Chemistry Reference
In-Depth Information
(e)
van der Waals forces only
(f )
van der Waals forces only
13.49
and
(S and I have the same electronegativities, as do N and Cl.)
13.50 (a)
Angular
(b)
The angle in is less because the single electron does
not repel the other electron groups as well as the electron
pair in
13.51 (a)
Na 5058 kJ/mol Al 5140 kJ/mol
(b)
It takes less energy to produce
14.4
(a)
One is the reverse of the other. (See Figure 14.4.)
(b)
Vaporization is endothermic.
(c)
They have the same magnitude but opposite signs:
SI
2
NCl
3
Heat
vap
Heat
cond
14.6
When metal is placed in water, both the metal and the water
will finally come to the same temperature. The final temper-
ature of the metal is thus
NO
2
31.7°C.
NO
2
.
7.30 kJ.
14.7
It takes The same quantity of energy is involved,
but in the cooling process, the energy is
removed,
and its sign
is minus.
Na
2
(g) from Na(g) than
Al
3
it takes to form (g) from Al(g).
(c)
is the familiar ion in the solid state and in solution;
is not a stable species.
13.54 (a)
It is trigonal planar. (We know because the polar bonds
cancel.)
(b)
It is probably trigonal pyramidal.
13.56 (a)
Trigonal planar at each nitrogen atom
(b)
Nonlinear at each oxygen atom
13.59
For twice the distance,
14.8
(a)
31.3°C
(b)
18.7°C
Al
3
14.9
Initial (
C)
Final (
C)
Change (
C)
Na
2
(a)
21.2
33.1
11.9
(b)
21.2
54.3
33.1
(c)
21.2
54.3
33.1
(d)
21.2
54.3
33.1
(e)
33.1
87.4
54.3
(f )
33.1
21.2
11.9
d
2
2
d
1
:
14.10
(a)
Heat
mc
t
(16.9 g)(4.184 J/g·
C)(12.6
C)
890.
9
J
(b)
(c)
(2
d
1
)
2
4
d
1
2
f
2
k
k
f
1
4
Heat
m
¢
H
vap
(16.9 g) (2260 J/g)
38,1
9
0 J
Heat
mc
t
(16.9 g) (2.042 J/g·
C) (22.2
C)
766.
1
J
The force of attraction is reduced to one fourth.
For the larger distance,
(d)
Heat
890.
9
J
38,1
9
0 J
766.
1
J
39,800 J
39.8 kJ
10
9
m
3
14.11
(a)
Enthalpy of sublimation
(b)
Enthalpy of vaporization
(c)
10
10
m
15
2.0
(
15
)
2
225
The force is reduced to
or
times that in the lattice.
Enthalpy of formation of
CO
2
or of combustion of carbon
(d)
Enthalpy of combustion of
(e)
Enthalpy of formation of
C
3
H
4
22,400 cm
3
6.0
2
10
23
molecules
3.72
1
10
20
cm
3
13.61 (a)
C
3
H
4
14.12
We would do a specific heat calculation for the warming of
the ice to a heat of fusion calculation for the melting
of the ice, a specific heat calculation for the warming of the
water, a heat of vaporization calculation for the vaporization
of the water and another specific heat calculation for the
warming of the resulting water vapor. Finally, we would add
the five values together.
3
V
3.34
10
7
cm
3.34
10
9
m
(b)
2
0°C,
3.34
10
9
m
2.00
10
10
m
16.7
(c)
The molecules are on average about 16.7 times as far apart, so
their attraction would be
reduced
(16.7)
2
279
times to
1
279th of that in the solid.
14.13
(a)
High
¢
H
vap
(b)
Low molar mass
H
13.62
13.66
The line extends to about
14.14
LiF has strong bonds holding its ions together; has
only van der Waals forces holding its molecules to one
another.
CF
4
60°C,
160°C
below its real nor-
mal boiling point.
13.67
In water, there are two hydrogen atoms and two lone pairs in
each molecule, allowing for a three-dimensional hydrogen
bonded structure.
13.68
No pairs are as successful in hydrogen bonding as G-C and
A-T.
14.15
The compound with the doubly charged ions will melt at a
higher temperature. The stronger attractions of the dipositive
and dinegative charges require higher temperatures to dis-
rupt. For example, NaF melts at
993°C
and MgO melts at
2800°C.
14.18
SCl
4
(a molecular solid)
14 Solids and Liquids, Energies of Physical and
Chemical Changes
14.1
14.19
They have about the same van der Waals forces. Neither sub-
stance can exhibit hydrogen bonding because neither con-
tains hydrogen. ICl has a dipole and does not, so ICl
should have the greater intermolecular forces. Because it has
greater intermolecular forces, ICl boils at a higher tempera-
ture (ICl,
Forces
Example
Br
2
Chemical bonds
Ionic bonds
NaCl
97.4°C;
Br
2
,
58.78°C).
Covalent bonds
Diamond
Metallic bonds
Copper
14.21
The substance is a crystalline solid. The regularity of the po-
sitions of the particles is a characteristic of crystalline solids.
Intermolecular forces
van der Waals forces
Dipolar attractions
I
2
14.22
P
2
O
3
is a molecular solid;
Al
2
O
3
is an ionic solid.
ICl
14.23
HI has the greater molar mass and the greater number of
electrons. Therefore it has greater intermolecular forces, it
boils at a higher temperature (HI,
Hydrogen bonding
Ice
14.2
Gases have very small attractive forces between the particles
(Section 12.10). An ionic substance has strong ionic bonds be-
tween its ions. If an ionic substance were in the gaseous state at
room temperature, it would condense into a solid very quickly.
35.5°C,
HCl,
85°C).
14.27
(a)
The water boils.
(b)
The water warms up.
14.3
(a)
The solid phase
(b)
The liquid phase
14.30
There will be no change. Vapor pressure depends on temper-
ature, not surface area.
