Chemistry 12 - Reaction Kinetics

Reaction Rate

How fast the amount of reactant or product changes

Δ amount / Δ time

Describe ways to monitor reaction rates in an open system

1. Change in mass of gas

2. Temperature change *

3. Concentration change of coloured ions

4. Change in pH

Describe ways to monitor reaction rates in a closed system

1. Temperature change

2. Change in pressure

3. Change in volume

4. Concentration of coloured ions changes

5. Change in pH

Ways to measure reaction rates

Average rate (overall rate in specific time frame ex: 5s-25s)

Instantaneous Rate (rate at a specific moment in time ex: 10.00s)

What are factors that affect reaction rates?

• Surface area (increasing Surface Area makes reaction rate increase)

• —> only affects solids in heterogeneous rxn

• Temperature

• —> affects all rxns

• Pressure

• —> only affects rxns with gaseous reactants

• Phase

• —> think mobility, proximity, attraction

• Nature of Reactants

• —> strength of bonds, # of bonds

Describe collision theory & effective collisions

For a rxn to occur, molecules must

• collide

• Have sufficient KE

• Have correct molecular geometry when colliding

Explain energy changes in chemical reactions

• Endothermic reactions have more potential energy

• Exothermic reactions have more kinetic energy

How can you measure the ΔH

Distance from reactants to products

What does a catalyst do?

Speeds up a rxn without getting used up

Rate Determining Step

Slowest reaction/ equation

Reaction Intermediates

Produced + used up in a reaction

(Cancels out in equation)

Activated Complex

Highest Potential Energy in whole reaction