Transcript Equilibrium Constants
Equilibrium Constants
Recall:
At equilibrium, the rate of the forward and reverse reactions are equal
The Equilibrium Constant, K
eq
For the reaction:
a
A +
b
B
c
C +
d
D At equilibrium: r fwd = r rev k fwd [A] a [B] b = k rev [C] c [D] d Sub in rate law equation Rearrange k fwd = [C] c [D] k rev [A] a [B] b d Sub in K eq for k fwd /k rev K eq = [C] c [D] d [A] a [B] b Equilibrium constant
Examples
Write the equilibrium constant expression for the following two reactions
a
) 2
NO
2 (
g
)
N
2
O
4 (
g
)
b
)
N
2 (
g
) 3
H
2 (
g
) 2
NH
3 (
g
)
Heterogeneous Equilibria
• Equilibrium systems can involve all states of matter • However, the concentration of a pure solid or liquid cannot change • Therefore, equilibrium constant expressions will not include solids and liquids
a
)
H
2
O
(
l
)
H
2
O
(
g
)
b
)
NH
4
Cl
(
s
)
NH
3 (
g
)
HCl
(
g
)
Magnitude of K
eq
K eq >> 1 K eq = [C] c [D] d [A] a [B] b At equilibrium there is more products than reactants. The reaction is
product favoured
K eq = 1 K eq << 1 At equilibrium there is an equal amount of products and reactants At equilibrium there is more reactants than products. The reaction is
reactant favoured
Example
Calculate the value of K eq
CO
2 (
g
)
H
2 (
g
) for the following system
CO
(
g
)
H
2
O
(
g
) At Equilibrium: [CO 2 ] = 0.0954 mol/L [H 2 ] = 0.0454 mol/L [CO] = [H 2 O] = 0.00460 mol/L
Practice
• P. 442-445 #1-6 • P. 448 #1-9