chemistry

Chapter 12 Intermolecular Forces: Liquids, Solids, and Phase Changes

Student: ______________________________________________________________________

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

2. Which of the following is true about kinetic energy, Ek, and potential energy, Ep, when ethyl

alcohol at 40C is compared with ethyl alcohol at 20C? A. Ek(40C) < Ek(20C); Ep(40C) Ep(20C)B. Ek(40C) > Ek(20C); Ep(40C) Ep(20C)C. Ep(40C) < Ep(20C); Ek(40C) Ek(20C)D. Ep(40C) > Ep(20C); Ek(40C) Ek(20C)E. Ep(40C) > Ep(20C); Ek(40C) > Ek(20C)

3. A sample of octane in equilibrium with its vapor in a closed 1.0-L container has a vapor

pressure of 50.0 torr at 45C. The container's volume is increased to 2.0 L at constant temperature and the liquid/vapor equilibrium is reestablished. What is the vapor pressure? A. > 50.0 torrB. 50.0 torrC. 25.0 torrD. The mass of the octane vapor is needed to calculate the vapor pressure.E. The external pressure is needed to calculate the vapor pressure.

4. Which one of the following quantities is generally not obtainable from a single heating or

cooling curve of a substance, measured at atmospheric pressure? A. melting pointB. boiling pointC. triple pointD. heat of fusionE. heat of vaporization

5. The phase diagram for xenon has a solid-liquid curve with a positive slope. Which of the following is true? A. Solid xenon has a higher density than liquid xenon.B. Solid xenon has the same density as liquid xenon.C. The phase diagram cannot be used to predict which phase of xenon is denser.D. Freezing xenon is an endothermic process.E. None of these choices is correct.

6. Liquid ammonia (boiling point = -33.4C) can be used as a refrigerant and heat transfer

fluid. How much energy is needed to heat 25.0 g of NH3(l) from -65.0C to -12.0C?Specific heat capacity, NH3(l) : 4.7 J/(g ∙ K)Specific heat capacity, NH3(g): 2.2 J/(g ∙ K)Heat of vaporization: 23.5 kJ/molMolar mass, м: 17.0 g/mol A. 5.5 kJB. 6.3 kJC. 39 kJD. 340 kJE. 590 kJ

7. Diethyl ether, used as a solvent for extraction of organic compounds from aqueous

solutions, has a high vapor pressure which makes it a potential fire hazard in laboratories in which it is used. How much energy is released when 100.0 g is cooled from 53.0C to 10.0C?Boiling point: 34.5CHeat of vaporization: 351 J/gSpecific heat capacity, (CH3)2O(l): 3.74 J/(g ∙ K)Specific heat capacity, (CH3)2O(g): 2.35 J/(g ∙ K) A. 10.1 kJB. 13.1 kJC. 16.1 kJD. 45.2 kJE. 48.6 kJ

8. A 5.00 g sample of water vapor, initially at 155C is cooled at atmospheric pressure,

producing ice at -55C. Calculate the amount of heat energy lost by the water sample in this process, in kJ. Use the following data: specific heat capacity of ice is 2.09 J/g ∙ K; specific heat capacity of liquid water is 4.18 J/g ∙ K; specific heat capacity of water vapor is 1.84 J/g ∙ K; heat of fusion of ice is 336 J/g; heat of vaporization of water is 2260 J/g. A. 15.6 kJB. 10.2 kJC. 5.4 kJD. 3.2 kJE. 1.6 kJ

9. Octane has a vapor pressure of 40. torr at 45.1C and 400. torr at 104.0C. What is its heat of vaporization? A. 39.0 kJ/molB. 46.0 kJ/molC. 590 kJ/molD. 710 kJ/molE. None of these choices is correct.

10. Liquid sodium can be used as a heat transfer fluid. Its vapor pressure is 40.0 torr at 633C

and 400.0 torr at 823C. Calculate its heat of vaporization. A. 43.4 kJ/molB. 52.5 kJ/molC. 70.6 kJ/molD. 1.00 102 kJ/molE. None of these choices is correct.

11. The Clausius-Clapeyron equation is used in calculations of

A. melting and freezing points.B. vapor pressures of liquids.C. osmotic pressures of solutions.D. heats of vaporization at different temperatures.E. crystal structure.

12. The normal boiling point of ether is 307.8 K. Calculate the temperature at which its vapor

pressure is exactly half of that at its normal boiling point. The heat of vaporization for ether is 26.69 kJ/mol. A. 305 KB. 302 KC. 295 KD. 289 KE. 281 K

13. Examine the phase diagram for the substance Bogusium (Bo) and select the correct statement.

A. Bo(s) has a lower density than Bo(l).B. The triple point for Bo is at a higher temperature than the melting point for Bo.C. Bo changes from a solid to a liquid as one follows the line from C to D.D. Bo changes from a liquid to a gas as one follows the line from C to D.E. Point B represents the critical temperature and pressure for Bo.

14. Examine the following phase diagram and identify the feature represented by point A.

A. melting pointB. critical pointC. triple pointD. sublimation pointE. boiling point

15. Examine the following phase diagram and identify the feature represented by point B.

A. melting pointB. triple pointC. critical pointD. sublimation pointE. boiling point

16. 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 liquidB. increasing temperature with a phase change from solid to vaporC. increasing temperature with a phase change from liquid to vaporD. increasing temperature with no phase changeE. increasing temperature beyond the critical point

17. Examine the following phase diagram and determine what phase exists at point F.

A. vapor + liquidB. vaporC. liquidD. solidE. supercritical fluid

18. Neon atoms are attracted to each other by

A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. covalent bonding.E. intramolecular forces.

19. Ammonia's unusually high melting point is the result of

A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. covalent bonding.E. ionic bonding.

20. Octane is a component of fuel used in internal combustion engines. The dominant

intermolecular forces in octane are A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. covalent bonds.E. carbon-hydrogen bonds.

21. In hydrogen iodide __________________ are the most important intermolecular forces. A. dipole-dipole forcesB. London dispersion forcesC. hydrogen bondingD. covalent bondsE. polar covalent bonds

22. When the electron cloud of a molecule is easily distorted, the molecule has a high

_____________. A. polarityB. polarizabilityC. dipole momentD. van der Waals radiusE. compressibility

23. Which of the following atoms should have the greatest polarizability?

A. FB. BrC. PoD. PbE. He

24. Which of the following atoms should have the smallest polarizability?

A. SiB. SC. TeD. BiE. Br

25. The strongest intermolecular interactions between pentane (C5H12) molecules arise from

A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. ion-dipole interactions.E. carbon-carbon bonds.

26. What types of forces exist between molecules of CO2? A. hydrogen bonding only.B. hydrogen bonding and dispersion forces.C. dipole-dipole forces only.D. dispersion forces only.

27. The strongest intermolecular interactions between ethyl alcohol (CH3CH2OH) molecules arise from A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. ion-dipole interactions.E. carbon-oxygen bonds.

28. The strongest intermolecular interactions between hydrogen sulfide (H2S) molecules arise

from A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. ion-dipole interactions.E. disulfide linkages.

29. The strongest intermolecular interactions between hydrogen fluoride (HF) molecules arise

from A. dipole-dipole forces.B. London dispersion forces.C. hydrogen bonding.D. ion-dipole interactions.E. ionic bonds.

30. Which one of the following substances will have hydrogen bonds between molecules?

A. (CH3)3NB. CH3 O CH3

C. CH3CH2 OHD. CH3CH2 FE. HI

31. In which of the following compounds will the molecules not form hydrogen bonds with each other?

A.B.

C.

D.E.

32. Which of the following pairs of molecules can form hydrogen bonds between them?

A. HCl and HIB. CH3OH and NH3

C. CH4 and H2OD. SO2 and CH2OE. H2 and O2

33. Which of the following pairs is arranged with the particle of higher polarizability listed

first? A. Se2-, S2-

B. I, I-

C. Mg2+, MgD. Br, IE. None of these choices is correct.

34. Which of the following pairs is arranged with the particle of higher polarizability listed

first? A. CCl4, CI4

B. H2O, H2SeC. C6H14, C4H10

D. NH3, NF3

E. None of these choices is correct. 35. Which of the following should have the highest boiling point?

A. CF4

B. CCl4

C. CBr4

D. CI4

E. CH4

36. Which of the following should have the lowest boiling point? A. C5H12

B. C6H14

C. C8H18

D. C10H22

E. C12H26 37. Which of the following has a boiling point which does not fit the general trend?

A. NH3

B. PH3

C. AsH3

D. SbH3

E. BiH3 38. Select the pair of substances in which the one with the higher vapor pressure at a given

temperature is listed first. A. C7H16, C5H12

B. CCl4, CBr4

C. H2O, H2SD. CH3CH2OH, CH3 O CH3

E. Xe, Kr 39. Select the pair of substances in which the one with the lower vapor pressure at a given

temperature is listed first.

A. and CH3CH2CH2OHB. PH3 and NH3

C. CF4 and CBr4

D. C3H8 and C4H10

E. F2 and Cl2 40. Comparing the energies of the following intermolecular forces on a kJ/mol basis, which

would normally have the highest energy (i.e., be the strongest force)? A. ion-induced dipoleB. dipole-induced dipoleC. ion-dipoleD. dipole-dipoleE. dispersion

41. Which of the following should have the highest surface tension at a given temperature?

A. CH4

B. CF4

C. CCl4

D. CBr4

E. CI4

42. Which of the following should have the highest surface tension at a given temperature? A.B.

C.

D.E.

43. Which of the following properties measures the energy needed to increase the surface area

of a liquid? A. capillary actionB. surface tensionC. viscosityD. cohesionE. specific elasticity

44. When the adhesive forces between a liquid and the walls of a capillary tube are greater than

the cohesive forces within the liquid A. the liquid level in a capillary tube will rise above the surrounding liquid and the

surface in the capillary tube will have a convex meniscus.B. the liquid level in a capillary tube will rise above the surrounding liquid and the

surface in the capillary tube will have a concave meniscus.C. the liquid level in a capillary tube will drop below the surrounding liquid and the

surface in the capillary tube will have a convex meniscus.D. the liquid level in a capillary tube will drop below the surrounding liquid and the

surface in the capillary tube will have a concave meniscus.E. None of these choices is correct.

45. The meniscus of mercury in a glass capillary tube is convex because of

A. the very high density of mercury as compared with water.B. the low surface tension of mercury.C. the greater attraction of mercury atoms to the glass than to each other.D. the weaker attraction of mercury atoms to the glass than to each other.E. electrostatic repulsion between the glass and the mercury.

46. Which of the following terms refers to the resistance of a liquid to flow?

A. surface tensionB. capillary actionC. viscosityD. adhesionE. cohesion

47. Which of the following factors contributes to a low viscosity for a liquid? A. low temperatureB. spherical molecular shapeC. hydrogen bondingD. high molecular weightE. high boiling point

48. Which of the following pairs of substances is arranged so that the one with higher viscosity

is listed first?

A.

B.

C.

D.E. None of these choices is correct.

49. Which of the following liquid substances would you expect to have the lowest surface

tension? A. PbB. CH3OCH3

C. HOCH2CH2OHD. H2OE. CH3CH2OH

50. Which of the following liquids is likely to have the highest surface tension?

A. Br2

B. C8H18

C. CH3OCH3

D. CH3OHE. Pb

51. When identical particles pack in a simple cubic lattice, there is/are ____ particle(s) per unit

cell. A. 1B. 2C. 3D. 4E. 8

52. A metal with a body-centered cubic lattice will have ______ atom(s) per unit cell. A. 1B. 2C. 3D. 4E. 9

53. A metal such with a face-centered cubic lattice will have ________________ atom(s) per

unit cell. A. 1B. 2C. 3D. 4E. 10

54. Polonium crystallizes in the simple cubic lattice. What is the coordination number for Po?

A. 3B. 4C. 6D. 8E. 12

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

Fe? A. 4B. 6C. 8D. 10E. 12

56. Lead crystallizes in the face-centered cubic lattice. What is the coordination number for

Pb? A. 4B. 6C. 8D. 10E. 12

57. Which one of the following statements about unit cells and packing in solids is incorrect?

A. In any unit cell of a solid crystal, each face of the cell must have an opposite face which is equal and parallel to it.

B. The faces of a unit cell must all be at angles of 90 to each other.C. The coordination number of atoms in a close packed metal is 12.D. The packing efficiency in fcc structures is higher than in bcc structures.E. The packing efficiency in fcc and hcp structures is the same.

58. Which of the following statements concerning a face-centered cubic unit cell and the corresponding lattice, made up of identical atoms, is incorrect? A. The coordination number of the atoms in the lattice is 8.B. The packing in this lattice is more efficient than for a body-centered cubic system.

C. If the atoms have radius r, then the length of the cube edge is r.D. There are four atoms per unit cell in this type of packing.E. The packing efficiency in this lattice and hexagonal close packing are the same.

59. 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.

60. A cubic unit cell has an edge length of 400. pm. The length of its body diagonal (internal

diagonal) in pm is therefore: A. 512B. 566C. 631D. 693E. 724

61. A certain solid metallic element has a density 7.87 g/cm3 and a molar mass of 55.85 g/mol.

It crystallizes with a cubic unit cell, with an edge length of 286.7 pm. Calculate the number of atoms per unit cell. A. 1B. 2C. 3D. 4E. 6

62. Crystal structures may be conveniently measured using

A. X-ray diffraction.B. infrared spectroscopy.C. ultraviolet-visible spectroscopy.D. microwave spectroscopy.E. magnetic resonance imaging.

63. Which one of the following substances does not exist in the indicated solid type?

A. graphite - networkB. Na - metallicC. SiO2 - molecularD. NaCl - ionicE. diamond - network

64. When liquid bromine is cooled to form a solid, which of the following types of solid would it form? A. atomicB. metallicC. molecularD. ionicE. covalent network

65. For the solid forms of the following elements, which one is most likely to be of the

molecular type? A. XeB. CC. PbD. SE. Cr

66. What adjective best describes the solid compound IF7?

A. metallicB. amorphousC. covalent networkD. molecularE. ionic

67. The coordination number of sodium and chloride ions in the NaCl lattice, are, respectively:

A. 10 and 10B. 8 and 8C. 6 and 6D. 4 and 4E. None of these choices is correct.

68. In an ionic solid MX consisting of the monatomic ions, M+ and X-, the coordination number

of M+ is ___. A. 1B. 2C. 6D. 8E. impossible to predict without knowing the crystal structure of MX

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

semiconductor. A. a decreaseB. an increaseC. a modulationD. an increase or decrease (depending on the semiconductor)E. no change

70. A temperature increase causes __________________ in the conductivity of a conductor. A. a decreaseB. an increaseC. an increase or decrease (depending on the conductor)D. a modulationE. no change

71. The energy gap between the conduction band and the valence band is large for

A. conductors.B. semiconductors.C. superconductors.D. insulators.E. alloys.

72. The highest temperature at which superconductivity has been achieved is approximately:

A. 4 KB. 30 KC. 70 KD. 100 KE. 130 K

73. 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.

74. What word best describes the type of liquid crystal represented in this figure?

A. nematicB. cholestericC. smecticD. isotropicE. elastic

75. Which of the following statements about ceramics is incorrect? A. Silicon carbide has a diamond-like structure.B. Boron nitride can exist in both diamond-like and graphite-like forms.C. Silicon carbide can be prepared by direct reaction of silicon and carbon.D. Superconducting ceramics present manufacturing difficulties owing to their

brittleness.E. Superconducting ceramic compounds usually incorporate cobalt in a key role.

76. Mercury melts at -39C and boils at 357C. Draw a diagram of the heating curve of

mercury. Label all lines and axes, and clearly indicate the melting and boiling points on your diagram.

77. Consider the phase diagram shown below.

a. What phase(s) is/are present at point A?b. What phase(s) is/are present at point B?c. Name point C and explain its significance.d. Starting at D, if the pressure is lowered while the temperature remains constant, describe what will happen.

78. Draw a fully labeled phase diagram (P versus T) of a substance whose solid phase can melt due to applied pressure (i.e., solid is less dense than liquid). Clearly label the triple point and the critical temperature on your diagram.

79. Liquid ammonia boils at -33.4C and has a heat of vaporization of 23.5 kJ/mol. Calculate its

vapor pressure at -50.0C.

80. Chlorine trifluoride is used in processing nuclear reactor fuel. It has a vapor pressure of

29.1 torr at -47.0C and its heat of vaporization is 30.61 kJ/mol. At what temperature would its vapor pressure be 107.7 torr?

81. The vapor pressure of 1-butene is 1.268 atm at 273.15 K and its heat of vaporization is 22.9

kJ/mol. What is the normal boiling point of 1-butene?

82. a. State the essential requirements for hydrogen bonding to be important in a compound.

b. List four properties of water which are significantly influenced by the presence of hydrogen bonding.

83. a. Explain what is meant by the term "unit cell."b. Copper metal has a face-centered cubic unit cell. The edge length of the unit cell is 361 pm, and the atomic weight of copper is 63.55 amu. Calculate the density of the copper in g/cm3.(1 amu = 1.661 10-24 g.)c. From the data in (b), calculate the radius of a copper atom in pm.

84. Strontium metal crystallizes in a cubic unit cell which has an edge length of 612 pm. If the

mass of an atom of Sr is 87.62 amu, and the density of Sr metal is 2.54 g/cm3, calculate the number of atoms per unit cell. (1 amu = 1.661 10-24 g.)

85. 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 10-24g.)

86. Assuming that atoms are spherical, calculate the fraction of space which is occupied by

atoms (i.e., the packing efficiency) in a metal with a simple cubic unit cell.

87. Assuming that atoms are spherical, calculate the fraction of space which is occupied by atoms (i.e., the packing efficiency) in a metal with a face-centered cubic unit cell.

88. a. Name the two unit cells which occur in close packing of identical atoms.

b. Briefly explain how the two types of close-packed lattices of identical atoms differ, in terms of atomic arrangements.

89. Of the five major types of crystalline solid, which would you expect each of the following

to form? (e.g., H2O: molecular)a. Snb. Sic. KCld. Xee. F2

90. The density of solid sodium chloride, NaCl, is 2.17 g/cm3. Use your knowledge of the

sodium chloride lattice to calculate the spacing between Na+ and Cl- nearest neighbors, in cm.(Atomic masses (amu) are: Na, 22.99; Cl, 35.45. Also, 1 amu = 1.661 10-24 g)

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

92. Use molecular orbital band diagrams to explain why metals are good conductors but

semiconductors are not.

93. Germanium is a semiconductor. With the aid of diagrams showing bands of molecular

orbital, explain why it is a poor conductor and how doping it with phosphorus increases its conductivity.

94. List the three common classes of liquid crystals in order of decreasing degree of order.

95. The maximum number of phases of a single substance which can coexist in equilibrium is

two. Difficulty: M True False

96. The phase diagram of a substance shows the energy changes associated with changes of

state. Difficulty: E True False

97. Some of the information obtained from the heating or cooling curve of a substance can also

be found on a phase diagram of that substance. Difficulty: E True False

98. The phase diagram of a substance can be used to obtain the vapor pressure of that substance at a given temperature. Difficulty: M True False

99. All gases can be liquefied at room temperature simply by increasing the pressure on the gas.

Difficulty: E True False

100. If the solid form of a pure substance is denser than its liquid form, an increase in pressure

will cause the melting point to decrease. Difficulty: E True False

101. A liquid may be made to boil at room temperature, simply be lowering the pressure.


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

Difficulty: M True False

103. A single water molecule can participate in at most two hydrogen bonds at any instant.


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


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


106. In the packing of identical atoms with cubic unit cells, the packing efficiency increases as

the coordination number increases. Difficulty: M True False

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


108. Hexagonal close packing of identical atoms occurs when close-packed layers are stacked in

an abcabc.... arrangement. Difficulty: M True False

109. In metals, the conduction bands and valence bands of the molecular orbitals are separated by a large energy gap. Difficulty: E True False

110. In a transistor, the current through one semiconductor junction controls the current through

a neighboring junction. Difficulty: E True False

111. Liquid crystal displays are most commonly constructed of smectic type liquid crystals.


112. Smectic liquid crystals are more highly ordered than either nematic or cholesteric liquid

crystals. Difficulty: M True False

113. Ceramic superconductors often contain copper in unusual oxidation states.


Chapter 12 Intermolecular Forces: Liquids, Solids, and Phase Changes Key1. (p. 441) D 2. (p. 442) B 3. (p. 446) B 4. (p. 448) C 5. (p. 448) A 6. (Sec. 12.2) C 7. (Sec. 12.2) E 8. (Sec. 12.2) A 9. (p. 446) A 10. (p. 446) D 11. (p. 446) B 12. (p. 446) D 13. (p. 448) E 14. (p. 448) C 15. (p. 448) C 16. (p. 448) B 17. (p. 448) B 18. (p. 454) B 19. (p. 452) C 20. (p. 454) B 21. (p. 451) A 22. (p. 454) B 23. (p. 454) D 24. (p. 454) B 25. (p. 454) B 26. (p. 454) E 27. (p. 454) C 28. (p. 451) A

29. (p. 452) C 30. (p. 452) C 31. (p. 452) C 32. (p. 452) B 33. (p. 454) A 34. (p. 454) C 35. (p. 455) D 36. (p. 455) A 37. (p. 453) A 38. (p. 455) B 39. (p. 455) A 40. (Sec. 12.3) C 41. (p. 457) E 42. (p. 457) D 43. (p. 457) B 44. (p. 458) B 45. (p. 458) C 46. (p. 458) C 47. (p. 458) B 48. (p. 458) B 49. (p. 457) B 50. (p. 457) E 51. (p. 465) A 52. (p. 465) B 53. (p. 465) D 54. (p. 465) C 55. (p. 465) C 56. (p. 465) E 57. (Sec. 12.6) B 58. (Sec. 12.6) A 59. (Sec. 12.6) E

60. (Sec. 12.6) D 61. (Sec. 12.6) B 62. (p. 468) A 63. (p. 470) C 64. (p. 470) C 65. (p. 470) D 66. (p. 470) D 67. (p. 471) C 68. (Sec. 12.6) E 69. (p. 475) B 70. (p. 475) A 71. (p. 475) D 72. (p. 476) E 73. (p. 477) B 74. (p. 480) A 75. (p. 482) E

76. (Sec. 12.2) Difficulty: E

77. (p. 448) a. liquid

b. solid, liquid and gasc. C is the critical point. Above the critical temperature the substance cannot be liquefied, regardless of the applied pressure.d. D is in the region of the solid phase. As pressure is lowered, the line dividing the solid and gas phases will be reached. At this point the solid will sublime.Difficulty: E

78. (p. 448) Difficulty: E

79. (p. 446) 316 torr

Difficulty: M 80. (p. 446) -27.2C

Difficulty: M 81. (p. 446) 266.9 K

Difficulty: M 82. (p. 452) a. The compound must contain hydrogen bonded to an atom which is small, electronegative and has lone pairs of

electrons. The atoms which meet these criteria are N, O and F.b. High specific heat capacity; high heat of fusion; high surface tension; low density of ice compared to liquid water; other correct answers also possible.Difficulty: E

83. (p. 464) a. A unit cell is the smallest repeating unit in a crystal lattice. Shifting of the unit cell along any of three directions

must be capable of creating the entire lattice, without need to rotate the cell.b. 8.97 g/cm3

c. 128 pmDifficulty: H

84. (Sec. 12.6) 4

Difficulty: H 85. (Sec. 12.6) 287 pm

Difficulty: H 86. (Sec. 12.6) 0.524

Difficulty: M 87. (Sec. 12.6) 0.740

Difficulty: H 88. (Sec. 12.6) a. face-centered cubic; hexagonal

b. Cubic closest packing, which has the fcc unit cell, arises when close packed planes of atoms are stacked in an abcabc... arrangement; i.e., the fourth layer is above the first layer. Hexagonal close packing arises when the planes are stacked in an abab.... arrangement; i.e., the third layer is above the first.Difficulty: E

89. (p. 470) a. metallic

b. network covalentc. ionicd. atomice. molecularDifficulty: M

90. (p. 471) 2.82 10-8 cmDifficulty: H

91. (p. 475) Metals are good conductors whose conductivity decreases as the temperature rises. Semiconductors are poor

conductors, but their conductivity increases with temperature.Difficulty: M

92. (p. 475) In metals, the conduction and valence bands overlap. Electrons can freely spill into the conduction band from the

valence band, resulting in good conductivity. In semiconductors, the moderate gap between the bands results in few electrons being available to carry current, and conductivity is poor.

Difficulty: M

93. (p. 477) In pure Ge, very few electrons have sufficient energy to move into the conduction band, and conductivity is poor.

Since P has only three valence electrons to the four of Ge, there will be some vacancies in the valence band when Ge is doped with P. Movement of these holes results in current flow; it will be a p-type semiconductor.

Difficulty: M

94. (p. 480) smectic > cholesteric > nematic

Difficulty: M 95. (p. 448) FALSE 96. (p. 448) FALSE 97. (Sec. 12.2) TRUE 98. (p. 448) TRUE 99. (p. 449) FALSE 100. (p. 448) FALSE 101. (p. 446) TRUE 102. (p. 450) FALSE 103. (p. 460) FALSE 104. (p. 457) TRUE 105. (p. 456) FALSE

106. (p. 467) TRUE 107. (p. 467) FALSE 108. (p. 467) FALSE 109. (p. 475) FALSE 110. (p. 478) TRUE 111. (p. 481) FALSE 112. (p. 480) TRUE 113. (p. 483) TRUE

chemistry

Documents