18.4: Potential Energy Diagrams - Chemistry LibreTexts

Overview

• Potential energy diagrams illustrate the energy changes that occur during a chemical reaction.
• These diagrams, also known as reaction progress curves, show how the potential energy of a system changes as reactants are transformed into products.

Types of Reactions

• Endothermic Reaction

  • The energy of products is greater than the energy of reactants.
  • Enthalpy change ( \Delta H ) is positive.
  • The system absorbs energy from the surroundings (energy increase).

• Exothermic Reaction

  • The energy of products is less than the energy of reactants.
  • Enthalpy change ( \Delta H ) is negative.
  • The system releases energy to the surroundings (energy decrease).

Activation Energy

• Activation Energy (Ea)

  • Represented by the height of the hill between reactants and products on the diagram.
  • Referred to as the activation energy barrier.
  • Reacting particles must overcome this barrier when they collide to form products.

• Influence on Reaction Rate

  • Low activation energy means the reaction is likely to be fast.
  • High activation energy means the reaction is likely to be slow.

Diagrams

• Figures:
  • Potential Energy Diagram A: Represents an endothermic reaction with higher energy products.
  • Potential Energy Diagram B: Illustrates an exothermic reaction with lower energy products.
  • Activation Energy Diagrams: Compare low and high activation energy and their effects on reaction speed.

Summary

• Potential energy diagrams effectively depict the transition of reactants to products, showing the energy absorbed or released.
• They provide insights into the activation energy required and the speed of the reaction based on the energy barrier.

This content is shared under a CK-12 license and was authored by the CK-12 Foundation as part of their educational resources. The diagrams and explanations are tailored to help understand chemical kinetics and energy changes during reactions.