KEY
Homework
Chapter 11: Intermolecular Forces, Liquids, and Solids
Exercises: Sections 11.8: Bonding in Solids
1. What type of attractive forces exist between particles in:
(a) molecular crystals
 London dispersion forces
 dipole-dipole
 hydrogen-bonding
(b) covalent-network crystals
 covalent bonds
(c) ionic crystals
 ion-ion attraction (electrostatic attraction)
(d) metallic crystals
sea of electrons (metallic bonding)
2. Indicate the type of crystal (molecular, metallic, covalent-network, or ionic) each of the following would form upon solidification:
metallic
(a) Zr
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(b) N2O4
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(c) Si
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(d) Ne
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(e) Ni(ClO3)2
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(f) para-dichlorobenzene (moth balls).
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(g) ZrO2 (mp = 2677oC)
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(h) benzene
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(i) CaCO3
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molecular
covalent-network
molecular
ionic
molecular
ionic
molecular
ionic
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3. Covalent bonding occurs in both molecular and covalent-network solids. Why do these two kinds of solids differ so greatly in
their hardness and melting points?
Molecular
Solids
Covalent
Network
Crystal
=
individual molecules held together by
relatively weak IMF
=
no individual molecules, all atoms are covalently
bonded to one another to make a large network
crystal
4. Which type (or types) of crystalline solid is characterized by each of the following:
(a) high mobility of electrons throughout the solid;
metallic
(b) softness, relatively low melting point; molecular
(c) high melting point and poor electrical conductivity;
(d) charged particles throughout the solid;
covalent-network or ionic
ionic
5. You are given a white substance that sublimes at 3000oC; the solid is a nonconductor of electricity and is insoluble in water.
Which type of solid (Table 11.7 on page 464 of the textbook) might this substance be?




NOT metallic b/c not a conductor
NOT molecular b/c very high melting point
probably NOT ionic b/c it's not soluble
MOST LIKELY covalent-network
8. For each of the following compounds, predict which will have the higher melting point and indicate why?
(a) NaF, MgF2;
2+
b/c Mg vs Na+ ; stronger attraction between ions
(b) HF, HCl;
HF = has H-bonding as additional IMF to overcome
b/c
HCll = does NOT have H-bonding
(c) C (graphite), CO;
b/c C is a covalent-network crystal w/ covalent bonds; CO = only weak IMFs
(d) Kr, Ar.
b/c its larger molar mass means stronger London dispersion forces
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