Question 1

The empirical formula of an addition polymer ________.

Accepted Answer

The empirical formula of an addition polymer is the same as that of the monomer from which it is formed. This is because addition polymerization does not involve the removal or addition of any atoms or functional groups. The polymer is formed by the repeated addition of monomer units, and therefore the empirical formula remains unchanged. Choices A, B, D, and E involve the addition or subtraction of atoms or functional groups, which is not characteristic of addition polymerization.

Question 2

As a polymer becomes more crystalline, ________.

Accepted Answer

As a polymer becomes more crystalline, none of the listed properties change in a predictable manner. The melting point, density, stiffness, and yield stress of a polymer are dependent on various factors such as the monomer structure, chain length, and molecular weight distribution. Therefore, it is not possible to determine the behavior of these properties solely based on the level of crystallinity.

Question 3

The molecular-orbital model for Ge shows it to be

Accepted Answer

Germanium (Ge) is a semiconductor because it has a small energy gap between the filled valence band and the empty conduction band, allowing electrons to be thermally excited across the gap.

Question 4

The formation of a condensation polymer generally involves ________.

Accepted Answer

The formation of a condensation polymer involves the elimination of a small molecule such as water, alcohol, or HCl, which is released during the joining of monomers.

Question 5

Gallium crystallizes in a primitive cubic unit cell. The length of the unit cell edge is 3.70 Å. The radius of a Ga atom is ________ Å.

Accepted Answer

In a primitive cubic unit cell, the atoms are located at the corners of the cube, and each atom touches the atoms in the adjacent corners. Therefore, the length of the diagonal of the unit cell is equal to four times the radius of a Ga atom. Using the Pythagorean theorem, we can calculate the diagonal length:

diagonal^2 = edge^2 + edge^2 + edge^2 = 3(edge)^2 
diagonal^2 = 3(3.70 Å)^2 
diagonal = 2.55 Å

Thus, the radius of a Ga atom is:

radius = diagonal/4 = 2.55 Å/4 = 0.6375 Å ≈ 0.930 Å

Question 6

CsCl crystallizes in a unit cell that contains the Cs⁺ ion at the center of a cube that has a Cl^- at each corner. Each unit cell contains ________ Cs⁺ ion(s)and ________ Cl^- ion(s), respectively.

Accepted Answer

The unit cell contains one Cs⁺ ion at the center of the cube and one Cl^- ion at each corner of the cube. Therefore, there is only one Cs⁺ ion and one Cl^- ion per unit cell.

Question 7

Which one of the following is an addition polymer with the same structure as polyethylene except that one hydrogen on every other carbon is replaced by a benzene ring?

Accepted Answer

The addition polymer with a benzene ring substitution every other carbon is polystyrene. It has the same structure as polyethylene, except that a hydrogen atom is replaced by a benzene ring. Polyvinyl chloride is made by the addition polymerization of vinyl chloride, polypropylene is made by the polymerization of propylene, polyurethane is made by the condensation polymerization of diisocyanates and diols or polyols, and nylon 6, 6 is made by the condensation polymerization of hexamethylenediamine and adipic acid.

Question 8

CsCl crystallizes in a unit cell that contains a Cs⁺ ion at the center of a cube and a Cl^- ion at each corner. The unit cell of CsCl is ________.

Accepted Answer

CsCl has a body-centered cubic unit cell, which means that the Cs and Cl ions are located at the center of the cube and at the corners, respectively. This is because in a BCC unit cell, there is one atom at the center of the cube and eight atoms at the corners, which is consistent with the arrangement of Cs and Cl ions in CsCl.

Question 9

Which of the following is not a natural polymer?

Accepted Answer

Nylon is a synthetic polymer, meaning it is not naturally occurring, unlike the other options listed which are all found in nature.

Question 10

Inorganic compounds that are semiconductors have an average of ________ valence electrons.

Accepted Answer

Inorganic compounds that are semiconductors typically have an average of 4 valence electrons, as seen in materials like silicon and germanium.

Question 11

If the electronic structure of a solid substance consists of a valence band that is completely filled with electrons and there is a large energy gap to the next set of orbitals, then this substance will be a(n)________.

Accepted Answer

A completely filled valence band means there are no available energy states for electrons to move into, so the substance cannot conduct electricity. The large energy gap also means that it would take a significant amount of energy for an electron to jump from the valence band to the next set of orbitals. This is a characteristic of an insulator.

Question 12

Potassium metal crystallizes in a body-centered cubic structure with a unit cell edge length of 5.31 Å. The radius of a potassium atom is ________ Å.

Accepted Answer

The answer of Potassium metal crystallizes in a body-centered cubic...

Question 13

The properties of graphene include ________.

Accepted Answer

Graphene has high strength due to its 2D crystalline structure and carbon-carbon bonding, and it also has a zero energy gap due to its unique electronic properties. However, it does not have low thermal conductivity, as it actually has very high thermal conductivity due to its high crystal symmetry and low phonon scattering.

Question 14

________ solids consist of atoms or molecules held together by dipole-dipole forces, London dispersion forces, and/or hydrogen bonds.

Accepted Answer

Molecular solids are made up of molecules held together by intermolecular forces, such as dipole-dipole forces, London dispersion forces, and hydrogen bonds. Ionic solids are held together by electrostatic attractions between ions, metallic solids consist of metallic atoms held together by metallic bonding, and covalent-network solids are held together by a network of covalent bonds. The question specifically mentions dipole-dipole forces and London dispersion forces, which are characteristics of molecular solids.

Question 15

An elastomer will fail to regain its original dimensions following a distortion beyond its ________.

Accepted Answer

The elastic limit of an elastomer is the maximum amount of deformation it can undergo before it becomes permanently deformed and fails to regain its original dimensions. Therefore, choice E is the correct answer. The other options listed are not directly related to an elastomer's ability to regain its original dimensions.

Question 16

Which of the following is not classified as a nanomaterial?

Accepted Answer

Isoprene is not classified as a nanomaterial because it is a small organic molecule, whereas the other options listed are all carbon-based materials with unique nanostructures.

Question 17

Natural rubber is too soft and chemically reactive for practical applications. Vulcanization of natural rubber entails ________.

Accepted Answer

Vulcanization of natural rubber involves crosslinking reactive polymer chains with sulfur atoms, which increases the strength, durability, and chemical stability of the material. Unlike the other options, this process does not involve changing the type of polymer or altering its molecular weight.

Question 18

The process of doping can produce a(n)________, which can greatly ________ intrinsic conductivity.

Accepted Answer

The process of doping introduces impurities into a semiconductor material that can increase its intrinsic conductivity. When doping atoms with excess electrons are added, it creates an n-type semiconductor, which has an increased number of free electrons for conduction. Therefore, option A is the correct answer.

Question 19

NaCl crystallizes in a face-centered cubic cell. What is the total number of ions (Na⁺ ions and Cl^- ions)that lie within a unit cell of NaCl?

Accepted Answer

In a face-centered cubic cell, there are 4 ions at the corners (each corner contributes 1/8 of the ion's volume) and 4 ions on the faces (each face contributes 1/2 of the ion's volume). Therefore, there are a total of 8 ions in a unit cell of NaCl.

Question 20

An ionic solid, NaCl (s), dissolves in water because of the ________.

Accepted Answer

The relatively low lattice energy due to the small charges of Na⁺ and Cl^- ions allows water molecules to effectively solvate and separate the ions, facilitating the dissolution process.

Quiz 12: Solids and Modern Materials

The empirical formula of an addition polymer ________.

As a polymer becomes more crystalline, ________.

The molecular-orbital model for Ge shows it to be

The formation of a condensation polymer generally involves ________.

Gallium crystallizes in a primitive cubic unit cell. The length of the unit cell edge is 3.70 Å. The radius of a Ga atom is ________ Å.

CsCl crystallizes in a unit cell that contains the Cs⁺ ion at the center of a cube that has a Cl^- at each corner. Each unit cell contains Cs⁺ ion(s) and Cl^- ion(s) , respectively.

Which one of the following is an addition polymer with the same structure as polyethylene except that one hydrogen on every other carbon is replaced by a benzene ring?

CsCl crystallizes in a unit cell that contains a Cs⁺ ion at the center of a cube and a Cl^- ion at each corner. The unit cell of CsCl is ________.

Which of the following is not a natural polymer?

Inorganic compounds that are semiconductors have an average of ________ valence electrons.

If the electronic structure of a solid substance consists of a valence band that is completely filled with electrons and there is a large energy gap to the next set of orbitals, then this substance will be a(n) ________.

Potassium metal crystallizes in a body-centered cubic structure with a unit cell edge length of 5.31 Å. The radius of a potassium atom is ________ Å.

The properties of graphene include ________.

________ solids consist of atoms or molecules held together by dipole-dipole forces, London dispersion forces, and/or hydrogen bonds.

An elastomer will fail to regain its original dimensions following a distortion beyond its ________.

Which of the following is not classified as a nanomaterial?

Natural rubber is too soft and chemically reactive for practical applications. Vulcanization of natural rubber entails ________.

The process of doping can produce a(n) , which can greatly intrinsic conductivity.

NaCl crystallizes in a face-centered cubic cell. What is the total number of ions (Na⁺ ions and Cl^- ions) that lie within a unit cell of NaCl?

An ionic solid, NaCl (s) , dissolves in water because of the ________.

Quiz 12: Solids and Modern Materials

The empirical formula of an addition polymer ________.

As a polymer becomes more crystalline, ________.

The molecular-orbital model for Ge shows it to be

The formation of a condensation polymer generally involves ________.

Gallium crystallizes in a primitive cubic unit cell. The length of the unit cell edge is 3.70 Å. The radius of a Ga atom is ________ Å.

CsCl crystallizes in a unit cell that contains the Cs+ ion at the center of a cube that has a Cl- at each corner. Each unit cell contains ________ Cs+ ion(s) and ________ Cl- ion(s) , respectively.

Which one of the following is an addition polymer with the same structure as polyethylene except that one hydrogen on every other carbon is replaced by a benzene ring?

CsCl crystallizes in a unit cell that contains a Cs+ ion at the center of a cube and a Cl- ion at each corner. The unit cell of CsCl is ________.

Which of the following is not a natural polymer?

Inorganic compounds that are semiconductors have an average of ________ valence electrons.

If the electronic structure of a solid substance consists of a valence band that is completely filled with electrons and there is a large energy gap to the next set of orbitals, then this substance will be a(n) ________.

Potassium metal crystallizes in a body-centered cubic structure with a unit cell edge length of 5.31 Å. The radius of a potassium atom is ________ Å.

The properties of graphene include ________.

________ solids consist of atoms or molecules held together by dipole-dipole forces, London dispersion forces, and/or hydrogen bonds.

An elastomer will fail to regain its original dimensions following a distortion beyond its ________.

Which of the following is not classified as a nanomaterial?

Natural rubber is too soft and chemically reactive for practical applications. Vulcanization of natural rubber entails ________.

The process of doping can produce a(n) ________, which can greatly ________ intrinsic conductivity.

NaCl crystallizes in a face-centered cubic cell. What is the total number of ions (Na+ ions and Cl- ions) that lie within a unit cell of NaCl?

An ionic solid, NaCl (s) , dissolves in water because of the ________.

CsCl crystallizes in a unit cell that contains the Cs⁺ ion at the center of a cube that has a Cl^- at each corner. Each unit cell contains Cs⁺ ion(s) and Cl^- ion(s) , respectively.

CsCl crystallizes in a unit cell that contains a Cs⁺ ion at the center of a cube and a Cl^- ion at each corner. The unit cell of CsCl is ________.

The process of doping can produce a(n) , which can greatly intrinsic conductivity.

NaCl crystallizes in a face-centered cubic cell. What is the total number of ions (Na⁺ ions and Cl^- ions) that lie within a unit cell of NaCl?