Question 1

Identify the solid that has a high melting point, is hard and brittle, and conducts electricity when liquefied.

Accepted Answer

A)  a network covalent solid
B)  a metal
C)  a covalent network
D)  an ionic solid
E)  an amorphous solid D

Question 2

In a simple cubic unit cell there is/are ________ atom(s), in a face-centered cubic cell there is/are ________ atom(s), and in a body-centered cubic cell there is/are ________ atom(s).

Accepted Answer

1; 4; 2

Question 3

Which of these materials is the best conductor of electricity?

Accepted Answer

A)  diamond
B)  graphite
C)  water
D)  glass
E)  fullerene B

Question 4

Define the term allotrope, name the two most common allotropes of carbon, and provide a brief description of their structure.

Accepted Answer

The answer of Define the term allotrope, name the two...

Question 5

Which of the following can be varied to change the physical properties of an alloy?
I.the elements used
II.the proportions used
III.the type of hole each element occupies

Accepted Answer

A)  I only
B)  II only
C)  III only
D)  I and II only
E)  I, II, and III

Question 6

Different structural forms of the elements are called ________

Accepted Answer

A)  polymers.
B)  allotropes.
C)  isotopes.
D)  isoforms.
E)  polymorphs.

Question 7

Potassium bromide crystallizes in the rock salt structure. It has a density of 2.75 g/cm3. What is the edge length of the unit cell? In the rock salt structure, the bromide ions form an fcc unit cell, and the potassium ions occupy the octahedral holes.

Accepted Answer

A)  220 pm
B)  330 pm
C)  440 pm
D)  550 pm
E)  660 pm

Question 8

What is the likely unit cell for ionic compounds of 1:1 stoichiometry in which the difference in the radii is only about 25% or less?

Accepted Answer

A)  rock salt
B)  sphalerite
C)  fluorite
D)  cubic
E)  antifluorite

Question 9

Which of the following shows a small section of polyethylene?

Accepted Answer

A)   
B)   
C)   
D)   
E)

Question 10

An atom in a particular unit cell has 8 nearest neighbor atoms around it. Which unit cell(s) are possible?

Accepted Answer

A)  simple cubic
B)  body-centered cubic
C)  face-centered cubic
D)  hexagonal
E)  face-centered cubic or hexagonal

Question 11

The cubic closest-packed crystal structure has a ________ layering pattern that produces a ________ unit cell. The hexagonal closest-packed crystal structure has a ________ layering pattern that produces a ________ unit cell.

Accepted Answer

The answer of The cubic closest-packed crystal structure has a...

Question 12

Which statement A-D does not describe a simple cubic unit cell?

Accepted Answer

A)  It results from square packing of atoms in layers.
B)  The atoms lie at the corners of a cube.
C)  Each atom has 6 nearest neighbors.
D)  The stacking pattern can be represented by aaaa.
E)  Statements A-D all correctly describe a simple cubic unit cell.

Question 13

As an analog of graphite, a material composed of boron and nitrogen (B-N) has been prepared. Why do these elements make a good substitute for the element in graphite?
I.They are all elements with electrons in the 2p subshell.
II.The sum of the valence electrons of one boron atom and one nitrogen atom is the same as the number of valence electrons on two carbon atoms.
III.Boron and nitrogen have suitable 2p orbital overlap.

Accepted Answer

A)  I only
B)  II only
C)  III only
D)  I and II only
E)  I, II, and III

Question 14

A hexagonal closest-packed structure has hexagonally arranged layers of atoms stacking in the series ________

Accepted Answer

A)  ababab
B)  abcabcabc.
C)  abcbabcbabcba.
D)  abacabacaba.
E)  aaaaaa.

Question 15

How many nearest neighbor atoms are there around each atom in a face-centered cubic unit cell?

Accepted Answer

A)  4
B)  6
C)  8
D)  10
E)  12

Question 16

Aluminum (Al) has a density of 2.70 g/cm3 and crystallizes in a face-centered cubic structure. What is the unit cell edge length?

Accepted Answer

A)  2.47  10-3 pm
B)  40.0 pm
C)  405 pm
D)  321 pm
E)  255 pm

Question 17

Polyethylene terephthalate, or Dacron, is a polymer commonly found in food and beverage containers. Dacron is prepared by reaction of terephthalic acid and ethylene glycol, shown below. What type of reaction is this?

Accepted Answer

A)  chiral polymerization
B)  condensation polymerization
C)  metathesis polymerization
D)  addition polymerization
E)  olefin polymerization

Question 18

A homopolymer is a polymer in which ________

Accepted Answer

A)  each polymer has the same mass.
B)  each polymer has the same mass and structure.
C)  the monomers are distributed uniformly throughout the polymer.
D)  the polymers are distributed uniformly throughout the solution.
E)  there is only one monomer unit.

Question 19

The face-centered cubic structure is also known as ________

Accepted Answer

A)  cubic closest-packed.
B)  hexagonal closest-packed.
C)  square closest-packed.
D)  spherical closest-packed.
E)  none of the above, as it is not a closest-packed pattern.

Question 20

The closest-packing of spheres (such as oranges, cannonballs, or atoms) has the spheres ________

Accepted Answer

A)  arranged in layers with each sphere surrounded by 4 other spheres in the layer.
B)  arranged in layers with each sphere surrounded by 3 other spheres in the layer.
C)  arranged in a square pattern with a sphere at each corner and one in the center of the square.
D)  arranged in a square pattern with a sphere at each corner of the square.
E)  arranged in layers with each sphere surrounded by 6 other spheres in the layer.

Exam 12: Solids: Crystals, Alloys, and Polymers