Chemistry Reference
In-Depth Information
14.4 A. For 2 mol
C
3
H
8
:
(b) Equation I is the equation representing
¢
H
f
of
¢
H
6
¢
H
f
(CO)
8
¢
H
f
(H
2
O)
2
¢
H
f
(C
3
H
8
)
CO
2
,
and equation II represents
¢
H
f
of CO.
6(
110 kJ)
8(
286 kJ)
2(
105 kJ)
Therefore, for equation III,
273
8
kJ
¢
H
¢
H
f
(products)
¢
H
f
(reactants)
For 1 mol
C
3
H
8
:
273
8
kJ
2 mol C
3
H
8
gives the same value.
1 mol C
3
H
8
a
b
1370 kJ
B. (a) Reverse equation II and add:
393 kJ
(
110 kJ)
283 kJ
Self-Tutorial Problems
14.1
List the types of forces that hold particles of various
types of solids together, and give an example of a solid
that is held together by each type.
(b) Water is warmed
33.1°C
from
21.2°C.
(c) Water is warmed by
33.1°C
to
54.3°C.
(d) Water is warmed
33.1°C
to
54.3°C.
14.2
Explain how we know that gases at room temperature
are not composed of ions.
(e) Water is warmed
54.3°C
from
33.1°C.
(f) Water is changed from
33.1°C
to
21.2°C.
14.3
Which of the phases is characterized by having strong
intermolecular forces among molecules that (a) are per-
manently located in or near one site? (b) are not perma-
nently located in or near one site?
2.042 J/g
#
°C,
14.10
The specific heat of water vapor is
and that
4.184 J/g
#
°C.
of water is
The heat of vaporization of wa-
ter is 2260 J/g.
(a) Calculate the heat required to warm 16.9 g of water
from to
(b) Calculate the heat required to vaporize the water.
(c) Calculate the heat required to warm the resulting
water vapor to
(d) Calculate the total heat required for all three processes.
14.11
What name can be given to the enthalpy change for each
of the following processes?
(a)
(b)
(c)
14.4
(a) What is the difference between condensation of a
gas to a liquid and vaporization of a liquid to a gas?
(b) Which process is endothermic?
(c) What is the difference between the heat of vaporiza-
tion and the heat of condensation?
87.4°C
100.0°C.
122.2°C.
14.5
(a) What is the difference between sublimation of a
solid and condensation of a gas to a solid?
(b) Which process is endothermic?
(c) What is the difference between the heat of sublima-
tion and the heat of condensation of a gas to a solid?
CO
2
(s) £ CO
2
(g)
H
2
O(
/
) £ H
2
O(g)
14.6
If 12.8 g of a metal at
74.2°C
is placed in 20.2 g of water
C(s)
O
2
(g) £ CO
2
(g)
(two answers)
at
26.2°C
and it warms the water to
31.7°C,
what is the
(d)
(e)
14.12
What types of calculations would we have to make to
find the energy required to change 14.8 g of ice at
to water vapor at
14.13
What characteristics should be chosen for a refrigerant
used to transfer heat from inside a refrigerator to outside
the refrigerator?
(a) High
C
3
H
4
(g)
4 O
2
(g) £ 3 CO
2
(g)
2 H
2
O(
/
)
final temperature of the metal?
3 C(s)
2 H
2
(g) £ C
3
H
4
(g)
14.7
If it takes 7.30 kJ of energy to warm 63.0 g of water from
to how much energy is required to cool
63.0 g of water from
18.2°C
45.9°C,
45.9°C
to
18.2°C?
15.0°C
119°C?
14.8
Calculate the final temperature if the initial temperature
of a system is
25.0°C
and the temperature change is
(a)
6.3°C
and (b)
6.3°C.
14.9
Identify the initial temperature, the final temperature, and
the change in temperature for each of the following cases:
(a) Water is warmed from
¢
H
vap
or low
¢
H
vap
?
(b) High molar mass or
low molar mass?
21.2°C
to 33.1°C.
Problems
14.1 Nature of the Solid and Liquid States
14.15
Which has the higher melting point—an ionic compound
in which the ions have single charges or an analogous
ionic compound in which each ion has a double charge?
14.14
Explain why solid LiF and solid
CF
4
melt at such widely
different temperatures:
870°C
and
184°C,
respectively.
