2A
2B + C
2A
0.014
0.014
B
0.012
0.012
0.010
[ ] (M)
0.010
[ ] (M)
2B + C
0.008
C
0.006
0.004
B
0.008
0.006
C
A
0.004
0.002
0.002
A
0.000
0
1000
2000
3000
4000
0.000
5000
0
1000
2000
Time (s)
CO(g) + 2 H2(g)
[H2]i
[CH3OH]i
[CO]eq
[H2]eq
[CH3OH]eq
1
1.000
1.000
0.000
0.911
0.822
0.089
2
0.000
0.000
1.000
0.753
1.506
0.247
3
1.000
1.000
1.000
1.380
1.760
0.620
0.5
[ ] (M)
1.5
1.0
1.0
0.5
0.0
100
200
300
400
5000
aA + bB
rate law:
cC + dD
equilibrium constant expression:
[C]c[D]d
1.5
rate = k[A]x[B]y
1.0
experimentally (x, y)
balanced equation (a, b, c, d)
gas, solution
gas, solution
k experimentally
K value experimentally
(Kc)
K =
[A]a[B]b
0.5
0.0
0
4000
Kinetics versus Equilibrium
[CO]i
[ ] (M)
[ ] (M)
CH3OH(g)
Exp
1.5
3000
Time (s)
0.0
0
100
Time (s)
200
300
400
0
100
200
Time (s)
300
400
Time (s)
[X]eq depends on [X]i
As Written
Predicting the Direction of a Reaction
aA + bB
cC + dD
Can write equilibrium constant expression for any reaction,
K >> 1: [P] > [R] favors P
but numerical value (K) depends on:
qualitative
1. direction reaction is written
2. balancing coefficients
3. concentrations as [X] or PX
A
B
2A
A(g)
K << 1: [R] > [P] favors R
B
A
2B
careful with stoichiometry; Kp / K
B(g)
quantitative reaction quotient: Q like K , [X]i not [X]eq
expression (with value) applies to reaction: as written
Q =
[C]ci [D]di
[A]ai [B]bi
> K
toward R
< K
toward P
= K at equilibrium
1
Equilibrium Table
Equilibrium Table
2 HOCl(g)
sulfur trioxide decomposes at 1000 K:
flask filled with SO3 to 0.00609 M; heated to 1000 K
at equilibrium, [SO3] is found to be 0.00244 M; calculate
Calculate K
K.
2 SO3(g)
initial
change (Δ)
2 SO2(g)
+
O2(g)
[SO3]
[SO2]
[O2]
0.00609
0
0
K =
+
H2O(g)
[Cl2O]
[H2O]
1.00
0
1.00
initial
change (Δ)
equilibrium
Q =
K =
equilibrium
Cl2O(g)
[HOCl]
[Cl2O]i[H2O]i
[HOCl]i2
[Cl2O][H2O]
(0)(1.00)
=
(1.00)2
= 0
[HOCl]2
[SO2]2[O2]
[SO3]2
2