CHM 2046C: Chapter 13 - Practice Test 1

CHM 2046C Module 7II:
Chapter 13 Sample Multiple Choice Test #1 Answers

1. The correct answer is:
the vapor pressure of water will remain constant.

Explanation:
The temperature of the liquid will still be the same. Therefore, the vapor pressure of water will be the same.

Solution Reference:
Page 602

1. If heat is added to ice and liquid water in a closed container, and after the addition of the heat there is still ice and liquid water remaining

a.	the vapor pressure of water will decrease.
b.	the temperature will increase some.
c.	the temperature will decrease some.
d.	the vapor pressure of water will rise.
e.	the vapor pressure of water will remain constant.

2. The correct answer is:
N.

Explanation:
This represents an application of Dalton's law of partial pressures,

P_T = P_A + P_B ...

Solution Reference:
Page 590

2. A closed vessel contains an inert gas A at 500 mm of Hg and 60?C. What is the total pressure in mm of Hg inside the vessel after a few drops of liquid B are injected and a phase equilibrium is established at 60?C? The vapor pressure of liquid B at 60?C is 80 mm of Hg.

3. The correct answer is:
is only when the liquid and vapor are in equilibrium.

Explanation:
It is important to know the difference between boiling point and normal boiling point.

Solution Reference:
Page 605

3. The normal boiling point of a liquid

a.	is above the critical temperature.
b.	is at the triple point temperature.
c.	is at one atmosphere pressure.
d.	is usually below the triple point temperature.
e.	is only when the liquid and vapor are in equilibrium.

4. The correct answer is:
a more volatile liquid is added to the given liquid.

Explanation:
As the kinetic energy of the molecules increases, the vapor pressure must increase. The kinetic energy of the molecules is proportional to the absolute temperature.

Solution Reference:
Page 602

4. The vapor pressure of a given liquid will increase if

	a.	the liquid is moved to a container in which its surface is very much larger.
	b.	the volume of the liquid is increased.
	c.	the volume of the vapor phase is increased.
	d.	the temperature is increased.
	e.	a more volatile liquid is added to the given liquid.

5. The correct answer is:
A very low vapor pressure.

Explanation:
A high vapor pressure is an indication of weak intermolecular forces.

Solution Reference:
Page 602

5. Which of the following indicates very strong intermolecular forces of attraction in a liquid?

a.	A very low boiling point
b.	A very low critical temperature.
c.	A very low heat of vaporization.
d.	A very low vapor pressure.
e.	A very low surface tension.

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6. The correct answer is:
ICl has a measurable dipole moment and Br₂ does not.

Explanation:
ICl is a polar molecule, whereas Br₂ is a nonpolar molecule. There are dipole-dipole interactions between ICl molecules, but only dispersion forces between Br₂ molecules.

Solution Reference:
Page 588

6. The compounds Br₂ and ICl have almost identical molecular weights, yet ICl boils at 97?C and Br₂ boils at 59?C. The best explanation for the difference is

a.	ICl is an ionic compound and Br₂ is covalent.
b.	ICl is a nonpolar molecule and Br₂ is polar.
c.	ICl has a longer bond than that in Br₂.
d.	ICl has a measurable dipole moment and Br₂ does not.
e.	ICl has a stronger bond than that in Br₂.

7. The correct answer is:
N.

Solution Reference:
Page 590

7. In some compounds the hydrogen atom is covalently bonded to one atom and simultaneously attracted to another atom in another molecule by an electrostatic interaction. This interaction can occur when hydrogen is bonded to

a.	Cl.
b.	Si.
c.	N.
d.	C.
e.	Br.

8. The correct answer is:
CH₃CH₂CH₂F

Solution Reference:
Page 590

8. Which of the following compounds would be expected to have the lowest boiling point?

a.	CH₃CH₂CH₂F
b.	CH₃CH₂CH₂OH
c.
d.	CH₃CH₂COOH
e.	CH₃CH₂CH₂NH₂

9. The correct answer is:
CH₃CH₂CH₂Br

Solution Reference:
Page 595

9. Which of the following compounds is expected to have the highest boiling point?

a.	CH₃CH₃
b.	CH₃CH₂CH₃
c.	CH₃OCH₃
d.	CH₃CH₂CH₂Cl
e.	CH₃CH₂CH₂Br

10. The correct answer is:
H₂O

Solution Reference:
page 599

10. Which of the following would be expected to have the highest heat of vaporization?

a.	H₂O
b.	NH₃
c.	PH₃
d.	AsH₃
e.	SbH₃

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11. The correct answer is:
M, N, O: M = solid, N = liquid, O = gas

Explanation:
N represents the solid area, O represents the liquid area, and M the gaseous area.

Solution Reference:
Page 629, Phase Diagrams

11. In the phase diagram below, the solid, liquid, and vapor phases are represented respectively by

a.	O, M, N.
b.	O, N, M. O, N, M.
c.	N, O, M.
d.	N, M, O.
e.	M, N, O.

12. The correct answer is:
solidification.

Explanation:
Point N is in the solid state and Point M is in the liquid state.

Solution Reference:
Page 629, Phase Diagrams

12. From a consideration of the phase diagram below, a change from point M to point N corresponds to

a.	sublimation.
b.	condensation.
c.	evaporation.
d.	solidification.
e.	liquefaction.

13. The correct answer is:

a physical change

13. The sublimation of solid carbon dioxide, dry ice, is an example of

a.	evaporation.
b.	a physical property.
c.	a chemical property.
d.	a chemical change.
e.	a physical change.

14. The correct answer is:
heat of fusion plus heat of vaporization.

Explanation:

Solution Reference:
Page 625, The Physical Properties of Solids

14. The heat of sublimation of a compound equals

a.	heat of fusion plus heat of vaporization.
b.	heat of ionization plus heat of crystallization.
c.	heat of vaporization minus heat of fusion.
d.	heat of vaporization plus heat of crystallization.
e.	heat of crystallization minus heat of vaporization.

15. The correct answer is:

The triple point must be less than 178^oC

15. The critical point of carbon tetrachloride is 283^oC and 45 atm pressure. Liquid carbon tetrachloride has a vapor pressure of 10.0 atm at 178^oC. Which of the following statements must be true?

a.	The normal boiling of CCl₄ must be greater than 178^oC.
b.	Liquid CCl₄ can exist at temperatures greater than 283^oC if the pressure is greater than 45 atm.
c.	The triple point must be less than 178^oC.
d.	Liquid and solid can only be in equilibrium at one temperature -- the freezing point.
e.	Vapor and liquid can only be in equilibrium at one temperature -- the normal boiling point.

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16. The correct answer is:
CH₄

Explanation:
Graphite, diamond and SiO₂ are giant molecules. Sodium chloride has a crystalline lattice that consists of an infinite array of ions. Methane molecules in the solid state are held together by weak dispersion forces.

Solution Reference:
Page 621

16. Which of the following as solids has a crystal containing discrete (or separate) molecules?

a.	NaCl
b.	CH₄
c.	graphite
d.	diamond
e.	SiO₂

17. The correct answer is:
MgCl₂

Explanation:
In this question, we only need to consider LiCl and MgCl₂ because CCl₄, NCl₃, and OCl₂ are covalent compounds. The ionic compound (LiCl or MgCl₂) with the higher melting point will be the one with the larger crystal lattice energy.

where z⁺ and z^- are the charges on the positive ions and negative ions respectively and r_o is the distance that they are separated. The smaller the ions, the smaller r_o will be and the higher U will be. M is a geometric factor that is characteristic for different types of crystals.

Solution Reference:
Page 609

17. Which of the following compounds would be expected to have the highest melting point?

a.	LiCl
b.	CCl₄
c.	MgCl₂
d.	NCl₃
e.	OCl₂

18. The correct answer is:
a corner atom.

Explanation:
An edge atom is shared between four unit cells. A face atom is shared between two unit cells. A body-centered atom is shared by one unit cell.

Solution Reference:
Page 610

18. An atom that is shared equally between eight cubic unit cells is called

a.	a corner atom.
b.	a face atom.
c.	a body-centered atom.
d.	an edge atom.
e.	a diagonal atom.

19. The correct answer is:
2

Explanation:
# atoms = 8 x 1/8 + 1 x 1 = 2

Solution Reference:
Page 610

19. Europium crystallizes in a body-centered cubic lattice. The number of europium atoms in a unit cell is

a.	1
b.	2
c.	4
d.	6
e.	8

20. The correct answer is:
M²⁺ ions at the corners and at each face, 8 X^- ions at the body centers.

Explanation:
# M²⁺ = 8 x 1/8 + 6 x 1/2 = 4 # X^- = 8 x 1 = 8 MX₂

Solution Reference:
Page 610

20. An ionic crystalline solid, MX₂, has cubic unit cell. Which of the following arrangements of the ions is consistent with the stoichiometry of the compound?

a.	M²⁺ ions at the corners and at each face, 8 X^- ions at the body centers.
b.	M²⁺ ions at each face, X^- ions at the corners.
c.	M²⁺ ions at the corners, X^- ions at the faces and 2 X^- ions at the body centers.
d.	4 M²⁺ ions at the body centers, X^- ions at the corners and at the face centers.
e.	M²⁺ ions at the corners and at the face centers, 4 X^- ions at the body centers.

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21. The correct answer is:
12

Explanation:

Solution Reference:
Page 610

21. In UO₂, the uranium ions form a face-centered cubic lattice. The oxide ions occupy the tetrahedral sites. The uranium ions occupy the faces and comers of the unit cell. The total number of uranium ions and oxide ions per unit cell is

a.	2
b.	4
c.	6
d.	8
e.	12

Question Instructions: Lithium chloride crystallizes in a face-centered cubic structure. The unit cell length is 5.14 x 10^-8 cm. The chloride ions are touching each other along the face diagonal of the unit cell. The lithium ions fit into the holes between the chloride ions.

22. The correct answer is:
4

Explanation:

Solution Reference:
Page 610

22. How many lithium ions are there in this unit cell?

a.	1
b.	2
c.	3
d.	4
e.	8

23. The correct answer is:
2.82 x 10^-22 g

Explanation:

Solution Reference:
Page 610

23. What is the mass of LiCl in a unit cell?

a.	7.04 x 10^-23 g
b.	1.41 x 10^-22 g
c.	2.82 x 10^-22 g
d.	4.22 x 10^-22 g
e.	5.63 x 10^-22 g

24. The correct answer is:
2.08 g/cc

Explanation:

Solution Reference:
Page 610

24. What is the density of the lithium chloride?

a.	1.04 g/cc
b.	2.08 g/cc
c.	2.42 g/cc
d.	3.11 g/cc
e.	3.78 g/cc

25. The correct answer is:
1.82 x 10^-8 cm

Explanation:
The face diagonal corresponds to four chloride ion radii. Why?

Solution Reference:
Page 610

25. What is the radius of the chloride ion?

a.	1.29 x 10^-8 cm
b.	1.82 x 10^-8 cm
c.	2.23 x 10^-8 cm
d.	2.56 x 10^-8 cm
e.	2.76 x 10^-8 cm

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