Collision Theory

Reaction Coordinate Diagrams

Multistep Reactions

Arrhenius Equation: Temperature and Ea Dependence

Example 1. Use the data below to find Ea.

Example 2. A reaction has Ea = 75 kJ/mol.

If k = 1.50 x 10-3 at 25 oC, what is k at 50 oC?

Example 3. A reaction doubles its rate when the temperature increases from 25 oC to 35 oC. What is the activation energy?

Reaction Mechanisms: The pathway by which a reaction proceeds from reactants to products.

• Each discrete chemical event is an “elementary step.”• The reaction is a series of elementary steps.• Steps are usually unimolecular or bimolecular.• The overall reaction is the sum of the steps.• Each elementary step goes at its own rate.• The rate of the overall reaction is the rate of the slowest (rate determining) step.

Today’s Saying

Looking dumb…

is best done alone.

Rate Laws for Elementary Steps

Overall Reaction:

Intermediates:

Catalysts: