1. Equilibrium
Chemical Physical

2. Closed system Dynamic equilibrium
OUTCOME QUESTION(S):
C EQUILIBRIUM AND Keq
Relate the concept of equilibrium to physical and chemical systems.
Include: conditions necessary to achieve equilibrium.
Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.
Include: ICE tables
Vocabulary & Concepts
Closed system Dynamic equilibrium

3. FEW reactions end with NO reactants and 100% product
* Kinetics applies to the rate of a reaction.
2 Na (aq) + Cl2 (aq) NaCl (aq)
2 H2O (g) O2 (g) H2 (g)
FEW reactions end with NO reactants and 100% product
ex·tent (ikˈstent/):
the degree, size or scale of something.
In this case – how much product can be made?
Many products can collide and “reform” reactants: these reactions are called “reversible”
* Equilibrium applies to the extent of a reaction.

4. aA + bB cC + dD Concentration
Kinetic Region
Equilibrium Region
Consider the Collision Theory:
Can you explain why the concentrations plateau?
Reactants
Products
teqbm
Time

5. Which situation is likely to reach equilibrium? Why?
Equilibrium will only be reached with:
A reversible reaction
Sealed container
Constant condition ([ ], T, P, V)
closed system
H2O (l) H2O (g)
Which situation is likely to reach equilibrium? Why?
Physical equilibrium:
Reversible physical process, where rate of forward process is equal to rate of reverse process.

6. “Dynamic equilibrium”
Liquid – Vapour Physical Equilibrium:
Kinetic: molecules vapourize filling the space.
As more molecules vapourize, it becomes more likely for molecules to condense.
Equilibrium: evaporation rate = condensation rate.
Amounts of each stay constant (plateau)
VAPOUR
“Dynamic equilibrium”
changing balance
Macroscopically nothing appears to be changing BUT microscopically molecules are in flux.
LIQUID

7. Solubility equilibrium is only reached with a saturated solution
Solubility Physical Equilibrium:
Kinetic: molecules dissolve filling the space.
As more solute dissolves, it becomes more likely for molecules to precipitate.
Equilibrium: dissolving rate = precipitation rate.
Amounts of each stay constant (plateau)
SOLVENT
Solubility equilibrium is only reached with a saturated solution
C6H12O6(s) C6H12O6(aq)
SOLUTE

8. How is it different? How is it the same?
Other examples of physical equilibria include:
Vapour Pressure
Solid - Liquid (held at melting point)
Liquid - Vapour (held at boiling point)
The interaction of smog with the sun is an example of Chemical Equilibrium:
How is it different? How is it the same?
Photochemical smog
smog
2 NO2 (g) N2O4 (g)

9. 2 NO2 (g) N2O4 (g) Photochemical smog
Chemical Equilibrium:
Photochemical smog
smog
2 NO2 (g) N2O4 (g)
Kinetic: molecules convert to colourless variant.
As more molecules react, it becomes more likely for molecules of the reverse process to react.
Equilibrium: forward rate = reverse rate.
Concentrations of each stay constant (plateau)
The winter cold increases the conversion to colourless
(pollution looks less in winter – but it’s just invisible)

10. Constant macroscopic properties
Chemical equilibrium:
Reversible chemical process, where concentrations of reactants and products remain constant over time because the rates of the forward reaction equal the reverse reaction.
Constant macroscopic properties
At equilibrium (te):
Rate of forward reaction EQUALS rate of reverse reaction – indefinitely.
2. Concentrations of both reactants and products will be CONSTANT – not same, but constant.

11. aA + bB cC + dD Concentration Rate
Kinetic Region
Equilibrium Region
Kinetic Region
Equilibrium Region
Concentration
Rate
Reactants
Reactants
Products
Products
teqbm
teqbm
Time
Time
Notice that the time equilibrium is reached is the same for both graphs: the concentrations plateau because the forward and reverse rate are occurring at the same pace

12. Closed system Dynamic equilibrium
CAN YOU / HAVE YOU?
C EQUILIBRIUM AND Keq
Relate the concept of equilibrium to physical and chemical systems.
Include: conditions necessary to achieve equilibrium.
Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.
Include: ICE tables
Vocabulary & Concepts
Closed system Dynamic equilibrium