The Foundations of Chemistry

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,

H
EP
V (constant Tand P)

From Section 15-10, we know that 
Eqw,so

HqwP
V (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)