Equilibrium Study Guide

Equilibrium Study Guide: Mastery Topics and Skills

Fundamental Concepts

  • Reactions and Particle Collisions

    • Reactions occur when particles collide with one another.

    • For an effective collision that can lead to a reaction, the particles must meet two criteria:

    • Proper energy

    • Proper orientation

  • Collision Frequency and Reaction Rate

    • The rate of reaction increases with the number of collisions.

    • More collisions result in a higher (faster) reaction rate.

Six Factors Affecting Reaction Rate

  • 1. Type of Substance

    • Comparison between ionic and nonionic substances:

    • Ionic compounds have a faster reaction rate compared to nonionic compounds.

  • 2. Temperature

    • Increasing the temperature typically increases the reaction rate.

  • 3. Pressure (for Gases)

    • Increasing the pressure also results in a higher reaction rate, particularly for gaseous reactions.

  • 4. Concentration

    • An increase in concentration leads to an increased reaction rate.

  • 5. Surface Area

    • Enlarging the surface area of reactants boosts the reaction rate.

  • 6. Catalyst

    • The addition of a catalyst can enhance the reaction rate.

Definition and Role of Catalysts

  • Catalyst:

    • A substance that accelerates the reaction rate without being consumed in the reaction.

    • Catalysts increase the reaction rate by lowering the activation energy, which is the energy required to initiate the reaction.

Le Chatelier's Principle

  • Definition:

    • If a system at equilibrium is subjected to a stress (change in conditions), the equilibrium position will shift to counteract that stress, thus restoring a new equilibrium.

  • Types of Stress

    • Changes in temperature

    • Changes in concentration

    • Changes in pressure (applicable to gases only)

The Bathtub Model

  • Ability to predict the directional shift of equilibrium when a stress is applied to the system based on the principles of Le Chatelier.

Catalyst Effects on Equilibrium

  • Adding a catalyst does not shift the position of equilibrium.

    • Catalysts increase the rate of both forward and reverse reactions equally, resulting in no net change in the direction of the equilibrium.

Potential Energy Diagrams (PE Diagrams)

  • Overview:

    • These diagrams illustrate the change in potential energy throughout the progression of a reaction.

  • Key Components of a PE Diagram

    1. Activation Energy:

    • The energy necessary to initiate the reaction.

    1. Activated Complex:

    • The peak energy point in the reaction, where breaking and reforming of bonds occur; this is where the transformation from reactants to products takes place.

    1. Heat of the Products / Heat of the Reactants:

    • The measure of potential energy possessed by reactants versus products; shows how much energy the reactants start with compared to that of the products at completion.

    1. Heat of Reaction:

    • The total energy change (loss or gain) during a chemical reaction; represented by the gap between the energy levels of products and reactants.

    1. Addition of a Catalyst:

    • Indicators how a catalyst lowers the activation energy, while leaving the final energy levels (ends of the diagram) unchanged.