Bell RingerBell Ringer2NO(g) + O2(g) 2NO2(g) H = -27 kcal

Reaction Progress Reaction Progress

Reaction ProgressReaction Progress

Energy Energy

Energy Energy

A B

C D

Source: 2004 VA Chemistry EOC Exam

Which graph represents the reaction shown above?

Homework AnswersHomework Answers1. A, B

2. B

3. C

4. B

5. A

6. C

7. Inter

8. Intra

9. Dispersion forces

10. Boiling Point

11. Amorphous

12. Higher

13. Dipole-dipole

14. Freezing

15. Hydrogen bonding

16. 30ºC

17. 1.0 atm

18. 40ºC

19. 47ºC

20. 0.4 atm

Practice with EnthalpyPractice with EnthalpyCalculate H for the following reactions:

2 KBr (s) + I2 (g) 2 KI (s) + Br2 (l)

2 HCl (g) + 2 Ag 2 AgCl (s) + H2 (g)

Htotal = [2mol (-327.9 kJ/mol) + 1mol (0 kJ/mol)] -

[2mol (-393.8 kJ/mol) + 1mol (0 kJ/mol)]

Htotal = 131.8 kJ

Htotal = [2mol (-127.01 kJ/mol) + 1mol (0 kJ/mol)] -

[2mol (- 92.31kJ/mol) + 2mol (0 kJ/mol)]

Htotal = -69.40 kJ

ENDOTHERMIC

EXOTHERMIC

Entropy and Gibb’s Free EnergyEntropy and Gibb’s Free Energy

They work the same way!! “PRODUCTS – REACTANTS”

Stotal = Sproducts - Sreactants

Gtotal = Gproducts - Greactants

S > 0, entropy increases (more disorder)

S < 0, entropy decreases (less disorder)

G > 0, not spontaneous

G < 0, spontaneousG = 0, equilibrium

How do H, S, and G Relate?How do H, S, and G Relate?G = H - TS

Potassium bromide reacts with iodine at 345K. Will this reaction occur spontaneously?

2 KBr (s) + I2 (s) 2 KI (s) + Br2 (l)

Htotal = [2mol (-327.9 kJ/mol) + 1mol (0 kJ/mol)] -

[2mol (-393.8 kJ/mol) + 1mol (0 kJ/mol)]

Htotal = 131.8 kJ

Stotal = [2mol (106.3 J/mol K) + 1mol (152.21 J/mol K)] -

[2mol(95.9 J/mol K) + 1mol (116.14 J/mol K)]

Stotal = 56.87 J/ K

112,000 J = 112 kJ

How do H, S, and G Relate?How do H, S, and G Relate?G = H - TS

Potassium bromide reacts with iodine at 345K. Will this reaction occur spontaneously?

2 KBr (s) + I2 (s) 2 KI (s) + Br2 (l)

Htotal = 131.8 kJ

Stotal = 56.87 J/ K

G = 131,800 J – (345K)(56.87 J/K)

DG = 131800 J – 19620.15 J

G = 112179.85 J

NOT SPONTANEOUS!

x1 kJ

1000 J= 131,800 J

Properties of WaterProperties of Water

Ms. BesalMs. Besal

3/24-27/20063/24-27/2006

Characteristics of WaterCharacteristics of Water• Bent ShapeBent Shape• Hydrogen BondingHydrogen Bonding• Liquid at Room TemperatureLiquid at Room Temperature• Requires great amount of energy to Requires great amount of energy to

change (raise or lower) temperaturechange (raise or lower) temperature• Expands as a solidExpands as a solid• High boiling pointHigh boiling point• High surface tensionHigh surface tension• High heat of vaporizationHigh heat of vaporization• ““universal” solventuniversal” solvent

OH

H

How does the flow of heat How does the flow of heat change water?change water?

0ºC

100ºC

A

SOLID

B

C

D

E

LIQUID

GAS

MELT

FREEZE

VAPORIZATION

CONDENSATION

TIME

TEM

P.

Hfus = 6.02 kJ/mol

Hvap = 40.7 kJ/mol

Phase Diagram of WaterPhase Diagram of Water

B

temperature

pre

ssu

re

A

C

D

solid liquid

gas.

FREEZE

MELT CONDENSATION

VAPORIZATION

SUBLIMATIONDEPOSITIO

N

Tc

E

B

temperature

pre

ssu

re

AC

D

solid liquid

gas.

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.

E