibrium is subjected to a change in one of the conditions, the system will shift to counteract the change and re-establish equilibrium. In the case of exothermic reactions, an increase in temperature would favor the forward reaction, as it would release heat and help offset the temperature increase. Conversely, a decrease in temperature would favor the reverse reaction, as it would absorb heat and help restore the original temperature. This relationship between exothermic reactions and Le Châtelier's principle is crucial for understanding how changes in temperature affect the equilibrium of a chemical system.
• Analyze the role of exothermic reactions in the context of biological processes and energy production.
  • Many important biological processes, such as cellular respiration, involve exothermic reactions. In cellular respiration, the oxidation of glucose and other organic molecules releases a significant amount of energy in the form of heat. This energy is then used to drive the synthesis of ATP, the primary energy currency of the cell. The release of heat during exothermic reactions is essential for maintaining the body's temperature and providing the necessary energy for various metabolic processes. Additionally, the concept of exothermic reactions is crucial for understanding the thermodynamics of living systems and how they harness and utilize energy to sustain life.

Related terms

Endothermic Reaction: An endothermic reaction is a chemical reaction that absorbs energy in the form of heat from the surrounding environment. These reactions result in an increase in the overall energy of the system, with the products having more energy than the reactants.

Enthalpy: Enthalpy is a measure of the total energy of a thermodynamic system, including the internal energy and the work done by or on the system due to changes in pressure or volume.

Thermodynamics: Thermodynamics is the branch of physics that deals with the relationships between heat, work, temperature, and energy. It describes the transfer of energy from one form to another and how it affects the state of matter and energy in the universe.