Chapter 11 Intermolecular Forces, Liquids, and Solids

1
Chapter 11Intermolecular Forces, Liquids, and
Solids
2
Of the following substances, predict which has
the highest boiling point based on intermolecular
forces.

• Propane, C3H8
• Dimethyl ether, CH3OCH3
• Methyl chloride, CH3Cl
• Acetaldehyde, CH3CHO
• Acetonitrile, CH3CN

3
Correct Answer

• Propane, C3H8
• Dimethyl ether, CH3OCH3
• Methyl chloride, CH3Cl
• Acetaldehyde, CH3CHO
• Acetonitrile, CH3CN

Each of these molecules has almost the same
molecular weight however, acetonitrile has the
largest dipole moment (3.9 D) and hence the
largest dipole-dipole forces. Thus it has the
highest boiling point.
4
Of the following substances, predict which has
the lowest boiling point based on London
dispersion forces.

• He
• Ne
• Ar
• Kr
• Xe

5
Correct Answer

• He
• Ne
• Ar
• Kr
• Xe

More massive species have more polarizability and
stronger London dispersion forces consequently,
amongst the noble gases He has the lowest boiling
point.
6
Of the following substances, predict which has
the highest boiling point based upon
intermolecular forces?

• CH4
• H2O
• H2S
• SiH4
• H2Se

N?H . OC
7
Correct Answer

• CH4
• H2O
• H2S
• SiH4
• H2Se

Of these, only H2O has any hydrogen bonding.
Hydrogen bonding substantially increases the
intermolecular forces, and hence the boiling
point.
8
Which one of the following phase changes is an
exothermic process?

• Sublimation
• Vaporization
• Condensation
• Melting

9
Correct Answer

• Sublimation
• Vaporization
• Condensation
• Melting

All the other phase-change processes listed are
endothermic.
10

• How much energy is required to raise the
  temperature of 1800. g ice at 0C to 10C? DHfus
  6.01 kJ/mol, heat capacity of water is 75.2
  J/mol-K.

• 60.1 kJ
• 75.2 kJ
• 135 kJ
• 601 kJ
• 676 kJ

11
Correct Answer
There are 100 moles of ice, so the enthalpy of
fusion is DH (6.01 kJ/mol)(100 mol) 601
kJ. To raise the water temperature 10C requires
q (75.2 J/mol-K)(100 mol)(10C ) 75.2 kJ.
Total energy 601 kJ 75 kJ 676 kJ

• 60.1 kJ
• 75.2 kJ
• 135 kJ
• 601 kJ
• 676 kJ

12
In the unlabeled phase diagram below, the line
segment from A to B separates which two phases?

• Gas-liquid
• Liquid-solid
• Solid-gas

13
Correct Answer

• Gas-liquid
• Liquid-solid
• Solid-gas

14
Quartz is an example of which type of solid
crystalline or amorphous?

• Crystalline
• Amorphous

15
Correct Answer
In quartz, the Si?O bonds are arranged in
regular, defined arrays.

• Crystalline
• Amorphous

16

• What are the net number of Na and Cl? ions in
  the NaCl unit cell represented below?

• 4 Na, 4 Cl?
• 2 Na, 1 Cl?
• 2 Na, 2 Cl?
• 1 Na, 2 Cl?
• 1 Na, 1 Cl?

17
Correct Answer
There are 4 Na resulting from (1/4
Na/edge)(12 edges) 3 Na (1 Na/center)(1
center) 1 Na There are 4 Cl- resulting from
(1/8 Cl?/corner)(8 corners) 1 Cl? (1/2
Cl?/face)(6 faces) 3 Cl?

• 4 Na, 4 Cl?
• 2 Na, 1 Cl?
• 2 Na, 2 Cl?
• 1 Na, 2 Cl?
• 1 Na, 1 Cl?

18

• The NaCl crystal shown below is an example of
  which type of cubic lattice?

• Primitive cubic
• Body-centered cubic
• Face-centered cubic

19
Correct Answer

• Primitive cubic
• Body-centered cubic
• Face-centered cubic

NaCl is an example of a face-centered crystalline
lattice.
20

• Diamond and graphite are examples of which type
  of crystalline solids?

• Molecular
• Covalent network
• Ionic
• Metallic

21
Correct Answer

• Molecular
• Covalent network
• Ionic
• Metallic

Diamond and graphite are both forms of carbon,
and consist of a network of covalent bonds (hence
covalent network).