Q: If the edge length of a cubic unit cell is $$a$$ and the unit cell contains $$n$$ atoms, which equation gives the density $$\rho of $$the solid? ($$M = $$molar mass, $$N_A = $$Avogadro's number)

$$\rho = \dfrac{n \times M}{a^3$ \times N_A}$$

Question 1

Which of the following best describes a molecular solid?

Accepted Answer

A solid composed of discrete molecules held together by intermolecular forces.

Question 2

Which technique is commonly used to determine the arrangement of atoms in crystalline solids?

Accepted Answer

X-ray crystallography

Question 3

A simple cubic unit cell contains how many atoms per unit cell?

Accepted Answer

$$1$$

Question 4

Which of the following statements about metallic solids is TRUE?

Accepted Answer

They have a sea of delocalized electrons that allows for electrical conductivity.

Question 5

Diamond and graphite are both forms of carbon. Which statement best explains why diamond is much harder than graphite?

Accepted Answer

Diamond has a network of covalent bonds in three dimensions, while graphite has layers held together by weak forces.

Question 6

Which of the following best describes the electron sea model for bonding in metals?

Accepted Answer

Valence electrons are delocalized and move freely throughout the metal lattice.

Question 7

A face-centered cubic (FCC) unit cell contains how many atoms per unit cell?

Accepted Answer

$$4$$

Question 8

Which property is most characteristic of ionic solids?

Accepted Answer

High melting points and brittleness

Question 9

Which of the following is an example of a covalent network solid?

Accepted Answer

Diamond

Question 10

If the edge length of a cubic unit cell is $$a$$ and the unit cell contains $$n$$ atoms, which equation gives the density $$\rho of $$the solid? ($$M = $$molar mass, $$N_A = $$Avogadro's number)

Accepted Answer

$$ho = \dfrac{n 	imes M}{a^3$ 	imes N_A}$$

Question 11

Which of the following best explains why ionic solids do not conduct electricity in the solid state but do when melted?

Accepted Answer

Ions are fixed in place in the solid but are free to move in the liquid.

Question 12

Which of the following is NOT a characteristic of molecular solids?

Accepted Answer

Electrical conductivity

Question 13

Which of the following statements about X-ray crystallography is correct?

Accepted Answer

It provides information about the three-dimensional structure of crystalline solids.

Question 14

Which of the following solids would you expect to have the highest melting point?

Accepted Answer

A covalent network solid such as quartz ($$\mathrm{$$SiO_2$$})$$

Question 15

Which of the following best describes the arrangement of ions in a sodium chloride ($$\mathrm{NaCl}) $$crystal?

Accepted Answer

Each sodium ion is surrounded by six chloride ions in an octahedral geometry.

Question 16

Which of the following is a property of covalent network solids but NOT of molecular solids?

Accepted Answer

High melting points

Question 17

A metal crystallizes in a body-centered cubic (BCC) structure. How many atoms are present in each unit cell?

Accepted Answer

$$2$$

Question 18

Which of the following best explains why metals are malleable and ductile?

Accepted Answer

The delocalized electrons allow metal atoms to move past each other without breaking bonds.

Question 19

Which of the following is a real-world application of X-ray crystallography?

Accepted Answer

Determining the structure of DNA

Question 20

Which of the following statements about amorphous solids is correct?

Accepted Answer

They lack long-range order in the arrangement of their particles.

Study Notes: Solids and Solid-State Materials (Chapter 12)

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