Bell Ringer

1
Bell Ringer
2NO(g) O2(g)
2NO2(g) DH -27 kcal
Which graph represents the reaction shown above?
A
B
Energy
Energy
Reaction Progress
Reaction Progress
C
D
Energy
Energy
Reaction Progress
Reaction Progress
Source 2004 VA Chemistry EOC Exam
2
Homework Answers

1. A, B
2. B
3. C
4. B
5. A
6. C
7. Inter
8. Intra
9. Dispersion forces
10. Boiling Point

1. Amorphous
2. Higher
3. Dipole-dipole
4. Freezing
5. Hydrogen bonding
6. 30ºC
7. 1.0 atm
8. 40ºC
9. 47ºC
10. 0.4 atm

3
Practice with Enthalpy
Calculate DH for the following reactions
2 KBr (s) I2 (g)
2 KI (s) Br2 (l)
DHtotal
2mol (-327.9 kJ/mol) 1mol (0 kJ/mol) -
2mol (-393.8 kJ/mol) 1mol (0 kJ/mol)
DHtotal 131.8 kJ
ENDOTHERMIC
2 HCl (g) 2 Ag
2 AgCl (s) H2 (g)
DHtotal
2mol (-127.01 kJ/mol) 1mol (0 kJ/mol) -
2mol (- 92.31kJ/mol) 2mol (0 kJ/mol)
DHtotal -69.40 kJ
EXOTHERMIC
4
Entropy and Gibbs Free Energy
They work the same way!! PRODUCTS REACTANTS
DStotal DSproducts - DSreactants
at 298 K!
DS gt 0, entropy increases (more disorder)
DS lt 0, entropy decreases (less disorder)
DGtotal DGproducts - DGreactants
at 298 K!
DG gt 0, not spontaneous
DG lt 0, spontaneous
DG 0, equilibrium
5
How do H, S, and G Relate?
not at 298 K!
DG DH - TDS
Potassium bromide reacts with iodine at 345K.
Will this reaction occur spontaneously?
2 KBr (s) I2 (s)
2 KI (s) Br2 (l)
DHtotal
2mol (-327.9 kJ/mol) 1mol (0 kJ/mol) -
2mol (-393.8 kJ/mol) 1mol (0 kJ/mol)
DHtotal 131.8 kJ
DStotal
2mol (106.3 J/mol K) 1mol (152.21 J/mol K) -
2mol(95.9 J/mol K) 1mol (116.14 J/mol K)
DStotal 56.87 J/ K
6
How do H, S, and G Relate?
DG DH - TDS
Potassium bromide reacts with iodine at 345K.
Will this reaction occur spontaneously?
2 KBr (s) I2 (s)
2 KI (s) Br2 (l)
DHtotal 131.8 kJ

131,800 J
DStotal 56.87 J/ K
DG 131,800 J (345K)(56.87 J/K)
DG 131800 J 19620.15 J
112,000 J 112 kJ
DG 112179.85 J
NOT SPONTANEOUS!
7
Properties of Water

• Ms. Besal
• 3/24-27/2006

8
Characteristics of Water

• Bent Shape
• Hydrogen Bonding
• Liquid at Room Temperature
• Requires great amount of energy to change (raise
  or lower) temperature
• Expands as a solid
• High boiling point
• High surface tension
• High heat of vaporization
• universal solvent

O
H
H
9
How does the flow of heat change water?
E
GAS
VAPORIZATION
DHvap 40.7 kJ/mol
100ºC
D
CONDENSATION
C
TEMP.
LIQUID
MELT
0ºC
B
DHfus 6.02 kJ/mol
A
FREEZE
SOLID
TIME
10
Phase Diagram of Water
E
B
FREEZE
C
liquid
pressure
solid
CONDENSATION
MELT
VAPORIZATION
.
A
gas
D
SUBLIMATION
DEPOSITION
Tc
temperature
11
E
B
liquid
solid
C
.
pressure
A
D
gas
temperature
A Triple point the temperature and pressure at
which gas, liquid, and solid form of a substance
all exist in equilibrium. B Melting curve C
Vaporization curve D Sublimation curve E
Critical point the temperature and pressure
above which gas cannot be liquefied no matter how
much pressure is applied.