1. Chemical Equilibrium

2. Reversible Chemical Reaction
A chemical reaction in which the products can regenerate the original reactants.

3. Forward Reaction:
Reactants
Products
Reverse Reaction:
Reactants
Products

4. Reactants
Products
The two half-arrows show that the reaction can proceed in either direction.
The two reactions
are opposite processes.

5. Reversible Chemical Reactions
                                                                                       
2NO2(g)
N2O4(g)

6. Water Cycle … Reversible Reactions

7. Reversible Chemical Reactions

8. CHEMICAL EQUILIBRIUM
The rate of the forward reaction is equal to the rate of the reverse reaction.

9. CHEMICAL EQUILIBRIUM
At Equilibrium concentrations of products and reactants remain constant.

10. CHEMICAL EQUILIBRIUM
The reaction does not stop when it reaches equilibrium!
Dynamic
Equilibrium!

11. [ ] CHEMICAL EQUILIBRIUM
Concentrations are expressed by the use of brackets.
[ ]
Moles
Molarity =
Liter

12. THE EQUILIBRIUM CONSTANT (keq)
A ratio of the concentrations of the products over the concentrations of the reactants.
cC + dD
aA + bB
[ C ] c
[ D ] d
Keq =
[ A ] a
[ B ] b

13. THE EQUILIBRIUM EXPRESSION
aA + bB
cC + dD
Raised to the power of the coefficient
PRODUCTS
Keq =
[ C ] c
[ D ] d
[ A ] a
[ B ] b
REACTANTS
Concentrations in Moles per Liter

14. THE EQUILIBRIUM EXPRESSION
ALWAYS WRITE PRODUCTS OVER REACTANTS.
NEVER INCLUDE SOLIDS OR LIQUIDS IN THE EXPRESSIONS

15. [H20] Keq = [H2] [O2] Practice Problem #1 2 2
Write the equilibrium expression for the oxidation of hydrogen to form water vapor. (homogeneous equilibrium)
2H2(g) + O2(g)
2H2O (g)
[H20] 2
Keq =
[H2]
[O2] 2

16. [CO2] Keq = [CO] *Practice Problem #10 2 2
Write the equilibrium expression for the following reaction. (heterogeneous equilibrium)
SnO2(s) + 2CO(g)
Sn(s) + 2CO2(g)
[CO2] 2
Keq =
[CO] 2

17. LAW OF CHEMICAL EQUILIBRIUM
Every reversible reaction will move to the state of equilibrium where there is a specific ratio of products and reactants.

18. EQUILIBRIUM CONSTANT (Keq)
Indicates the extent to which a reaction proceeds to completion
“significantly greater than”
If Keq > 1, equilibrium lies to the right.
Favors the products!
If Keq < 1, equilibrium lies to the left.
Favors reactants, reaction barely even starts!

19. EQUILIBRIUM CONSTANT (Keq)

20. “approximately equal to”
If Keq  1, you would find considerable concentrations of both reactants and products.

21. Q tells which direction the reaction will shift to reach equilibrium.
REACTION QUOTIENT (Q)
Q tells which direction the reaction
will shift to reach equilibrium.
Q is calculated the same
way that Keq is;
however the concentrations
are measured at any point
during the reaction.

22. Q < Keq What If . . . Reactant concentrations too LARGE
Product concentrations too SMALL
Reaction will proceed to the RIGHT

23. Q > Keq What If . . . Product concentrations too LARGE
Reactant concentrations too SMALL
Reaction will proceed to the LEFT

24. No shift in direction will occur.
What If . . .
Q = Keq
The reaction is at equilibrium.
No shift in direction will occur.

25. Practice Problem #20 For the reaction H2(g) + CO2(g) CO(g) + H2O(g)
Keq = 5.10 at 527ºC.
If [CO] = 0.15M, [H2O] = 0.25M,
[H2] = 0.42M, and [CO2] = 0.37M, calculate Q and determine how the reaction will proceed.

26. [CO2] [H2] Q = [CO] [H2O] [0.37] [0.42] Q = [0.15] [0.25]
Practice Problem #20
CO(g) + H2O(g)
H2(g) + CO2(g)
[CO2] [H2]
Q =
[CO] [H2O]
[0.37] [0.42]
Q = =
[0.15] [0.25]

27. The reaction will proceed direction of the products.
Practice Problem #20
CO(g) + H2O(g)
H2(g) + CO2(g)
Q = 4.144
Compare Q to Keq
Keq = 5.10
The reaction will proceed
to the right in the
direction of the products.
Q < Keq