Unit 12 Practice Test

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Unit 12 Practice Test

Multiple Choice

Identify the choice that best completes the statement or answers the question.

____ 1) A solid has a very high melting point, great hardness, and poor electrical conduction. This is a(n) ____ solid. A) ionic

B) molecular C) metallic

D) covalent network

E) metallic and covalent network

____ 2) Which one of the following cannot form a solid with a lattice based on the sodium chloride structure? A) NaBr

B) LiF C) RbI D) CuO E) CuCl2

____ 3) What portion of the volume of each atom or ion on the face of a unit cell is actually within the unit cell? A) 1/2

B) 1/4 C) 3/4 D) all of it E) none of it

____ 4) For a substitutional alloy to form, the two metals combined must have similar A) ionization potential and electron affinity.

B) number of valance electrons and electronegativity. C) reduction potential and size.

D) atomic radii and chemical bonding properties. E) band gap and reactivity.

____ 5) Alloys generally differ from compounds in that A) the former always contain some carbon. B) the former always contain some iron.

C) the former always have semiconductor properties.

D) the atomic ratios of the constituent elements in the former are not fixed and may vary over a wide range.

E) the former never contain a transition element.

____ 6) 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) ____.

A) alloy B) insulator C) conductor D) semiconductor

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Name: ________________________ ID: A

____ 7) The molecular-orbital model for Ge shows it to be

A) a conductor, because all the lower energy band orbitals are filled and the gap between the lower and higher bands is large.

B) an insulator, because all the lower energy band orbitals are filled and the gap between the lower and higher bands is large.

C) a semiconductor, because the gap between the filled lower and empty higher energy bands is relatively small.

D) a semiconductor, because the gap between the filled lower and empty higher energy bands is large.

E) a conductor, because its lower energy band orbitals are only partially filled. ____ 8) As a polymer becomes more crystalline, ____.

A) its melting point decreases B) its density decreases C) its stiffness decreases D) its yield stress decreases E) None of the above is correct.

____ 9) 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.

A) 7.40 B) 3.70 C) 1.85 D) 0.930

E) Insufficient data is given.

____ 10) The transition metals in group ____ have the highest melting points. A) 4B

B) 3B C) 6B D) 8B E) 2B

____ 11) The ____ lattice is one of the five two-dimensional lattices in which the lattice vectors a and b are equal and the γ angle between them is 90°.

A) square B) rectangular C) hexagonal D) rhombic E) oblique

____ 12) Of the following, only ____ is not a polymer. A) dental amalgam

B) cellulose C) Teflon D) plastic E) protein

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____ 13) The correct abbreviation for the polymer low-density polyethylene is ____. A) LDPE B) PP C) P D) PETE E) HDPE Short Answer

1) When lattice points occur only at the corners of a unit cell, the cell is called ________.

2) When lattice points occur at the corners and at the center of a unit cell, the cell is called ________. 3) When lattice points occur at the center of each face, as well as each corner of a unit cell, the cell is called

________.

4) A material that contains more than one element and has the characteristic properties of metals is called a(n) ________.

5) How many atoms are contained in a face-centered cubic unit cell?

6) Chromium crystallizes in a body-centered cubic unit cell. There are ________ chromium atoms per unit cell. 7) What two metals are alloyed to produce sterling silver?

8) Semiconductors are less conductive than metals because of ________ gap.

9) ________ are materials characterized by an energy gap between a filled valence band and an empty conduction band.

10) The process of adding controlled amounts of impurity atoms to a material is known as ________. 11) The dopant atoms in an n-type semiconductor have ________ electrons than the host material. 12) Semiconductor particles with diameters of 1–10 nm are called ________.

13) Write the chemical formulas for both polyethylene and the monomer from which it is formed. 14) Nylon is formed by the reaction of a(n) ________ with a(n) ________.

15) Polymers formed from two different monomers are called ________.

16) In addition to differences in their average molecular mass, HDPE and LDPE differ in their degree of ________ and their ________ of the chains.

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Name: ________________________ ID: A

True/False

Indicate whether the statement is true or false.

____ 1) The type of solid that is characterized by low melting point, softness, and low electrical conduction is a covalent-network solid.

____ 2) Many metals are ductile, which means that they can be hammered into thin sheets. ____ 3) Silicon technology is based on the fact that silicon oxide is a chemically stable conductor. ____ 4) Polyethylene is formed by a condensation reaction.

____ 5) Vulcanization involves heating rubber with sulfur dioxide to produce a thermosetting polymer. ____ 6) A plasticizer makes a polymer more pliable by reducing the interactions between polymer chains.

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Unit 12 Practice Test

Answer Section

MULTIPLE CHOICE

1) ANS: D PTS: 1 DIF: 3 REF: Page Ref: 12.1 OBJ: 12.1; G2

2) ANS: E PTS: 1 DIF: 1 REF: Page Ref: 12.2 OBJ: 12.2; G2

3) ANS: A PTS: 1 DIF: 3 REF: Page Ref: 12.3 OBJ: 12.3, 12.5; G2

6) ANS: B PTS: 1 DIF: 4 REF: Page Ref: 12.5 OBJ: 12.5; G2

7) ANS: C PTS: 1 DIF: 5 REF: Page Ref: 12.7 OBJ: 12.7; G2

8) ANS: E PTS: 1 DIF: 2 REF: Page Ref: 12.8 OBJ: 12.8; G2

9) ANS: C PTS: 1 DIF: 2 REF: Page Ref: 12.3 OBJ: 12.3, 12.5; G2

10) ANS: C PTS: 1 DIF: 2 REF: Page Ref: 12.4 OBJ: 12.4; G2

11) ANS: A PTS: 1 DIF: 3 REF: Page Ref: 12.2 OBJ: 12.2; G2

SHORT ANSWER 1) ANS:

primitive cubic

PTS: 1 DIF: 2 REF: Page Ref: 12.2 OBJ: 12.2; G2

2) ANS:

body-centered cubic

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ID: A

3) ANS:

face-centered cubic

4) ANS: alloy

5) ANS: 4

PTS: 1 DIF: 3 REF: Page Ref: 12.3 OBJ: 12.3, 12.5; G2

6) ANS: 2

PTS: 1 DIF: 2 REF: Page Ref: 12.3 OBJ: 12.3, 12.5; G2

7) ANS:

silver and copper

8) ANS: band

9) ANS:

Semiconductors

10) ANS: doping

11) ANS: more

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12) ANS: quantum dots

13) ANS:

. PTS: 1 DIF: 2 REF: Page Ref: 12.8 OBJ: 12.8; G2

14) ANS:

diamine, diacid

15) ANS: copolymers

16) ANS:

crystallinity, branching

17) ANS:

Carbon nanotubes

TRUE/FALSE

1) ANS: F PTS: 1 DIF: 2 REF: Page Ref: 12.1 OBJ: 12.1; G2

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ID: A

6) ANS: T PTS: 1 DIF: 1 REF: Page Ref: 12.8 OBJ: 12.8; G2

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_____ 1)D _____ 2)E _____ 3)A _____ 4)D _____ 5)D _____ 6)B _____ 7)C _____ 8)E _____ 9)C _____ 10)C _____ 11)A _____ 12)A _____ 13)A _____ 1)F _____ 2)F _____ 3)F _____ 4)F _____ 5)F _____ 6)T