Quote of the day:
Willard Gibbs is, in my opinion, one of the
most original and important creative minds
in the field of science America has produced.
—Albert Einstein
Announcements
•If you don’t have a clicker with you, sign in after class
•Chapter 19 Homework- Finish it!
•Exam #1:
•This FRIDAY!
•Covers Chapter 5, 8.4, and 19 (through page 9-14)
•Study guide posted on course web site
Gibbs’ Free Energy
 Gibbs’ Free Energy:
G = H - TS
(All variables are in terms of the system)
 When G is negative, reaction is favored.
 When G is positive, reaction is disfavored.
 When calculating G, be careful with enthalpy units!
At 25°C, is this reaction spontaneous?
N2(g) + 3 H2(g)  2 NH3(g)
G = H - TS
2 Fe2O3(s) + 3 C(s)  4 Fe(s) + 3 CO2(g)
H = +468 kJ
What is G at 25 oC and at 1000 oC?
S = +561 J/K
Temperature Domains and Reaction Favorability
H
+
+
S
-
-
2 Fe2O3(s) + 3 C(s)  4 Fe(s) + 3 CO2(g)
H = +468 kJ
S = +561 J/K
In what temperature range will this reaction be
favored?
High or low?
What temperature?
At what temperature is this reaction spontaneous? (favored)
CaCO3(s)  CaO(s) + CO2(g)
H° = +178 kJ
S° = +161 J/K
25%
1.
2.
3.
4.
25%
25%
2
3
25%
High temperatures
Low temperatures
All temperatures
No temperatures
1
4
At what temperature is this reaction spontaneous? (favored)
C(s) + 2H2(g)  CH4 (g)
H° = -74.80 kJ
S° = -80.08 J/K
25%
1.
2.
3.
4.
25%
25%
2
3
25%
High temperatures
Low temperatures
All temperatures
No temperatures
1
4
At what temperatures is this reaction spontaneous? (favored)
N2(g) + 2O2(g)  2NO2(g)
H° = +66.36 kJ
S° = -121.77 J/K
25%
1.
2.
3.
4.
25%
25%
2
3
25%
High temperatures
Low temperatures
All temperatures
No temperatures
1
4
Free Energy vs. Temperature
Reaction 1 Reaction 2 Reaction 3
550
575
600
625
650
675
700
725
750
775
800
825
850
875
900
925
950
975
1000
1025
1050
1075
1100
1125
1150
1175
1200
1225
1250
468.00
0.56
G
159.45
145.43
131.40
117.38
103.35
89.33
75.30
61.28
47.25
33.23
19.20
5.17
-8.85
-22.88
-36.90
-50.93
-64.95
-78.98
-93.00
-107.03
-121.05
-135.08
-149.10
-163.13
-177.15
-191.18
-205.20
-219.23
-233.25
-80.08
0.07
G
G
-118.58
-120.33
-122.08
-123.83
-125.58
-127.33
-129.08
-130.83
-132.58
-134.33
-136.08
-137.83
-139.58
-141.33
-143.08
-144.83
-146.58
-148.33
-150.08
-151.83
-153.58
-155.33
-157.08
-158.83
-160.58
-162.33
-164.08
-165.83
-625
-0.65
G
-267.50
-251.25
-235.00
-218.75
-202.50
-186.25
-170.00
-153.75
-137.50
-121.25
-105.00
-88.75
-72.50
-56.25
-40.00
-23.75
-7.50
8.75
25.00
41.25
57.50
73.75
90.00
106.25
122.50
138.75
155.00
171.25
187.50
G as a Function of Temperature
Reaction 1
Reaction 2
Reaction 3
300.00
200.00
ΔG (kJ/mol)
H
S
T
100.00
0.00
-100.00
-200.00
-300.00
550
650
750
850
950
Temperature (°C)
1050
1150
1250
Free Energy of Formation: Only used at 25 oC
2 BaO(s) + C(s)  2 Ba(s) + CO2(g)
Exam #1 Review
Exam #1 Review
Exam #1 Review
Exam #1 Review
Chapter 11
Intermolecular Forces and the Liquid State
Review: Bonding
When atoms stick together, that’s bonding.
Why do Covalent Bonds Form?
Electrons on one
atom attracted to
nucleus of other
atom
Nucleus on each atom repels other nucleus
Electron on each atom repels other electron
If new attractions > new repulsions, then a bond forms
Determining Molecular Geometry
Valence
Electrons
Lewis
Structure
Electron-Pair Molecular
Geometry
Geometry
Chapter 11
Properties of Liquids and
Solids
Formula  Lewis Structure  Electron Geometry 
Molecular Geometry  Polarity 
Properties
Intermolecular Forces 
What happens when water boils. Draw pictures.
Bonding vs. Intermolecular Forces (IMFs):
Where do IMFs come from?
Types of forces between molecules: Intermolecular Forces (IMFs)
Ion-Dipole Forces: Between dissolved ions and polar molecules
Enthalpy of hydration:
Trends:
Dipole-Dipole Forces: Between polar molecules
Trends:
Dipole-Induced Dipole Forces: Between polar and nonpolar molecule
Trends:
Induced Dipole-Induced Dipole Forces: Between nonpolar molecules
Trends:
Hydrogen Bonding: Molecules with F-H, O-H, or N-H bonds
Hydrogen Bonding: Properties of water
Hydrogen Bonding: Properties of water
More on Boiling Points and Hydrogen Bonding
Identifying IMFs
Relative Contributions of Different IMFs
Properties of Liquids
• Vapor Pressure (volatility)
• Boiling Point
• Enthalpy of Vaporization
• Viscosity
• Surface Tension
Molecular interpretation of vapor pressure and boiling.
Enthalpy of vaporization:
Clausius-Clapyron Equation: Vapor Pressure, Hvap, and T
Graphical Method of Determining Enthalpy of Vaporization
Example 2.
What is the mass of water in the air in this lecture hall?
14 m x 5 m x 17 m
T = 22 oC
Humidity = 43%
Example 3.
A 1-L flask of air is at 30 oC and relative humidity of 68%. The flask is put
in a freezer and the temperature decreases to 5 oC. What happens?
Surface Tension