Unit 7 Notes

Part 1

Chemical Kinetics• The area of chemistry

concerned with the speed at which reactions occur is called chemical kinetics.

– Reaction rate is the change in concentration of reactants and products in a certain amount of time.

Average rate of reaction = Δ [reactant or product]

Δ time

Collision Theory

Key Idea: Molecules must collide to react.

•In order to react molecules and atoms must come in

contact with each other.

•They must hit each other hard enough to react.

•Anything that increase these will make the reaction

occur faster.

Ene

rgy

Reaction coordinate

Reactants

Products

Ene

rgy

Reaction coordinate

Reactants

Products

Activation Energy - Minimum energy to make the reaction happen

Ene

rgy

Reaction coordinate

Reactants

Products

Overall energy change

Endothermic Reactions

Exothermic Reactions

Your To-Do List for Today• Work independently and quietly! • In your books:

• Read & take notes on “Reaction Rates” on pg. 722-724

• Answer Question #1 on pg 731

• Read & take notes on 22-2 on pg. 732-737

• Answer Questions #1,2,5 on pg. 737

• Read & take notes on 22-3 on pg. 738-743

• Answer Questions #1-3

• DUE MONDAY!!

2NO2(g) 2NO(g) + O2(g)Reaction Rates:

2. Can measure appearance of products

1. Can measure disappearance of reactants

3. Are proportional stoichiometrically

DMA#8 4/15/13Name 3 things that could increase the rate at which a chemical reaction happens.

4th Period- Get out homework for grading!

Catalysis

•Catalyst: A substance that speeds up a reaction without being consumed

•Enzyme: A large molecule (usually a protein) that catalyzes biological reactions.

Pt surface

HH

HH

HH

HH

• Hydrogen bonds to surface of metal.

• Break H-H bonds

Catalysts

Pt surface

HH

HH

Catalysts

C HH C

HH

Pt surface

HH

HH

Catalysts

C HH C

HH

• The double bond breaks and bonds to the catalyst.

Pt surface

HH

HH

Catalysts

C HH C

HH

• The hydrogen atoms bond with the carbon

Pt surface

H

Catalysts

C HH C

HH

H HH

Catalysts increase the number of effective collisions.

Catalysis

Catalysis

Exothermic Reaction with a Catalyst This is the same graph you sketched last time, so you can

just add the new catalyst activation energy.

Endothermic Reaction with Catalyst

Energy Diagrams1. Draw and label an energy diagram. Calculate the

activation energy and change in energy of the reaction• Reactants = 78.9 kJ• Products = 125.3 kJ• Activated complex = 300 kJ

• Reactants = 25.1 kJ• Products = 35.2 kJ• Activated complex = 49.0 kJ