Kinetics & Equilibrium
Dr. Ron Rusay
Spring 2004
© Copyright 2004 R.J. Rusay
Dynamic Equilibrium
“The Pennies”
• Organize into groups of 3-4.
• Dr. R will assign your group a number.
• In your group, select one person as:
1) Money Keeper
2) Recorder
3) Transfer Agent (Calculating agent)
4) Auditor (Can be combined with #3)
• Send the Recorder to see Dr. R. for your accounting form.
Be sure to record other group member names on the form.
• After recording all of the names send the Money Keeper
to see Dr. R. for your capital stake.
• Await instructions for phase I.
Dynamic Equilibrium
“The Pennies”
Phase I:
Phase II:
There will be 8 phases. You can begin and go through them at your own pace.
Give Dr. R. the accounting form when completed.
Pennies Results
Group
Rate
ini tial
ch ange
fin al
ini tial
ch ange
fin al
IA
-50%
40
-10%
0
IIA
-25%
20
IIB
-50%
20
IIIA
-10%
20
IIIB
-50%
20
IVA
-50%
0
IVB
-25%
40
20
-50%
20
-10%
25
-25%
15
-50%
28
-10%
12
-50%
10
-50%
30
-25%
12
-50%
28
-10%
20
-25%
13
-50%
31
-10%
9
-50%
12
-50%
28
-25%
9
31
-10%
27
-25%
14
-50%
33
-10%
7
-50%
13
-50%
27
-25%
33
27
14
34
6
13
27
ini tial
ch ange
fin al
-50%
ini tial
ch ange
fin al
ini tial
ch ange
fin al
ini tial
ch ange
fin al
ini tial
ch ange
fin al
ini tial
ch ange
fin al
IB
7
-25%
-50%
-50%
-10%
-50%
-25%
-10%
-50%
22
-25%
18
-50%
14
-50%
26
-10%
19
-50%
21
-25%
25
-10%
15
-50%
25
-25%
15
-50%
10
-50%
30
-10%
14
-50%
26
-25%
30
-10%
10
-50%
27
-25%
13
-50%
8
-50%
32
-10%
14
-50%
26
-25%
32
-10%
-50%
27
13
33
14
26
33
7
7
7
Dynamic Equilibrium
“The Pennies”
Simulator:
http://mc2.CChem.Berkeley.EDU/Java/equilibrium/
Class Results
http://ep.llnl.gov/msds/chem120/equil-graph.html
Dynamic Equilibrium
“The Pennies”
http://ep.llnl.gov/msds/chem120/equil-graph.html
Chemical Equilibrium
QuickTime™ and a
Intel Indeo® Video R3.2 decompressor
are needed to see this picture.
Reaction Diagram of O3 decomposing
Chemical Equilibrium
 Most of the reactions considered until now
have had reactants react completely to form
products. These reactions “went” only in one
direction. []
 Some reactions can react in either direction.
They are “reversible”. [
]When this occurs
some amount of reactant(s) will always
remain at the end of change. Weak acids and
bases follow this type.
Chemical Equilibrium
(Definitions)
A chemical system where the
concentrations of reactants and
products remain constant over time.
 On the molecular level, the system is
dynamic: The rate of change is the
same in both the forward and reverse
directions.

Law of Mass Action
(The Equilibrium Expression)
 For
a reaction:
• jA + kB
lC + mD
 The law of mass action is represented
by the Equilibrium Expression: where K
is the Equilibrium Constant. (Units for K
will vary.)
l
C D
K
j
A B
m
k
Equilibrium Expression


4 NH3(g) + 7 O2(g)  4 NO2(g) + 6 H2O(g)
The following Equilibrium Expression can have the
amounts uniformly expressed as units of
concentration mol/L (M), or as units of pressure
(atm).
4
6
NO2 H 2O
K
4
7
NH3 O2
Equilibrium Expressions
If
a reaction is re-written where the
reactants become products and
products-reactants, the new Equilibrium
Expression is the reciprocal of the old.
Knew = 1/Koriginal
When the entire equation for a reaction
is multiplied by a molar factor n,
Knew = (Koriginal)n
Le Châtelier’s Principle
.
. . If change is imposed on a
system at equilibrium, the
position of the equilibrium will
shift in a direction that tends to
reduce that change.
Le Châtelier’s Principle
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
Changes on the System

Concentration: The system will shift
concentrations away from the added
component. K remains the same.
Changes on the System (continued)
The Effect of Catalysts
A
catalyst lowers the activation energy
barrier for any reaction….in both
forward and reverse directions!
 A catalyst will decrease the time it takes
to reach equilibrium.
 A catalyst does not effect the
composition of the equilibrium mixture.
Reaction Diagram of O3 decomposing
Catalysts Lower the Energy of Activation
with Freon
O3
O2
Electromagnetic Radiation:
Light, Energy, Sunburn
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Ozone, sunscreen and SPF.
http://chemistry.beloit.edu/Stars/EMSpectrum/index.html
Catalytic Destruction of Ozone
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
Satellite Images of the
Antarctic Ozone Hole