1 / 12

Theories of Reaction Rates

Theories of Reaction Rates. Rates of Chemical Reactions. Beyond Collision Theory. For a collision to be effective, it must satisfy both of these criteria: 1. Correct orientation of reactants 2. Sufficient collision energy. Orientation of Reactants.

tracen
Download Presentation

Theories of Reaction Rates

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Theories of Reaction Rates Rates of Chemical Reactions

  2. Beyond Collision Theory • For a collision to be effective, it must satisfy both of these criteria: • 1. Correct orientation of reactants • 2. Sufficient collision energy

  3. Orientation of Reactants • Reactants must have the correct collision geometry. • If they do not, the reaction will be unable to proceed.

  4. Activation Energy • The activation energy (Ea) of a reaction is the minimum collision energy that is required for a successful reaction. • The collision energy depends on the total kinetic energy of the colliding particles.

  5. Activation Energy • Notice the following on the graph: • 1. At either temperature, only a small fraction of collisions have sufficient kinetic energy (Ea) to result in a reaction. • 2. As the temperature of a sample increases, the fraction of collisions with sufficient energy increases significantly.

  6. Transition State Theory • This is a theory that is used to predict what happens when molecules collide in a reaction. • Essentially, it shows how a molecule’s kinetic energy is converted to potential energy when it collides with another reactant. • This can all be shown using potential energy diagrams. • Remember that there is no way to predict the activation energy of a reaction from its enthalpy change.

  7. Potential Energy Diagrams

  8. Potential Energy Diagrams • The top curve on a potential energy diagram represents the transition state. The type of molecule that exists at the transition state is known as the activated complex. • The activated complex is a transitional species that is neither product nor reactant and is highly unstable.

  9. Transition State

  10. Drawing a Potential Energy Diagram • Carbon monoxide reacts with nitrogen dioxide to form carbon dioxide and nitric oxide (NO). Draw a potential energy diagram to illustrate the progress of the reaction. Label the axes, the transition state, and the activated complex. Indicate the activation energy of the forward reaction Ea(fwd) = 134kJ, as well as ∆H = -226kJ. Calculate the activation energy of the reverse reaction, Ea(rev), and show it on the graph.

  11. Drawing a potential energy diagram

  12. Homework • Practice Problems 13, 14, and 16 on page 294 • Section review: #3, 6, and 7 on page 296

More Related