Practice Quiz 12




1.

In cubic closest packing, the unit cell is body-centered cubic.

A. True
B. False


2.

Which of the following is true about kinetic energy, Ek, and potential energy, Ep, when ethyl alcohol at 40°C is compared with ethyl alcohol at 20°C?

A.

Ek(40°C) < Ek(20°C); Ep(40°C) ≈ Ep(20°C)

B.

Ek(40°C) > Ek(20°C); Ep(40°C) ≈ Ep(20°C)

C.

Ep(40°C) < Ep(20°C); Ek(40°C) ≈ Ek(20°C)

D.

Ep(40°C) > Ep(20°C); Ek(40°C) ≈ Ek(20°C)

E.

Ep(40°C) > Ep(20°C); Ek(40°C) > Ek(20°C)



3.

The surface tension of water is lowered when a detergent is present in solution.

A. True
B. False


4.

Only molecules which do not have dipole moments can experience dispersion forces.

A. True
B. False


5.

Pentane, C5H12, boils at 35°C. Which of the following is true about kinetic energy, Ek, and potential energy, Ep, when liquid pentane at 35°C is compared with pentane vapor at 35°C?

A.

Ek(g) < Ek(l); Ep(g) ≈ Ep(l)

B.

Ek(g) > Ek(l); Ep(g) ≈ Ep(l)

C.

Ep(g) < Ep(l); Ek(g) ≈ Ek(l)

D.

Ep(g) > Ep(l); Ek(g) ≈ Ek(l)

E.

Ep(g) ≈ Ep(l); Ek(g) ≈ Ek(l)



6.

The energy of a hydrogen bond is greater than that of a typical covalent bond.

A. True
B. False


7.

When silicon is doped with an element from group 3A(13), the device/material produced is a/an

A.

intrinsic semiconductor.

B.

p-type semiconductor.

C.

n-type semiconductor.

D.

p-n junction.

E.

transistor.



8.

A metal in the simple cubic lattice will have ________________ atom(s) per unit cell.

A.

1

B.

2

C.

3

D.

4

E.

8



9.

Iron has a body-centered cubic unit cell, and a density of 7.87 g/cm3. Calculate the edge length of the unit cell, in pm. (The atomic mass of iron is 55.85 amu. Also, 1 amu = 1.661 × 10-24 g.)


Answer:


10.

Which of the following statements about the packing of monatomic solids with different unit cells is incorrect?

A.

The coordination number of atoms in hcp and fcc structures is 12.

B.

The coordination number of atoms in simple cubic structures is 6.

C.

The coordination number of atoms in bcc structures is 8.

D.

A bcc structure has a higher packing efficiency than a simple cubic structure.

E.

A bcc structure has a higher packing efficiency than a fcc structure.



11.

Which of the following factors contributes to a low viscosity for a liquid?

A.

low temperature

B.

spherical molecular shape

C.

hydrogen bonding

D.

high molecular weight

E.

high boiling point



12.

Consider the following phase diagram and identify the process occurring as one goes from point C to point D.

A.

increasing temperature with a phase change from solid to liquid

B.

increasing temperature with a phase change from solid to vapor

C.

increasing temperature with a phase change from liquid to vapor

D.

increasing temperature with no phase change

E.

increasing temperature beyond the critical point



13.

A temperature increase causes __________________ in the conductivity of a semiconductor.

A.

a decrease

B.

an increase

C.

a modulation

D.

an increase or decrease (depending on the semiconductor)

E.

no change



14.

How do the electrical properties of semiconductors differ from those of metals?


Answer:


15.

Iron crystallizes in the body-centered cubic lattice. What is the coordination number for Fe?

A.

4

B.

6

C.

8

D.

10

E.

12



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