1. Reaction Process

2. A reaction mechanism is a step by step sequence of reactions that show an overall chemical change
The same reaction can occur by different pathways under different conditions.
A species that appears in some steps but not in the overall equation is called an intermediate

3. . Step 1 I2 ↔ 2I Step 2 2I + H2 ↔ 2HI I2 + H2 ↔ 2HI
A simple looking reaction like I2 + H2  2HI is more complex than it appears. This reaction has 2 possible reaction pathways.
Step 1
I2 ↔ 2I
Step 2
2I + H2 ↔ 2HI
I2 + H2 ↔ 2HI

4. A second pathway is as follows
Step 1
I2 ↔ 2I
Step 2
I + H2 ↔ H2I
Step 3
H2I + I ↔ 2HI
I2 + H2 ↔ 2HI

5. Homogenous reaction – reaction exists in a single phase
Heterogenous reaction – reaction is made up of materials in different phases

6. Collision theory is an attempt to understand what happens to the individual molecules during a reaction. Molecules must have the proper energy and orientation for a reaction to occur.
You need enough activation energy to create enough high energy collisions to get a reaction started.
Once an exothermic reaction starts, it will sustain itself

7. An activated complex is an intermediate material
An activated complex is an intermediate material. You need enough activation energy to create the activated complex.

8. Reaction rates
Reaction rate is the change in concentration of the reactants per unit of time
Factors that influence reaction rates – presence of a catalyst, surface area, temperature, concentration
A catalyst is a substance that speeds up a reaction without being consumed itself

9. Experiments are conducted to find rate laws
The slowest step in any reaction is called the rate determining step
A rate law is an equation the relates the reaction rate to the reactants