1. Reaction Rates
Notes#12
Chapter 17

2. Reaction Processes & Rates
Reactions are written in simplified forms-showing reactants turning into products
reactants → products
Real reactions are more complex
Elevated energy states, and temporary substances (activated complex) are the rule
Some reactions → more complex→ several distinct steps

3. Reaction Rates Chemical reaction rates vary widely
Some reactions are completed within a few milliseconds
Others require thousands of years
Most Reactions start off relatively rapidly, slow steadily, and become very slow as they approach completion
Some reactions simply stop at completion. Others level out at an equilibrium with their reverse reactions (forward & reverse rates equal)

4. Reaction rate Average rate at which reactants produce products
CO(g) + NO2(g) → CO2(g) + NO(g)
Reaction rate =∆quantity
∆time
Time (s)
[NO] (M)
0.00s
0.00
2.00s
.010

5. Pg. 531
Practice problems 1,3

6. Collision Theory
Explains chemical reactions in terms of effective collisions between particles.
-sufficient energy
-favorable orientation
Conditions that favor effective collisions, favor reactions.
Increasing Temperature (& pressure) increase the frequency & energy of collisions… favoring most reactions

7. Activation Energy, Activated Complexes
Most physical & chemical changes require an input of energy to breakdown older structures
Bonds within reactants are broken down with a specific amount of energy called Activation Energy .
Activation energy – is amount of energy to activate the reaction, get it going
energized, broken down reactants → temporary activated complexes → products

8. Activated Complexes Reactants+EnergyActivated complex
Internal Energy ‘Peaks’ in this complex, then starts to drop as more stable products begin forming.
Activated Complex  Products + Energy
Draw 2 graphs

9. Reaction Rates (5 factors affecting rates)
1. Substances involved & Reaction Type * Ions in solution react very fast * Most metals corrode slowly
2. Temperature = Kinetic Energy higher temp. speeds up most reactions
3. Concentration reactions go faster at higher concentrations (more effective collisions)

10. Reaction Rates (5 factors affecting rates) Continued
4. Contact Area (surface area, mixing) fine powder, versus large pellets into liquid
5. Catalysts-substances that promote or speed up reactions without themselves being consumed. Catalysts lower activation energy. Enzymes are a type of catalyst