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Chemistry A Molecular Approach

Nivaldo J. Tro

Chapter 12

Solids and Modern Materials - all with Video Answers

Educators

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Chapter Questions

00:24

Problem 1

What is graphene? Why is graphene unique?

Amy Jiang
Amy Jiang
Numerade Educator
16:20

Problem 2

Explain the basic principles involved in X-ray crystallography. Include Bragg's law in your explanation.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:29

Problem 3

What is a crystalline lattice? How is the lattice represented with the unit cell?

Amy Jiang
Amy Jiang
Numerade Educator
07:42

Problem 4

Make a drawing of each unit cell: simple cubic, body-centered cubic, and face-centered cubic.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
10:39

Problem 5

For each of the cubic cells in the previous problem, give the coordination number, edge length in terms of $r,$ and number of atoms per unit cell.

CK
Caroline Kaplan
Numerade Educator
07:30

Problem 6

What is the difference between hexagonal closest packing and cubic closest packing? What are the unit cells for each of these structures?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:42

Problem 7

What are the three basic types of solids and the composite units of each? What types of forces hold each type of solid together?

Amy Jiang
Amy Jiang
Numerade Educator
01:23

Problem 8

What are the three categories of atomic solids?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:40

Problem 9

What kinds of forces hold each of the three basic categories of atomic solids together?

Amy Jiang
Amy Jiang
Numerade Educator
00:55

Problem 10

What is a polymorph?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:44

Problem 11

In an ionic compound, how are the relative sizes of the cation and anion related to the coordination number of the crystal structure?

Amy Jiang
Amy Jiang
Numerade Educator
14:10

Problem 12

Show how the cesium chloride, sodium chloride, and zinc blende unit cells each contain a cation-to anion ratio of $1 : 1 .$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:56

Problem 13

Show how the fluorite structure accommodates a cation-to-anion ratio of $1 : 2 .$

Amy Jiang
Amy Jiang
Numerade Educator
08:35

Problem 14

Name and describe the different allotropes of carbon.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:39

Problem 15

What are silicates? What is quartz?

Amy Jiang
Amy Jiang
Numerade Educator
02:24

Problem 16

What is the definition of a ceramic? What are the three categories of ceramics?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:01

Problem 17

List the major and minor components of Portland cement. What is the difference between the hardening process of Portland cement and the hardening process of clays?

Amy Jiang
Amy Jiang
Numerade Educator
03:29

Problem 18

How is concrete made from Portland cement? What advantage does concrete have for building compared to the construction methods that predated the development of concrete?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:32

Problem 19

Describe what happens on the molecular level when silica is heated and then cooled to make glass.

Amy Jiang
Amy Jiang
Numerade Educator
03:22

Problem 20

Describe the difference between vitreous silica and soda-lime glass. What are some advantages and disadvantages of each of these types of glass?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:46

Problem 21

In band theory of bonding for solids, what is a band? What is the difference between the valence band and the conduction band?

Amy Jiang
Amy Jiang
Numerade Educator
04:49

Problem 22

In band theory of bonding for solids, what is a band gap? How does the band gap differ in metals, semiconductors, and insulators?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:55

Problem 23

Explain how doping can increase the conductivity of a semiconductor. What is the difference between an n-type semiconductor and a p-type semiconductor?

Amy Jiang
Amy Jiang
Numerade Educator
02:45

Problem 24

What is the trend in the size of the band gap as you move down the column of the group 4 A elements?

Ronald Prasad
Ronald Prasad
Numerade Educator
00:19

Problem 25

What is a polymer? What is the difference between a polymer and a copolymer?

Amy Jiang
Amy Jiang
Numerade Educator
02:18

Problem 26

How do an addition polymer and a condensation polymer differ from each other?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:32

Problem 27

An $\mathrm{X}$ -ray beam with $\lambda=154 \mathrm{pm}$ incident on the surface of a crystal produced a maximum reflection at an angle of $\theta=28.3^{\circ} .$ Assuming $n=1,$ calculate the separation between layers of atoms in the crystal.

Amy Jiang
Amy Jiang
Numerade Educator
03:42

Problem 28

An $\mathrm{X}$ -ray beam of unknown wavelength is diffracted from a NaCl surface. If the interplanar distance in the crystal is 286 $\mathrm{pm},$ and the angle of maximum reflection is found to be $7.23^{\circ}$ what is the wavelength of the X-ray beam? (Assume $n=1 . )$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:48

Problem 29

Determine the number of atoms per unit cell for each metal. (a) Polonium (b) Tungsten (c) Nickel

Amy Jiang
Amy Jiang
Numerade Educator
04:35

Problem 30

Determine the coordination number for each structure. (a) Gold (b) Ruthenium (c) Chromium

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:28

Problem 31

Calculate the packing efficiency of the body-centered cubic unit cell. Show your work.

Amy Jiang
Amy Jiang
Numerade Educator
08:25

Problem 32

Calculate the packing efficiency of the face-centered cubic unit cell. Show your work.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
04:22

Problem 33

Platinum crystallizes with the face-centered cubic unit cell. The radius of a platinum atom is 139 pm. Calculate the edge length of the unit cell and the density of platinum in $\mathrm{g} / \mathrm{cm}^{3} .$

Amy Jiang
Amy Jiang
Numerade Educator
11:29

Problem 34

Molybdenum crystallizes with the body-centered unit cell. The radius of a molybdenum atom is 136 $\mathrm{pm} .$ Calculate the edge length of the unit cell and the density of molybdenum.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
06:45

Problem 35

Rhodium has a density of 12.41 $\mathrm{g} / \mathrm{cm}^{3}$ and crystallizes with the face-centered cubic unit cell. Calculate the radius of a rhodium atom.

Amy Jiang
Amy Jiang
Numerade Educator
10:43

Problem 36

Barium has a density of 3.59 $\mathrm{g} / \mathrm{cm}^{3}$ and crystallizes with the body-centered cubic unit cell. Calculate the radius of a barium atom.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
03:01

Problem 37

Polonium crystallizes with a simple cubic structure. It has a density of 9.3 $\mathrm{g} / \mathrm{cm}^{3}$ , a radius of $167 \mathrm{pm},$ and a molar mass of 209 $\mathrm{g} / \mathrm{mol} .$ Use these data to calculate Avogadro's number (the number of atoms in one mole).

Amy Jiang
Amy Jiang
Numerade Educator
10:52

Problem 38

Palladium crystallizes with a face-centered cubic structure. It has a density of $12.0 \mathrm{g} / \mathrm{cm}^{3},$ a radius of $138 \mathrm{pm},$ and a molar mass of 106.42 $\mathrm{g} / \mathrm{mol} .$ Use these data to calculate Avogadro's number.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:51

Problem 39

Identify each solid as molecular, ionic, or atomic.$$\begin{array}{l}{\text { a. } \operatorname{Ar}(s)} \\ {\text { b. } \mathrm{H}_{2} \mathrm{O}(s)} \\ {\text { c. } \mathrm{K}_{2} \mathrm{O}(s)} \\ {\text { d. Fe }(s)}\end{array}$$

Amy Jiang
Amy Jiang
Numerade Educator
02:42

Problem 40

Identify each solid as molecular, ionic, or atomic.$$\begin{array}{l}{\text { a. } \mathrm{CaCl}_{2}(\mathrm{s})} \\ {\text { b. } \mathrm{CO}_{2}(s)} \\ {\text { c. } \mathrm{Ni}(s)} \\ {\text { d. } \mathrm{I}_{2}(s)}\end{array}$$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:42

Problem 41

Which solid has the highest melting point? Why? $\operatorname{Ar}(s), \mathrm{CCl}_{4}(s), \mathrm{LiCl}(s), \mathrm{CH}_{3} \mathrm{OH}(s)$

Amy Jiang
Amy Jiang
Numerade Educator
03:45

Problem 42

Which solid has the highest melting point? Why? $$ \mathrm{C}(s, \text { diamond }), \mathrm{Kr}(s), \mathrm{NaCl}(s), \mathrm{H}_{2} \mathrm{O}(s)$$

Ronald Prasad
Ronald Prasad
Numerade Educator
02:20

Problem 43

Which solid in each pair has the higher melting point and why? $$\begin{array}{l}{\text { a. } \mathrm{TiO}_{2}(s) \text { or HOOH }(s)} \\ {\text { b. } \mathrm{CCl}_{4}(s) \text { or } \operatorname{SiCl}_{4}(s)} \\ {\text { c. } \mathrm{Kr}(s) \text { or } \mathrm{Xe}(s)} \\ {\text { d. } \mathrm{NaCl}(s) \text { or } \mathrm{CaO}(s)}\end{array}$$

Amy Jiang
Amy Jiang
Numerade Educator
03:45

Problem 44

Which solid in each pair has the higher melting point and why? $$ \begin{array}{l}{\text { a. Fe }(s) \text { or } \mathrm{CCl}_{4}(s)} \\ {\text { b. } \mathrm{KCl}(s) \text { or } \mathrm{HCl}(s)} \\ {\text { c. Ti }(s) \text { or } \mathrm{Ne}(s)} \\ {\text { d. } \mathrm{H}_{2} \mathrm{O}(s) \text { or } \mathrm{H}_{2} \mathrm{S}(s)}\end{array}$$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
04:34

Problem 45

An oxide of titanium crystallizes with the unit cell shown here (titanium $=$ gray; oxygen $=$ red. What is the formula of the oxide?

Suendues Noori
Suendues Noori
Numerade Educator
03:01

Problem 46

An oxide of rhenium crystallizes with the unit cell shown here (rhenium = gray; oxygen =red). What is the formula of the oxide?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
02:41

Problem 47

The unit cells for cesium chloride and barium chloride are shown here. Show that the ratio of cations to anions in each unit cell corresponds to the ratio of cations to anions in the formula of each compound.

Amy Jiang
Amy Jiang
Numerade Educator
04:32

Problem 48

The unit cells for lithium oxide and silver iodide are shown here. Show that the ratio of cations to anions in each unit cell corresponds to the ratio of cations to anions in the formula of each compound.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:02

Problem 49

Identify the structure of each of the two unit cells shown in Problem 47 as the rock salt structure, zinc blende structure, fluorite structure, antifluorite structure, or none of these.

Amy Jiang
Amy Jiang
Numerade Educator
05:25

Problem 50

Identify the structure of each of the two unit cells shown in Problem 48 as the rock salt structure, zinc blende structure, fluorite structure, antifluorite structure, or none of these.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:18

Problem 51

Consider the rock salt structure in Figure $12.15 .$ What type of structure would result if all the anions were somehow removed, leaving only cations?

Amy Jiang
Amy Jiang
Numerade Educator
02:56

Problem 52

Consider the zinc blende structure in Figure $12.16 .$ What type of structure would result if the remaining tetrahedral sites in the unit cell were also filled with cations?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:36

Problem 53

Classify each of the following as a component of a silicate ceramic, an oxide ceramic, or a nonoxide ceramic. $$\text{ a. } \mathrm{B}_{4} \mathrm{C} \quad \text { b. } \mathrm{Mg}_{2} \mathrm{SiO}_{4} \quad \text { c. } \mathrm{MoSi}_{2}$$

Amy Jiang
Amy Jiang
Numerade Educator
01:47

Problem 54

Classify each of the following as a component of a silicate ceramic, an oxide ceramic, or a nonoxide ceramic. $$\begin{array}{l}{\text { a. TiB }_{2}} \\ {\text { b. } \mathrm{ZrO}_{2}} \\ {\text { c. } \mathrm{NaAlSi}_{3} \mathrm{O}_{8}}\end{array}$$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:23

Problem 55

What are the name and formula of the compound commonly used in the manufacture of glass to reduce its tendency to crack or shatter under thermal shock?

Amy Jiang
Amy Jiang
Numerade Educator
01:16

Problem 56

What are the name and formula of the compound commonly used in the manufacture of glass to increase the index of refraction?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:36

Problem 57

One of the key components in the manufacture of Portland cement is $\mathrm{Ca}_{3} \mathrm{SiO}_{5},$ a compound that is obtained by firing the reactants in a kiln at $1400-1500^{\circ} \mathrm{C}$ . Assign an oxidation state to each element in this compound.

Amy Jiang
Amy Jiang
Numerade Educator
02:50

Problem 58

Replacement of aluminum ions in kaolinite with magnesium ions yields a compound with the formula $\operatorname{Mg}_{3} 5 \mathrm{i}_{2} \mathrm{O}_{5}(\mathrm{OH})_{4}$ Assign an oxidation state to each element in this compound.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:08

Problem 59

Which solid would you expect to have little or no band gap? $$ \begin{array}{l}{\text { a. } \mathrm{Zn}(\mathrm{s})} \\ {\text { b. } \mathrm{Si}(s)} \\ {\text { c. } \mathrm{As}(s)}\end{array}$$

Lottie Adams
Lottie Adams
Numerade Educator
03:33

Problem 60

Which solid would you expect to have the largest band gap? $$ \begin{array}{l}{\text { a. } \operatorname{As}(s)} \\ {\text { b. } \mathrm{Sb}(s)} \\ {\text { c. } \mathrm{Bi}(s)}\end{array}$$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:30

Problem 61

How many molecular orbitals are present in the conduction band of a lithium crystal with a mass of 11.2 $\mathrm{g} ?$

David Collins
David Collins
Numerade Educator
01:04

Problem 62

How many molecular orbitals are present in the valence band of a sodium crystal with a mass of 5.45 $\mathrm{g}$ ?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
03:16

Problem 63

A substance has a band gap of 6.9 eV at 273 $\mathrm{K}$ . Is this substance best classified as an insulator, a semiconductor, or a metal?

wa
Wegood Awad
Numerade Educator
01:49

Problem 64

A substance has a band gap of 0.85 eV at 273 $\mathrm{K}$ . Is this substance best classified as an insulator, a semiconductor, or a metal?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:42

Problem 65

Indicate if each solid forms an n-type or a p-type semiconductor. $\begin{array}{l}{\text { a. silicon doped with gallium }} \\ {\text { b. germanium doped with antimony }}\end{array}$

Amy Jiang
Amy Jiang
Numerade Educator
07:05

Problem 66

Indicate if each solid forms an n-type or a p-type semiconductor.$\begin{array}{l}{\text { a. silicon doped with gallium }} \\ {\text { b. germanium doped with antimony }}\end{array}$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:28

Problem 67

Does a photon of red light with a frequency of $4.29 \times 10^{14} \mathrm{Hz}$ have sufficient energy to promote an electron from the valence band to the conduction band in a sample of silicon (the band gap in silicon is 1.11 $\mathrm{eV}$ )?

Amy Jiang
Amy Jiang
Numerade Educator
08:01

Problem 68

Which wavelength of light (in $\mathrm{nm}$ ) is emitted if an electron moves from the conduction band to the valence band in a sample of diamond (diamond has a band gap of 5.5 eV)?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:36

Problem 69

Teflon is an addition polymer formed from the monomer shown here. Draw the structure of the polymer.

Matthew Hurlock
Matthew Hurlock
Numerade Educator
01:10

Problem 70

Saran, the polymer used to make saran wrap, is an addition polymer formed from two monomers--vinylidene chloride and vinyl chloride. Draw the structure of the polymer. (Hint: The monomers alternate.)

David Collins
David Collins
Numerade Educator
01:48

Problem 71

One kind of polyester is a condensation copolymer formed from terephthalic acid and ethylene glycol. Draw the structure of the dimer. [Hint: Water (circled) is eliminated when the bond between the monomers forms.]

Matthew Hurlock
Matthew Hurlock
Numerade Educator
02:09

Problem 72

Nomex, a condensation copolymer used by firefighters because of its flame-resistant properties, forms from isophthalic acid and $m$ -aminoaniline. Draw the structure of the dimer. (Hint: Water is eliminated when the bond between the monomers forms.)

Ronald Prasad
Ronald Prasad
Numerade Educator
00:28

Problem 73

Polyacetylene is an addition polymer with the structure shown here. Draw the structure of the monomer.

Amy Jiang
Amy Jiang
Numerade Educator
02:34

Problem 74

Polyacrylonitrile (PAN) is an addition polymer with the structure shown here. Draw the structure of the monomer.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:56

Problem 75

Polyacrylonitrile (PAN) is an addition polymer with the structure shown here. Draw the structure of the monomer.Assuming this polymer was formed from the monomer shown here plus another monomer, provide a possible structure for the other monomer that would be required to form Lexan.

Lottie Adams
Lottie Adams
Numerade Educator
01:26

Problem 76

Consider the condensation polymer with the structure shown here: Assuming this polymer was formed from the monomer shown below plus another monomer, provide the structure of the other monomer that would be required to form this polymer.

David Collins
David Collins
Numerade Educator
01:09

Problem 77

Silver iodide crystallizes in the zinc blende structure. The separation between nearest-neighbor cations and anions is approximately 325 pm, and the melting point is $558^{\circ} \mathrm{C}$ . Cesium chloride, by contrast, crystallizes in the structure shown in Figure 12.14 . Even though the separation between nearest-neighbor cations and anions is greater $(348 \mathrm{pm})$ , the melting point of cesium chloride is higher $\left(645^{\circ} \mathrm{C}\right) .$ Explain.

Amy Jiang
Amy Jiang
Numerade Educator
05:00

Problem 78

Copper iodide crystallizes in the zinc blende structure. The separation between nearest neighbor cations and anions is approximately $311 \mathrm{pm},$ and the melting point is $606^{\circ} \mathrm{C} .$ Potassium chloride, by contrast, crystallizes in the rock salt structure. Even though the separation between nearest-neighbor cations and anions is greater $(319 \mathrm{pm}),$ the melting point of potassium chloride is higher $\left(776^{\circ} \mathrm{C}\right) .$ Explain.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:40

Problem 79

Consider the face-centered cubic structure shown here: $\begin{array}{l}{\text { a. What is the length of the line (labeled } c ) \text { that runs }} \\ {\text { diagonally across one of the faces of the cube in terms of }} \\ {r(\text { the atomic radius)? }} \\ {\text { b. Use the answer to part a and the Pythagorean theorem to }} \\ {\text { derive the expression for the edge length ( }(l) \text { in terms of } r .}\end{array}$

Ronald Prasad
Ronald Prasad
Numerade Educator
04:41

Problem 80

Consider the body-centered cubic structure shown here:Consider the body-centered cubic structure shown here:$\begin{array}{l}{\text { a. What is the length of the line (labeled c) that runs from one }} \\ {\text { corner of the cube diagonally through the center of the cube }} \\ {\text { to the other corner in terms of } r \text { (the atomic radius)? }}\end{array}$$\begin{array}{l}{\text { b. Use the Pythagorean theorem to derive an expression for the }} \\ {\text { length of the line (labeled } b ) \text { that runs diagonally across one }} \\ {\text { of the faces of the cube in terms of the edge length }(l) .} \\ {\text { c. Use the answer to parts a and b along with the Pythagorean }} \\ {\text { theorem to derive the expression for the edge length (l) in }} \\ {\text { terms of } r .}\end{array}$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:36

Problem 81

The volume of a unit cell of diamond is $0.0454 \mathrm{nm}^{3},$ and the density of diamond is 3.52 $\mathrm{g} / \mathrm{cm}^{3} .$ Find the number of carbon atoms in a unit cell of diamond.

Amy Jiang
Amy Jiang
Numerade Educator
04:05

Problem 82

The density of an unknown metal is $12.3 \mathrm{g} / \mathrm{cm}^{3},$ and its atomic radius is 0.134 $\mathrm{nm} .$ It has a face-centered cubic lattice. Find the atomic mass of this metal.

Ronald Prasad
Ronald Prasad
Numerade Educator
01:42

Problem 83

An unknown metal is found to have a density of 7.8748 $\mathrm{g} / \mathrm{cm}^{3}$ and to crystallize in a body-centered cubic lattice. The edge of the unit cell is 0.28664 $\mathrm{nm}$ . Calculate the atomic mass of the metal.

Amy Jiang
Amy Jiang
Numerade Educator
04:36

Problem 84

When spheres of radius $r$ are packed in a body-centered cubic arrangement, they occupy 68.0$\%$ of the available volume.Use the fraction of occupied volume to calculate the value of $a,$
the length of the edge of the cube, in terms of $r .$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:39

Problem 85

Potassium chloride crystallizes in the rock salt structure. Estimate the density of potassium chloride using the ionic radii provided in Chapter $8 .$

Amy Jiang
Amy Jiang
Numerade Educator
11:49

Problem 86

Calculate the fraction of empty space in cubic closest packing to five significant figures.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
02:56

Problem 87

A tetrahedral site in a closest-packed lattice is formed by four spheres at the corners of a regular tetrahedron. This is equivalent to placing the spheres at alternate corners of a cube. In such
a closest-packed arrangement the spheres are in contact, and if the spheres have a radius $r$ , the diagonal of the face of the cube is 2$r .$ The tetrahedral hole is inside the middle of the cube. Find
the length of the body diagonal of this cube and then find the radius of the tetrahedral hole.

Adriano Chikande
Adriano Chikande
Numerade Educator
03:05

Problem 88

X-ray diffractometers often use metals that have had their core electrons excited as a source of X-rays. Consider the 2$p \longrightarrow 1 s$ transition for copper, which is called the $K \alpha$ transition. Calculate the wavelength of $X$ -rays $($ in $\hat{A})$ given off by the $K \alpha$
transition if the energy given off by a mole of copper atoms is $7.77 \times 10^{5} \mathrm{kJ} .\left(1 \hat{\mathrm{A}}=10^{-10} \mathrm{m}\right)$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:56

Problem 89

Why is it necessary to use the $K \alpha$ transition $(2 p \longrightarrow 1 s)$ in copper (see Problem 88$)$ to generate $X$ -rays? Why not use, for example, the 4$s \longrightarrow 3 p$ transition?

Matthew Hurlock
Matthew Hurlock
Numerade Educator
03:49

Problem 90

In certain cases where X-ray diffraction is unsuitable for determining the structure of a crystal, neutron diffraction can be used. Instead of $X$ -rays, a beam of neutrons is used to analyze the
sample. Calculate the velocity of a beam of neutrons with a wavelength of 2.00$\hat{\mathrm{A}}$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:26

Problem 91

The structure of the addition polymer polypropylene is shown in Table $12.3 .$ $\begin{array}{l}{\text { a. Draw the structure of the monomer. }} \\ {\text { b. Show how an alternate version of the polypropylene poly- }} \\ {\text { mer (with a different arrangement) could be formed from }} \\ {\text { the monomer you found in part a. }}\end{array}$

Amy Jiang
Amy Jiang
Numerade Educator
12:23

Problem 92

Perovskite is a compound with a cubic unit cell and has a strontium atom at the center of the cell, titanium atoms at the corners of the unit cell, and oxygen atoms at the centers of each face of the unit cell.$\begin{array}{l}{\text { c. If the edge length of the unit cell is } 3.905 \text { Ä, calculate the }} \\ {\text { density of perovskite in } \mathrm{g} / \mathrm{cm}^{3} .}\end{array}$

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:23

Problem 93

A compound with the formula $\mathrm{Rb}_{3} \mathrm{C}_{60}$ has been shown to demonstrate superconductivity below 30.0 $\mathrm{K}$ . Given that the $\mathrm{C}_{60}$ molecules have a face-centered cubic arrangement, which of the tetrahedral and octahedral sites are occupied by Rb atoms?

Lottie Adams
Lottie Adams
Numerade Educator
04:37

Problem 94

Despite Dalton's laws, it is now known that many ionic compounds do not always contain atoms in small integer ratios. For example, a sample of iron(II) oxide may, in fact, contain a significant amount of $\mathrm{Fe}^{3+}$ in addition to $\mathrm{Fe}^{2+} .$ This is an example of a nonstoichiometric compound. A sample of iron(II) oxide is found to be 75.65$\%$ iron by mass. Determine the percentage of $\mathrm{Fe}^{3+}$ ions in the sample.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
00:14

Problem 95

During the glass manufacturing process, the liquid must be cooled relatively quickly to form the glass. Why?

Ivan Kochetkov
Ivan Kochetkov
Numerade Educator
03:04

Problem 96

Why are $X$ -rays used for crystallography? Why not use some other, more accessible type of electromagnetic radiation such as ultraviolet light?

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:59

Problem 97

Compare the crystal structure of diamond (C) and zinc blende (ZnS). What are the key similarities and differences between the two structures?

Matthew Hurlock
Matthew Hurlock
Numerade Educator
00:55

Problem 98

In X-ray crystallography, a small amount of oil is often used to mount the crystal sample on a glass fiber. Explain why neither the oil nor the glass fiber interferes with the diffraction pattern of the crystal.

Wilson Ma
Wilson Ma
The University of Alabama
01:37

Problem 99

Which is not likely to lead to an increase in electrical conductivity? $\begin{array}{l}{\text { a. Increasing the temperature of a semiconductor }} \\ {\text { b. Choosing a semiconductor with a smaller band gap }} \\ {\text { c. Doping the semiconductor }} \\ {\text { d. All of the above would likely lead to an increase in electrical }} \\ {\text { conductivity. }}\end{array}$

Erwin Ni
Erwin Ni
Numerade Educator
25:43

Problem 100

Have each group member select one of the cubic crystalline lattices. Learn everything you can about your lattice and present it to the group.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:27

Problem 101

Using group members to play the role of atoms or molecules, demonstrate the main structural features of the following categories of crystalline solids: molecular solid, ionic solid, non-bonded solid, metallic solid, network covalent solid. Clearly identify what you represent and how you are representing various interactions between particles (e.g., covalent bond, ionic bond, etc..

Matthew Hurlock
Matthew Hurlock
Numerade Educator
05:04

Problem 102

Make a list of questions you would need to ask in order to classify a solid into one of the categories of crystalline solids (molecular solid, ionic solid, nonbonded solid, metallic solid, and network
covalent solid.). Determine a good order to ask them. (You may need a branching decision tree.) Once you have agreed on a good set of questions, have each group member choose a substance from the chapter and then have the other group members ask the questions in turn until the correct classification is reached. You may agree to edit your questions if you discover ways to improve them when you are using your decision tree.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
01:33

Problem 103

Have each group member select and study a material from the section on ceramics, cement, and glass. Take turns describing your material to the group, and see if they can identify the type of material based on your description (without consulting the text).

Matthew Hurlock
Matthew Hurlock
Numerade Educator
11:48

Problem 104

Describe how a common object or toy (e.g., a train, building blocks, or beads on a string) could represent the structure of a polymer. Describe how the following terms would be represented using your model: monomer, dimer, addition polymer, condensation polymer, branching.

Matthew Bamidele
Matthew Bamidele
Numerade Educator
05:52

Problem 105

The use of hydrogen as a fuel to power cars and trucks is an active research area. One challenge is storing the hydrogen, which is problematic because the steel fuel tanks are heavy and the hydrogen gas can explode in a crash. Some metals have the ability to absorb hydrogen gas to form metal hydrides. For example, niobium and magnesium each react with hydrogen gas to form niobium hydride and magnesium hydride, respectively: $$\begin{array}{ll}{\mathrm{Nb}(s)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{NbH}_{2}(s)} & {\Delta H=-127 \mathrm{kJ} / \mathrm{mol} \mathrm{H}_{2}} \\ {\mathrm{Mg}(s)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{MgH}_{2}(s)} & {\Delta H=-77 \mathrm{kJ} / \mathrm{mol} \mathrm{H}_{2}}\end{array}$$ Metal hydrides make it possible to store a large amount of hydrogen in a small space. Once each of these reactions occurs,
the hydrogen is stored in the solid metal hydride. After a metal hydride is formed, the process can be reversed. Not all elements form hydrides. Table a lists some elements that form hydrides and some that do not. Figure a $\#$ shows the relationship of the reaction enthalpies as a function of hydrogen content for several hydrides.

David Collins
David Collins
Numerade Educator