1. Kinetics and Equlibrium
Reaction rates and Reversible reactions

2. Kinetics - Collision Theory
Molecules react by colliding with each other with enough energy and proper orientation to break bonds, rearrange and form new bonds
Explains why increasing concentration of reactants (solutions) increases rate of reaction (more particles collide)
Explains why increasing temperature increases reaction rate (increases the energy (speed)) of the particles

3. Activation Energy

4. Equilibrium Reversible Reactions
When reactants come together the forward reaction starts.
Since there are no products there is (initially) no reverse reaction.
As the forward reaction proceeds the reactants are used up so the forward reaction slows.
The products build up
If the reaction is reversible, the reverse reaction speeds up.

5. Equilibrium Reversible Reactions
Eventually a point is reached where the reverse reaction is going as fast as the forward reaction.
This is Chemical Equilibrium.
The rate of the forward reaction is equal to the rate of the reverse reaction.
The concentration of products and reactants stays the same, but the reactions are still running.

6. Equilibrium Reversible Reactions
Equilibrium position: the product and reactant concentrations at equilibrium.
Shown with the double arrow.
Products are favored
Reactants are favored
Catalysts speed up both the forward and reverse reactions but don’t affect equilibrium position.

7. LeChâtelier’s Principle
If a “stress” is applied to a system at equilibrium, the system will respond to relieve the “stress”.
Three types of stresses are applied.

8. Changing Concentration
If reactants are added (increasing their concentration).
The forward reaction will speed up.
More product will form.
Equilibrium “Shifts to the right”
Reactants ® Products
N H2 ↔ NH3 + heat

9. Changing Concentration
If products are added (increasing their concentration).
The reverse reaction will speed up.
More reactant will form.
Equilibrium “Shifts to the left”
Reactants ¬ Products
N H2 ↔ NH3 + heat

10. Changing Concentration
If products are removed (decreasing their concentration).
The forward reaction will speed up.
More product will form.
Equilibrium “Shifts to the right”
Reactants ® Products
N H2 ↔ NH3 + heat

11. Changing Concentration
If reactants are removed (decreasing their concentration).
The reverse reaction will speed up.
More reactant will form.
Equilibrium “Shifts to the left”.
Reactants ¬ Products
N H2 ↔ NH3 + heat

12. Changing Temperature N2 + 3 H2 ↔ 2 NH3 + heat
Reactions either absorb or release heat.
Endothermic reactions go faster at higher temperature.
Exothermic go faster at lower temperatures.
All reversible reactions will be exothermic in one direction and endothermic in the other direction.
N H2 ↔ NH3 + heat

13. Changing Temperature N2 + 3 H2 ↔ 2 NH3 + heat
As the temperature increases, the reaction proceeds in the endothermic direction.
As the temperature decreases, the reaction proceeds in the exothermic direction.
Reactants + heat ® Products (high T)
Reactants + heat ¬ Products (low T)
N H2 ↔ NH3 + heat

14. Changes in Pressure/Volume
As the pressure increases (or volume decreases), the reaction will shift in the direction of the least number of moles of gases.
At high pressure (low volume), reaction shifts to the right 2H2(g) + O2(g) ® 2 H2O(g)
At low pressure (high volume), reaction shifts to the left 2H2(g) + O2(g) ¬ 2 H2O(g)