The balanced chemical equation involves one mole of ethanol, so we can write the unit
factor
1m
1
o
m
l
o
e
l
th
rx
a
n
nol
. Then we express the result of Example 15-14 as
E
m
o
1
l
3
e
6
th
5
a
k
n
J
ol
1m
1
o
m
l
o
e
l
th
rx
a
n
nol
1365 kJ/mol rxn
RELATIONSHIP BETWEEN HAND E
The fundamental definition of enthalpy, H,is
HEPV
For a process at constant temperature and pressure,
HEPV (constant Tand P)
From Section 15-10, we know that Eqw,so
HqwPV (constant Tand P)
15-11
(a) This small piece of candy is
mostly sucrose, C 12 H 22 O 11 , a sugar.
(b) When the piece of candy is
heated together with potassium
chlorate, KClO 3 (a good oxidizing
agent), a highly product-favored
reaction occurs.
C 12 H 22 O 11 (s)12O 2 (g)88n
12CO 2 (g)11H 2 O(g)
If that amount of sucrose is
completely metabolized to carbon
dioxide and water vapor in your
body, the same amount of energy
is released, though more slowly.
618 CHAPTER 15: Chemical Thermodynamics
(a)
(b)