1. Equilibrium L

2. Remember this?
Collision theory: reactants only react when they collide at the correct angle and with sufficient energy to do so.
Once they collide correctly and with enough energy they form an activation complex (unstable)
transition state – physical arrangement of particles during the activation complex
How much energy they require is the activation energy
Types of collisions
Fruitful – forms a product

3. Reaction rates Fast rxn (More collisions) = less time, faster rate
Slow rxn (Less collisions) = more time, slower rate

4. Slower vs Faster Change the mechanism Change the temperature
Add steps to the process (inhibitor)
Remove steps (catalyst)
Change the temperature
Change concentration
Pressure (gases)
Less volume to move in, higher concentration
Surface area (solids)
Particle size controls how face a reaction happens

5. Equilibrium State of rate balance between two opposing changes Ex:
Escalader
Treadmill
Haircuts
Nails
Money
3 types

6. Reaction equilibrium
Rate of Synthesis = Rate of decomposition +

7. Solution equilibrium Saturated solution
Rate of dissolving = rate of precipitation

8. Phase equilibrium Rate of melting = rate of freezing
Rate of vaporization = rate of condensation
Rate of sublimation = rate of deposition

9. Changing equilibrium
Anything that will change the reaction rate will shift the equilibrium
Types of reactants
More reactive = faster reaction
Concentrations
Increased reagents = more chances for collisions
Surface area
Increased exposure to reagents
Temperature
Increased kinetic energy
Addition of a catalyst
Decreases activation energy

10. Properties of equilibrium
Closed system = no change in anything that would affect equilibrium
A system at equilibrium will stay that way forever unless some property of the system changes
Dynamic – ALWAYS in motion

11. H2O(l) H2O(g)

12. So what… Equilibrium is about RATES, not concentration
At equilibrium the concentration of products does NOT have to equal the concentration of reactants
[p] ≠ [r]
Keq = measures how far a reaction gets
Equilibrium constant
Ratio of products to reactants
Can be calculated by setting up a
mass action expression
Keq =[p]/[r]

13. Mass action expression
Keq =[p]/[r]
+ = multiply
Coefficients = exponents
Use brackets to signal molar concentration
Ex:
2CO2 2CO(g) + O2(g)

15. Practice N2O4(g)  2NO2(g) 2H2S(g)  2H2(g) + S2(g)
CO(g) + 3H2(g)  CH4(g) + H2O(g)
2H2S(g)  2H2(g) + S2(g)

16. Solving for Keq Keq = 1 Simply plug and chug
Find the equilibrium constant for the decomposition of 4M CO2, into 2M CO and 1M O2.
2CO2(g) 2CO(g) + O2(g)
Keq = 1

17. Practice Calculate Keq given: N2O4(g)  2NO2(g)
CO(g) + 3H2(g)  CH4(g) + H2O(g)
Substance
Concentration
N2O4
0.0613M
NO2
0.0627M CO H2
0.1839M
CH4
0.0387M
H2O

18. Quick note on Keq
Till now we’ve only looked at Homogenous equilibria (all one phase)
Since concentration is density (Mol/L) in solids or liquids the density of a PURE substance doesn’t change it remains constant and can be negated
In a heterogenous equilibrium (mixed phase) write only substances in the gas phase.
I2(s)  I2(g)
Keq = [I2(g)]

19. Practice C10H8(s)  C10H8(g) CaCO3(s)  CaO(s) + CO2(g)
C(s) + H(g)O(g)  CO(g) + H2(g)

20. LE CHATELIER’S PRINCIPLE
Life is a see-saw
If stress is applied to a system at equilibrium, the system will shift to relieve that stress
Stress = Change in temperature, concentration, volume or pressure
Keq doesn’t change if concentration, volume or pressure changes

21. Changing Concentration
SYSTEM WILL ALWAYS SHIFT TO UNDO THE STRESS!
Adding reactants causes a shift towards the products
Removal of products, more products
Removing reactants shifts towards reactants

22. Changing Temperature Alters both Keq and equilibrium position
Since Heat can be thought of as either a product or a reactant (endo/exothermic)
Addition of heat will shift an endothermic reaction towards the products
Addition of heat will shift an exothermic reaction towards the reactants
Keq (equilibrium constant) increases in value when the temperature is lowered and decreases when the temperature is raised

23. Changing Volume/Pressure
Together because you can’t change volume without changing pressure
Only cause a shift if the number of moles of gaseous product is different then the total moles of gaseous reactants
Decreasing Volume/ increasing Pressure shifts gas reactions towards the side with fewer moles
Increasing Volume/ decreasing Pressure shifts gas reactions towards the side with more moles
If number of moles is equal on both sides the system cannot relieve the pressure

24. Making Le Chatelier work for you
More Product
More Reactant
Add reactant
Remove product
Change temperature
Change pressure
Add product
Remove reactant
Change temperature
Change pressure

25. AgCl + Heat <-->Ag+1 + Cl-1 3 things that would increase [AgCl]
Practice: Suppose you’re an evil scientist bent on world domination and to power your death ray you need a lot of silver chloride. What are 3 ways you could bend this reaction to your evil will, and then the WORLD!
Given:
AgCl + Heat <-->Ag+1 + Cl-1
3 things that would increase [AgCl]
Add Ag+1
Add Cl-1
Drop the temperature
Fire the LAZER!!!