2H2O ? 2H2 O2

1

• 2H2O ? 2H2 O2
• H-O-H H-O-H ? H-H H-H OO

1836
4
459
872
2
436
498
1
498
1370
1836
466
2H2O 466 kJ ? 2H2 O2
2

• Forming a bond releases energy
• Breaking a bond requires energy
• The energy required to break a chemical bond the
  energy released when a bond is formed
• Endothermic
• Exothermic
• a) H-F (568 kJ/mol) b) O-O (145 kJ/mol)

436
1
436
243
1
243
864
2
432
864
679
185
H2 Cl2 ? 2HCl 185 kJ
3

• a) OO, H-O-H, OCO
• b) C25H52 38O2 ? 25CO2 26H2O
• c)

8352
24
348
21476
52
413
39950
50
799
23868
52
459
18924
38
498
63818
48752
15066
d) theoretical 15000 kJ, lab 7500 kJ The lab
value is about 50 of what it should have been
because the calorimeter was very inefficient
lots of heat energy was lost.
4

1. C2H5OH 3O2 ? 2CO2 3H2O

348
1
348
2065
5
413
360
1
360
2754
6
459
1
459
1494
3
498
3196
4
799
5950
4726
1224
C2H5OH 3O2 ? 2CO2 3H2O 1224 kJ Thus,molar
heat of combustion,?Hc1224 kJ/mol h 1224
kJ/mol x 1 mol/46.08 g 26.6 kJ/g
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