Q: A sample of aluminum crystallizes in a face-centered cubic unit cell with an atomic radius of 143 pm. What is the edge length $l$ of the unit cell in meters?

$l = 2\sqrt{2} \times 143 \times 10^{-12}$ m

Question 1

Which of the following statements best describes the difference between molecular solids and ionic solids?

Accepted Answer

Molecular solids are composed of molecules held together by intermolecular forces, while ionic solids are composed of ions held together by coulombic forces.

Question 2

A body-centered cubic unit cell has an edge length $l$. What is the relationship between the edge length $l$ and the atomic radius $r$?

Accepted Answer

$l = \frac{4r}{\sqrt{3}}$

Question 3

Which type of atomic solid is most likely to have the lowest melting point?

Accepted Answer

Nonbonding atomic solid

Question 4

How many atoms are present in a face-centered cubic unit cell?

Accepted Answer

4

Question 5

Which property of graphite allows it to be used as a lubricant?

Accepted Answer

Slippery feel due to weak dispersion forces between sheets

Question 6

A sample of aluminum crystallizes in a face-centered cubic unit cell with an atomic radius of 143 pm. What is the edge length $l$ of the unit cell in meters?

Accepted Answer

$l = 2\sqrt{2} 	imes 143 	imes 10^{-12}$ m

Question 7

Which of the following best explains why ionic solids generally have higher melting points than molecular solids?

Accepted Answer

Ionic solids are held together by strong coulombic forces between ions.

Question 8

What is the packing efficiency of a face-centered cubic unit cell?

Accepted Answer

74%

Question 9

Which type of polymerization involves the elimination of a small molecule, such as water, during the formation of the polymer?

Accepted Answer

Condensation polymerization

Question 10

A body-centered cubic unit cell has a volume of $4.32 	imes 10^{-23}$ cm$^3$. What is the atomic radius $r$ in pm?

Accepted Answer

152 pm

Question 11

Which of the following is a network covalent atomic solid?

Accepted Answer

Quartz (SiO$_2$)

Question 12

Which of the following statements about diamond is true?

Accepted Answer

Diamond is held together by covalent bonds in a tetrahedral geometry.

Question 13

What is the coordination number of a simple cubic unit cell?

Accepted Answer

6

Question 14

Which of the following is a real-world application of polymers produced by addition polymerization?

Accepted Answer

Pipe fittings made from polyvinyl chloride (PVC)

Question 15

Which of the following best describes the structure of graphite?

Accepted Answer

Carbon atoms are arranged in flat sheets of fused six-membered rings held together by dispersion forces.

Question 16

Which equation would you use to calculate the density $d$ of a crystalline solid given the mass $m$ and volume $V$ of the unit cell?

Accepted Answer

$d = \frac{m}{V}$

Question 17

Which of the following statements about metallic atomic solids is correct?

Accepted Answer

They are held together by metallic bonds and have variable melting points.

Question 18

Which of the following is a copolymer?

Accepted Answer

A polymer made from two different kinds of monomers

Question 19

Which of the following best explains why the coordination number affects the stability of an ionic solid?

Accepted Answer

A higher coordination number increases the number of cation–anion interactions, lowering the potential energy of the solid.

Question 20

Which of the following is true about the packing efficiency of unit cells?

Accepted Answer

Face-centered cubic unit cells have the highest packing efficiency among the cubic types.

Solids and Modern Materials: Structure, Types, and Properties

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