1. Approaching
Equilibrium
Lesson 1

2. Approaching Equilibrium
Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products

3. Approaching Equilibrium
Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Always on left Always on right 

4. Approaching Equilibrium
Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products

5. Approaching Equilibrium
Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Forward Rate is from
left to right

6. Approaching Equilibrium
Many chemical reactions are reversible if the activation energy is low.
Reactants ⇌ Products
Reverse Rate is from
right to left

7. Lets see what happens to some reactants if they are placed in a reaction vessel and allowed to react.

8. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

9. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

10. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

11. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

12. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

13. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

14. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate

15. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate
Are Equal

16. Approaching Equilibrium
Reactants
Products
Forward Rate
Reverse Rate
Are Equal
Are Constant

17. Time [Reactant] Forward Rate [Product] Reverse Rate Net Rate
15 

18. Equilibrium has been attained after 40 minutes
Equilibrium has been attained after 40 minutes. The forward and reverse rates are equal and the reactant and product concentrations are constant.

19. Graph the [reactant] and [product] as equilibrium is approached.
 Concentration
  8000
7000 
  6000
5000
  4000
3000
2000
1000
Time
equilibrium

20. Graph the forward, reverse, & net rates as equilibrium is approached.
  160
140 
  120
100
  80 60 40 20
Time
equilibrium

21. Approaching Equilibrium
Reactant concentrations start high and decrease as the reaction proceeds. The forward rate, which depends on collisions of the reactants, also decreases.
Product concentrations start at zero and increase as the reaction proceeds. The reverse rate, which depends on collisions of the products, also increases.
Eventually the forward rate is equal to the reverse rate and the concentrations are constant. This is equilibrium.

22. Characteristics of a System at Equilibrium
The Forward rate = The Reverse rate
The Reactant and Product concentrations are constant
The Macroscopic (observable) properties are constant
The system is Dynamic as the forward and reverse reactions continue.
The equilibrium can be approached from starting with reactants or starting with products.

23. Conditions Necessary for Equilibrium
The system is closed.
The temperature is constant.
The Ea is low enough so that the reaction is reversible.
Simulation1