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Chemistry for Engineering Students

Larry Brown, Tom Holme

Chapter 8

Molecules and Materials - all with Video Answers

Educators

Chapter Questions

00:27

Problem 1

How many solid forms of elemental carbon are known?

Lottie Adams
Lottie Adams
Numerade Educator
01:08

Problem 2

Why is the $\mathrm{C}_{60}$ form of carbon called buckminsterfullerene?

David Collins
David Collins
Numerade Educator
01:01

Problem 3

What property of diamond leads to the most engineering applications? Which types of applications would benefit from this property?

Narayan Hari
Narayan Hari
Numerade Educator
02:17

Problem 4

Which variables must be controlled and in what manner to produce diamonds from graphite?

Lottie Adams
Lottie Adams
Numerade Educator
01:08

Problem 5

What is the relationship between the structure of buckminsterfullerene and carbon nanotubes?

David Collins
David Collins
Numerade Educator
02:55

Problem 6

Use the web to look up information on nanotubes. Distinguish between single-walled and double-walled nanotubes.

Crystal Wang
Crystal Wang
Numerade Educator

Problem 7

Use the web to look up the experimental conditions required to synthesize buckminsterfullerene in an electric arc. Would running an arc in air work?

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01:43

Problem 8

What is the difference between an amorphous solid and a crystalline solid?

Ahmed Ali
Ahmed Ali
Numerade Educator
00:37

Problem 9

Define packing efficiency.

Ahmed Ali
Ahmed Ali
Numerade Educator
01:01

Problem 10

Using circles, draw regular two-dimensional arrangements that demonstrate low packing efficiency and high packing efficiency.

Carson Merrill
Carson Merrill
Numerade Educator
02:20

Problem 11

Using pentagons, draw arrangements that demonstrate low packing efficiency and higher packing efficiency.

Jay Patel
Jay Patel
Numerade Educator

Problem 12

Using circles, show that a cubic structure (squares in 2-D) has a lower coordination number than a hexagonal structure.

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03:33

Problem 13

Calculate the packing efficiencies for both two-dimensional arrangements shown in Figure 8.3.

Suzanne W.
Suzanne W.
Numerade Educator
03:16

Problem 14

Explain why hcp and ccp structures have the same coordination number.

Khalida Dawar
Khalida Dawar
Numerade Educator
01:49

Problem 15

What is the coordination number of atoms in the diamond structure?

Lottie Adams
Lottie Adams
Numerade Educator
01:56

Problem 16

Explain why graphite is described as having a layered structure.

Grigoriy Sereda
Grigoriy Sereda
Numerade Educator
03:25

Problem 17

Polonium is the only metal that forms a simple cubic crystal structure. Use the fact that the density of polonium is $9.32 \mathrm{~g} / \mathrm{cm}^3$ to calculate its atomic radius.

Freddie Montague
Freddie Montague
Numerade Educator
02:53

Problem 18

Iridium forms a face-centered cubic lattice, and an iridium atom is 271.4 pm in diameter. Calculate the density of iridium.

Eileen Sullivan
Eileen Sullivan
Numerade Educator
03:53

Problem 19

Europium forms a body-centered cubic unit cell and has a density of $4.68 \mathrm{~g} / \mathrm{cm}^3$. From this information, determine the length of the edge of the cubic cell.

Shalini Tyagi
Shalini Tyagi
Numerade Educator
02:14

Problem 20

Manganese has a body-centered cubic unit cell and has a density of $7.88 \mathrm{~g} / \mathrm{cm}^3$. From this information, determine the length of the edge of the cubic cell.

Adriano Chikande
Adriano Chikande
Numerade Educator
05:51

Problem 21

The spacing in a crystal lattice can be measured very accurately by X-ray diffraction, and this provides one way to determine Avogadro's number. One form of iron has a body-centered cubic lattice, and each side of the unit cell is 286.65 pm long. The density of this crystal at $25^{\circ} \mathrm{C}$ is $7.874 \mathrm{~g} / \mathrm{cm}^3$. Use these data to determine Avogadro's number.

Shazia Naz
Shazia Naz
Numerade Educator
04:15

Problem 22

How many electrons per atom are delocalized in the sea of electrons model for the following metals? (a) iron, (b) vanadium, (c) silver

Adriano Chikande
Adriano Chikande
Numerade Educator
03:02

Problem 23

One important physical property of metals is their malleability. How does the sea of electrons model account for this property?

Jennifer Hudspeth
Jennifer Hudspeth
Numerade Educator
01:04

Problem 24

The sea of electrons model is not generally used for quantitative predictions of properties. What factors are left out of this model that might prevent quantitative precision?

Jorge Villanueva
Jorge Villanueva
Numerade Educator
01:05

Problem 25

How does the sea of electrons model of metallic bonding explain why metals are good conductors of electricity?

Micah Hurewitz
Micah Hurewitz
Numerade Educator
01:35

Problem 26

What is the key difference between metallic bonding (in the sea of electrons model) and ionic bonding (as described in Chapter 7) that explains why metals conduct electricity and ionic solids do not?

David Collins
David Collins
Numerade Educator
02:43

Problem 27

What is the difference between a bonding orbital and an antibonding orbital?

Natalie Johns
Natalie Johns
Numerade Educator
01:52

Problem 28

Describe how the combination of atomic orbitals gives rise to bands in the limit of large numbers of atoms.

Chai Santi
Chai Santi
Numerade Educator
02:33

Problem 29

Draw a depiction of the band structure of a metal. Label the valence band and conduction band.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
01:49

Problem 30

How do conductors, insulators, and semiconductors differ according to band theory?

David Collins
David Collins
Numerade Educator
01:01

Problem 31

The conductivity of semiconductors increases as temperature is increased. Using band theory, explain this observation.

Jorge Villanueva
Jorge Villanueva
Numerade Educator
07:06

Problem 32

Use the web to find out what a "III-V" semiconductor is. How is this type of semiconductor related to silicon?

Susan Hallstrom
Susan Hallstrom
Numerade Educator
03:42

Problem 33

Explain how doping affects the electronic properties of a semiconductor.

Matthew Hurlock
Matthew Hurlock
Numerade Educator
01:30

Problem 34

What type of atom is needed as a dopant in an n-type semiconductor? Why is it called n-type?

Ajay Singhal
Ajay Singhal
Numerade Educator
01:37

Problem 35

What type of atom is needed as a dopant in a p-type semiconductor? Why is it called p-type?

Ajay Singhal
Ajay Singhal
Numerade Educator
01:30

Problem 36

Is an n-type semiconductor actually negatively charged?

Ajay Singhal
Ajay Singhal
Numerade Educator
01:20

Problem 37

How does a p-n junction serve as a voltage-gated switch?

Matthew Confer
Matthew Confer
Numerade Educator
03:04

Problem 38

Suppose that a device is using a $15.0-\mathrm{mg}$ sample of silicon that is doped with $1 \times 10^{-5} \%$ (by mass) phosphorus. How many phosphorus atoms are in the sample?

DW
David Walther
Numerade Educator
01:40

Problem 39

What is an instantaneous dipole?

Rachel Vallejo
Rachel Vallejo
Numerade Educator
View

Problem 40

Why are dispersion forces attractive?

Emily Himsel
Emily Himsel
Numerade Educator
00:58

Problem 41

If a molecule is not very polarizable, how will it respond to an external electric field?

Hunza Gilgit
Hunza Gilgit
Numerade Educator
02:17

Problem 42

What is the relationship between polarizability and dispersion forces?

Hunza Gilgit
Hunza Gilgit
Numerade Educator
00:36

Problem 43

Most gaseous compounds consist of small molecules, while polymers are never gaseous at room temperature. Explain this observation based on intermolecular forces.

Sam Limsuwannarot
Sam Limsuwannarot
Numerade Educator
00:46

Problem 44

Why are dipole-dipole forces typically stronger than dispersion forces?

Anna Miller
Anna Miller
Numerade Educator
02:06

Problem 45

Under what circumstances are ion-dipole forces important?

Nicholas White
Nicholas White
Numerade Educator
01:57

Problem 46

Is hydrogen bonding a chemical bond? Explain your answer.

Ramesh Singh
Ramesh Singh
Numerade Educator
04:06

Problem 47

What is the unique feature of $\mathrm{N}, \mathrm{O}$, and F that causes them to play a role in hydrogen bonding?

Naresh Bagrecha
Naresh Bagrecha
Numerade Educator
01:51

Problem 48

List all the intermolecular interactions that would be found in a sample of the following molecules: (a) $\mathrm{H}_2 \mathrm{~S}$, (b) $\mathrm{CCl}_4$, (c) $\mathrm{CH}_3 \mathrm{OH}$, (d) $\mathrm{NF}_3$, (e) $\mathrm{F}_2$, (f) $\mathrm{NH}_2 \mathrm{OH}$

Adriano Chikande
Adriano Chikande
Numerade Educator
01:34

Problem 49

Arrange the following molecules in order of increasing intermolecular forces: $\mathrm{F}_2, \mathrm{CH}_3 \mathrm{OH}, \mathrm{H}_2 \mathrm{~S}$.

Natalie Johns
Natalie Johns
Numerade Educator
02:17

Problem 50

Arrange the following molecules in order of increasing intermolecular forces: $\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}, \mathrm{C}_3 \mathrm{H}_7 \mathrm{OH}, \mathrm{H}_2 \mathrm{O}$.

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
03:29

Problem 51

Carbon tetrachloride $\left(\mathrm{CCl}_4\right)$ is a liquid at room temperature and pressure, whereas ammonia $\left(\mathrm{NH}_3\right)$ is a gas. How can these observations be rationalized in terms of intermolecular forces?

Theodore Donnell
Theodore Donnell
Numerade Educator
03:06

Problem 52

Explain from a molecular perspective why graphite has properties that are useful for lubrication.

Adriano Chikande
Adriano Chikande
Numerade Educator
01:29

Problem 53

Describe how interactions between molecules affect the vapor pressure of a liquid.

Shazia Naz
Shazia Naz
Numerade Educator
00:46

Problem 54

What makes a chemical compound volatile?

Ronald Prasad
Ronald Prasad
Numerade Educator
01:54

Problem 55

Describe how a ski hill in operation is analogous to dynamic equilibrium.

Kyle Gassaway
Kyle Gassaway
Numerade Educator
01:18

Problem 56

Why does the vapor pressure of a substance require dynamic equilibrium to be measured?

Adriano Chikande
Adriano Chikande
Numerade Educator
01:04

Problem 57

Which substance has the highest boiling point: $\mathrm{CCl}_4$, $\mathrm{BF}_3$, or $\mathrm{SiF}_4$ ?

Shazia Naz
Shazia Naz
Numerade Educator
01:28

Problem 58

Which substance has the lowest vapor pressure: $\mathrm{NF}_3$, $\mathrm{PF}_3$, or $\mathrm{BF}_3$ ?

Lottie Adams
Lottie Adams
Numerade Educator
04:01

Problem 59

A substance is observed to have a high surface tension. What predictions can you make about its vapor pressure and boiling point?

Jake Rempel
Jake Rempel
Numerade Educator
03:24

Problem 60

Suppose that three unknown pure substances are liquids at room temperature. You make vapor pressure
measurements and find that substance $Q$ has a pressure of 110 torr, substance $R$ has a pressure of 42 torr, and substance $S$ has a pressure of 330 torr. If you slowly increase the temperature, which substance will boil first and which will boil last?

Lottie Adams
Lottie Adams
Numerade Educator
01:50

Problem 61

Suppose that three unknown pure substances are liquids at room temperature. You determine that the boiling point of substance A is $53^{\circ} \mathrm{C}$, that of substance B is $117^{\circ} \mathrm{C}$, and that of substance C is $77^{\circ} \mathrm{C}$. Based on this information, rank the three substances in order of their vapor pressures at room temperature.

Susan Hallstrom
Susan Hallstrom
Numerade Educator
00:39

Problem 62

Rank the following hydrocarbons in order of increasing vapor pressure: $\mathrm{C}_2 \mathrm{H}_6, \mathrm{C}_{10} \mathrm{H}_{22}, \mathrm{CH}_4, \mathrm{C}_7 \mathrm{H}_{16}$, $\mathrm{C}_{22} \mathrm{H}_{46}$.

Emily Himsel
Emily Himsel
Numerade Educator
03:34

Problem 63

Draw the meniscus of a fluid in a container where the interactions among the liquid molecules are weaker than those between the liquid and the container molecules.

VS
Vivek Singh
Numerade Educator
00:54

Problem 64

When water is in a tube such as a buret, in which direction does the meniscus curve? What does this observation say about the relative magnitude of adhesion and cohesion in that system?

Riaz Ahmad
Riaz Ahmad
Other Schools
01:34

Problem 65

If shown structures of monomers that might polymerize, what would you look for to determine if the type of polymerization would be addition?

Sima Sarker
Sima Sarker
Numerade Educator
01:33

Problem 66

Why is temperature increased to start most addition polymerization reactions?

George Bennett
George Bennett
Numerade Educator
00:55

Problem 67

What is meant by the term chain termination in a polymerization reaction?

Lottie Adams
Lottie Adams
Numerade Educator
01:34

Problem 68

The monomer of polyvinylchloride is $\mathrm{H}_2 \mathrm{C}=\mathrm{CHCl}$. Draw an example of an isotactic PVC polymer.

Adriano Chikande
Adriano Chikande
Numerade Educator
06:42

Problem 69

Why is there no isotactic or syndiotactic form of polyethylene?

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
01:02

Problem 70

Why are isotactic or syndiotactic polymers often more attractive for materials development?

Aadit Sharma
Aadit Sharma
Numerade Educator
04:04

Problem 71

What are the products of a condensation polymerization reaction?

Nicholas Sacco
Nicholas Sacco
Numerade Educator
01:02

Problem 72

Use the web to find the structure of two types of nylon and describe how they differ from each other.

Narayan Hari
Narayan Hari
Numerade Educator
02:53

Problem 73

Distinguish between a block copolymer and a graft copolymer.

Marissa Turner
Marissa Turner
Numerade Educator
01:21

Problem 74

Use the web to look up the polymers used for six synthetic fibers. Classify the polymers as (a) addition or condensation polymers and (b) as alternating, block or graft copolymers if they are copolymers.

Sima Sarker
Sima Sarker
Numerade Educator
01:38

Problem 75

What is the key physical property that characterizes a thermoplastic polymer?

Manik Pulyani
Manik Pulyani
Numerade Educator

Problem 76

What conditions would prohibit the use of a thermoplastic polymer?

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01:38

Problem 77

What happens molecularly in a thermosetting polymer when it is heated?

Manik Pulyani
Manik Pulyani
Numerade Educator
02:08

Problem 78

What structural characteristics are needed for additives such as plasticizers?

rb
Rabia Bibi
Numerade Educator
04:49

Problem 79

Use the web to find out what pencil erasers are made of. Would it be possible to form a new shape of an eraser by melting it and pouring it into a mold?

Arjun Tibrewal
Arjun Tibrewal
Numerade Educator
02:52

Problem 80

Use the web to find an application where the presence of isotactic, syndiotactic, or atactic polymers affects the physical properties important for an application of a polymer.

Ameer Said
Ameer Said
Numerade Educator
01:35

Problem 81

Use the web to investigate the story of the discovery of buckminsterfullerene. What was the initial reaction to the announcement of this material?

Lottie Adams
Lottie Adams
Numerade Educator
01:35

Problem 82

What was the observation that caused Smalley and co-workers to investigate further and ultimately discover $\mathrm{C}_{60}$ ?

Lottie Adams
Lottie Adams
Numerade Educator
00:59

Problem 83

In the "heat-and-beat" method of materials synthesis, why is heat needed?

Jorge Villanueva
Jorge Villanueva
Numerade Educator

Problem 84

Many experts feel that applications of OLED technology will soon become common. Do a web search to identify emerging uses for OLEDs. Can you find any available commercial products using OLED displays?

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00:31

Problem 85

Use the web to find information about new materials being considered in potential battery technology for the future. Describe the characteristics that are described as helpful for applications in batteries.

Aadit Sharma
Aadit Sharma
Numerade Educator
02:13

Problem 86

There is a new material sometimes referred to as memory metal. Use the web to find information about memory metal. What is this material? Why does the word memory appear in its name?

Shazia Naz
Shazia Naz
Numerade Educator
01:41

Problem 87

If you know the density of a material and the length of the edge of its cubic lattice, how would you determine if it is face-centered cubic, body-centered cubic, or simple cubic? Would you have to look up any information?

Anand Jangid
Anand Jangid
Numerade Educator
05:35

Problem 88

If a pin is run across a magnet a number of times, it will become magnetized. How could this phenomenon be used as an analogy to describe polarization in atoms and molecules?

Daniel Azubuike
Daniel Azubuike
Numerade Educator
04:27

Problem 89

You go into the laboratory to look for a squirt bottle containing acetone. You find two unlabeled bottles with different colored tops suggesting they are different liquids. Unfortunately, you have a terrible cold and cannot tell by smell which one might be acetone. What simple test could you use to determine which liquid is acetone and which is water? How does this test tell you this information?

Sima Sarker
Sima Sarker
Numerade Educator
01:25

Problem 90

A materials engineer, with an eye toward cost, wants to obtain a material whose degree of polymerization is high. What types of measurements must be made in the laboratory to determine whether the degree of polymerization is acceptable?

Manik Pulyani
Manik Pulyani
Numerade Educator
03:55

Problem 91

How is polarizability related to the periodic trends of elements in the periodic table?

Susan Hallstrom
Susan Hallstrom
Numerade Educator
03:16

Problem 92

In previous chapters, we have noted that cryolite is used in refining aluminum. Use the web to look up what this addition does for the process, and relate it to the concepts of intermolecular forces from this chapter.

Kyle Gassaway
Kyle Gassaway
Numerade Educator
02:09

Problem 93

Use the web to look up the percentage of dopant for a commercially available p-type semiconductor. Imagine that you were setting up a process for doping 1 metric ton of silicon with this dopant. (a) What mass would be required? (b) What would be the mole fraction of the dopant?

Chai Santi
Chai Santi
Numerade Educator
02:09

Problem 94

Use the web to look up the percentage of dopant for a commercially available n-type semiconductor. Imagine that you were setting up a process for doping 1 metric ton of silicon with this dopant. (a) What mass would be required? (b) What would be the mole fraction of the dopant?

Chai Santi
Chai Santi
Numerade Educator