1. EQUILIBRIUM

2. How Do Chemical Reactions Really Occur?
Can you put 2 chemicals together and they spontaneous react?
Let’s try it!

3. What’s really happening…
Molecules react by colliding into each other. There must be a minimum amount of energy available for the reaction to occur, it’s called ACTIVATION ENERGY!
If the collision is violent enough (has enough ENERGY) then bonds are broken and remade.
This is called a SPONTANEOUS REACTION!
If there is NOT enough energy, and we have to add some, we say the reaction is NONSPONTANEOUS.
We add energy in the form of heat, light, or electricity!

4. Activation Energy

5. Reaction Rates & What Affects Them
Reaction Rate- how fast the reaction goes from reactants to products.
What can change the rate of a reaction?

6. CW- Equilibrium Section Review p 604 #1 - 7

7. Increasing the temperature speeds up the rate of a reaction!
WHY?
When the temperature increases, the speed of the molecules increases, the molecules move faster and hit each other harder (with more energy) which makes the reaction occur faster.
The reactants rise to that activation energy sooner!

8. Increasing the concentration of the reactants increases the rate too!
WHY?
This one is a no brainer….
The more molecules there are to collide, the more they will and the faster the activation energy threshold will be reached.

9. Adding a CATALYST will also increase the rate of a reaction!
WHY?
A catalyst is a substance that can speed up a reaction by its mere presence without being used up in the reaction.
It offers an alternative path for the reaction to proceed that has a lower activation energy.

10. Reversible Reactions We know that reactants form products
2H2 + O2 → 2H2O
Can we change the reaction around?
2H2O → 2H2 + O2
Yes, a lot of the time we can. We call it a reversible reaction
2H2 + O2 ↔ 2H2O

11. Equilibrium
By definition implies things are equal, or that there is a balance.
Chemists define EQUILIBRIUM as occurring when the rate of the forward reaction is equal to the rate of the reverse reaction!

12. HUH?????????
You have been lead, up to this point, that reactants proceed to completion
(until one of the reactants runs out- limiting reactant)
Some reactions do work this way BUT…
Some reactions stop short of that goal! Why?
Because the reverse reaction is happening

13. 2NO2(g) ↔ N2O4(g)
NO2 is a reddish-brown gas
N2O4 is a clear gas

14. LeChatelier’s Principle
When a change is imposed on a system at equilibrium, the position of the equilibrium shifts in a direction that tends to reduce the effect of that change.

15. N2(g) + 3H2(g) ↔ 2NH3(g) Where would the equilibrium shift if you…
Increase the concentration of N2?
Increase the concentration of NH3?
Reduce the concentration of H2?

16. CaCO3(s) ↔ CaO(s) + CO2(g)
What is the effect of…
Decreasing the volume of the container?
Increasing the volume of the container?

17. N2(g) + 3H2(g) ↔ 2NH3(g) + 92kJ EXOTHERMIC reaction- gives off heat
What happens when you…
Increase the temperature?
Decrease the temperature?

18. CaCO3(s) + 556 kJ↔ CaO(s) + CO2(g)
ENDOTHERMIC reaction- absorbs energy
What happens when you…
Increase temperature?
Decrease temperature?