66) Some things take longer to cook at high altitudes than at low altitudes because __________.
A) water boils at a lower temperature at high altitude than at low altitude
B) water boils at a higher temperature at high altitude than at low altitude
C) heat isn’t conducted as well in low density air
D) natural gas flames don’t burn as hot at high altitudes
E) there is a higher moisture content in the air at high altitude
67) The vapor pressure of a liquid __________.
A) increases linearly with increasing temperature
B) increases nonlinearly with increasing temperature
C) decreases linearly with increasing temperature
D) decreases nonlinearly with increasing temperature
E) is totally unrelated to its molecular structure
68) The slope of a plot of the natural log of the vapor pressure of a substance versus 1/T is __________.
A) ΔHvap
B) –ΔHvap
C)
vap
1
H
D)
vap
H
R
−
E)
vap
1
H
−
69) On a phase diagram, the critical pressure is __________.
A) the pressure required to melt a solid
B) the pressure below which a substance is a solid at all temperatures
C) the pressure above which a substance is a liquid at all temperatures
D) the pressure at which a liquid changes to a gas
E) the pressure required to liquefy a gas at its critical temperature
70) On a phase diagram, the critical temperature is __________.
A) the temperature below which a gas cannot be liquefied
B) the temperature above which a gas cannot be liquefied
C) the temperature at which all three states are in equilibrium
D) the temperature required to melt a solid
E) the temperature required to cause sublimation of a solid
71) On a phase diagram, the melting point is the same as __________.
A) the triple point
B) the critical point
C) the freezing point
D) the boiling point
E) the vapor-pressure curve
72) When the phase diagram for a substance has a solid-liquid phase boundary line that has a negative
slope (leans to the left), the substance __________.
A) can go from solid to liquid, within a small temperature range, via the application of pressure
B) sublimes rather than melts under ordinary conditions
C) cannot go from solid to liquid by application of pressure at any temperature
D) cannot be liquefied above its triple point
E) melts rather than sublimes under ordinary conditions
73) The predominant intermolecular force in CaBr2 is __________.
A) London-dispersion forces
B) ion-dipole forces
C) ionic bonding
D) dipole-dipole forces
E) hydrogen bonding
74) Which of the following is most likely to exhibit liquid-crystalline behavior?
A) CH3CH2-C(CH3)2-CH2CH3
B) CH3CH2CH2CH2CH2CH2CH2CH3
C) CH3CH2CH2CH2CH2–Na+
D)
E)
75) Which of the following characteristics would prevent liquid crystal behavior?
A) long axial structure
B) ionic configuration
C) carbon-carbon single bonds
D) double bonding
E) polar groups
76) In the smectic A liquid-crystalline phase, __________.
A) the molecules are aligned along their long axes, with no ordering with respect to the ends of the
molecules
B) the molecules are arranged in sheets, with their long axes parallel and their ends aligned as well
C) the molecules are aligned with their long axes tilted with respect to a line perpendicular to the plane
in which the molecules are stacked
D) disk-shaped molecules are aligned through a stacking of the disks in layers
E) the molecules are oriented in a totally random fashion
77) In the __________ liquid crystalline phase, the component molecules exhibit only one dimensional
ordering.
A) nematic
B) smectic A
C) smectic B
D) smectic C
E) cholesteric
78) In the ________ liquid crystalline phase, the component molecules are aligned along their long axis
and are arranged in layers with the molecules in each plane twisted slightly in relation to the molecules
in the planes above and below.
A) nematic
B) smectic A
C) smectic B
D) smectic C
E) cholesteric
79) Cholesteric liquid crystals are colored because __________.
A) each molecule is a chromophore
B) of the slight twist between layers
C) of the large spacing between layers
D) of the large number of conjugated bonds
E) all of the molecules contain multiple benzene rings
80) Molecules with only single bonds do not generally exhibit liquid-crystalline properties because
__________.
A) molecules without multiple bonds lack the rigidity necessary for alignment
B) molecules without multiple bonds are too small to exhibit liquid-crystalline properties
C) molecules with only single bonds are gases
D) molecules with only single bonds are too big to exhibit liquid-crystalline properties
E) molecules without multiple bonds lack the flexibility necessary for alignment
81) For a given substance that exhibits liquid-crystalline properties, the transition from solid to liquid-
crystal state occurs __________.
A) over a range of temperatures between the melting point of the solid and the boiling point of the liquid
B) at the melting point of the solid
C) over a range of temperatures that includes the melting point of the solid
D) at a well defined temperature above the melting point of the solid
E) at a well defined temperature below the melting point of the solid
82) For a given substance that exhibits liquid-crystalline properties, the liquid-crystalline state exists
__________.
A) at one particular temperature below the melting point of the solid
B) in a range of temperatures below the melting point of the solid
C) at one particular temperature above the melting point of the solid
D) in a range of temperatures above the melting point of the solid
E) in a range of temperatures from below the melting point to above the melting point
11.2 Bimodal Questions
1) Based on molecular mass and dipole moment of the five compounds in the table below, which should
have the highest boiling point?
A) CH3CH2CH3
B) CH3OCH3
C) CH3Cl
D) CH3CHO
E) CH3CN
2) The heating curve shown was generated by measuring the heat flow and temperature for a solid as it
was heated. The slope of the __________ segment corresponds to the heat capacity of the liquid of the
substance.
A) AB
B) BC
C) CD
D) DE
E) EF
3) The heating curve shown was generated by measuring the heat flow and temperature for a solid as it
was heated. The slope of the __________ segment corresponds to the heat capacity of the solid.
A) AB
B) BC
C) CD
D) DE
E) EF
4) The heating curve shown was generated by measuring the heat flow and temperature for a solid as it
was heated. The slope of the __________ segment corresponds to the heat capacity of the gas.
A) AB
B) BC
C) CD
D) DE
E) EF
5) The heating curve shown was generated by measuring the heat flow and temperature of a solid as it
was heated. The heat flow into the sample in the segment __________ will yield the value of the ΔHvap
of this substance.
A) AB
B) BC
C) CD
D) DE
E) EF
6) The heating curve shown was generated by measuring the heat flow and temperature of a solid as it
was heated. The heat flow into the sample in the segment __________ will yield the value of the
ΔHfusion of this substance.
A) AB
B) BC
C) CD
D) DE
E) EF
7) On the phase diagram shown above, segment __________ corresponds to the conditions of
temperature and pressure under which the solid and the gas of the substance are in equilibrium.
A) AB
B) AC
C) AD
D) CD
E) BC
8) On the phase diagram shown above, the coordinates of point __________ correspond to the critical
temperature and pressure.
A) A
B) B
C) C
D) D
E) E
9) On the phase diagram shown above, the coordinates of point __________ correspond to the triple
point.
A) A
B) B
C) C
D) D
E) E
10) The phase diagram of a substance is given above. The region that corresponds to the solid phase is
__________.
A) w
B) x
C) y
D) z
E) x and y
11) The normal boiling point of the substance with the phase diagram shown above is __________°C.
A) 10
B) 20
C) 30
D) 40
E) 50
12) The normal melting point of the substance with the phase diagram shown above is __________°C.
A) 15
B) 25
C) 35
D) 45
E) 55
13) The phase diagram of a substance is shown above. The area labeled __________ indicates the gas
phase for the substance.
A) w
B) x
C) y
D) z
E) y and z
14) The phase diagram of a substance is shown above. The area labeled __________ indicates the solid
phase for the substance.
A) w
B) x
C) y
D) z
E) y and z
15) The phase diagram of a substance is shown above. The area labeled __________ indicates the liquid
phase for the substance.
A) w
B) x
C) y
D) z
E) y and z
16) According to the phase diagram shown above, the normal boiling point of this substance is
__________°C.
A) -3
B) 10
C) 29
D) 38
E) 0
17) According to the phase diagram shown above, the normal melting point of this substance is
__________°C.
A) -13
B) 10
C) 29
D) 38
E) 0
18) A __________ liquid crystal has the least order and is the most liquid-like.
A) nematic
B) smectic
C) cholesteric
D) smectic B
E) smectic C
19) Which type of liquid crystal is colored and changes color with temperature?
A) nematic
B) smectic A
C) cholesteric
D) smectic B
E) smectic C
11.3 Algorithmic Questions
1) The enthalpy change for converting 1.00 mol of ice at -50.0°C to water at 70.0°C is __________ kJ.
The specific heats of ice, water, and steam are 2.09 J/g-K, 4.18 J/g-K, and 1.84 J/g-K, respectively. For
H2O, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.67 kJ/mol
A) 12.28
B) 6.41
C) 13.16
D) 7154
E) 9.40
2) The enthalpy change for converting 10.0 g of ice at -25.0°C to water at 80.0°C is __________ kJ. The
specific heats of ice, water, and steam are 2.09 J/g-K, 4.18 J/g-K, and 1.84 J/g-K, respectively.
For H2O, ΔHfus = 6.01 kJ/mol, and ΔHvap = 40.67 kJ/mol
A) 12.28
B) 6.16
C) 3870
D) 7.21
E) 9.88
3) The heat of fusion of water is 6.01 kJ/mol. The heat capacity of liquid water is 75.3 J/mol ∙ K. The
conversion of 50.0 g of ice at 0.00°C to liquid water at 10.0°C requires __________ kJ of heat.
A) 2110
B) 18.8
C) 2.11
D) 16.7
E) Insufficient data are given.
4) Calculate the enthalpy change (in kJ) associated with the conversion of 25.0 grams of ice at -4.00°C
to water vapor at 106.0°C. The specific heats of ice, water, and steam are 2.09 J/g-K, 4.18 J/g-K, and
1.84 J/g-K, respectively. For H2O, ΔHfus = 6.01 kJ/mol and ΔHvap = 40.67 kJ/mol.
A) 64.8
B) 75.8
C) 11000
D) 12000
E) 112
5) Ethanol (C2H5OH) melts at -114°C. The enthalpy of fusion is 5.02 kJ/mol. The specific heats of solid
and liquid ethanol are 0.97 J/g-K and 2.3 J/g-K, respectively. How much heat (kJ) is needed to convert
25.0 g of solid ethanol at -135°C to liquid ethanol at -50°C?
A) 207.3
B) -12.7
C) 6.91
D) 4192
E) 9.21
6) Based on the figure above, the boiling point of diethyl ether under an external pressure of 1.32 atm is
__________°C.
A) 10
B) 20
C) 30
D) 40
E) 0
7) Based on the figure above, the boiling point of ethyl alcohol under an external pressure of 0.0724 atm
is __________°C.
A) 80
B) 60
C) 70
D) 40
E) 20
8) Based on the figure above, the boiling point of water under an external pressure of 0.493 atm is
__________°C.
A) 80
B) 40
C) 60
D) 70
E) 90
9) The phase diagram of a substance is given above. This substance is a __________ at -10°C and 1.0
atm.
A) liquid
B) solid
C) gas
D) supercritical fluid
E) crystal
11.4 Short Answer Questions
1) In general, intramolecular forces determine the __________ properties of a substance and
intermolecular forces determine its __________ properties.
2) London Dispersion Forces tend to __________ in strength with increasing molecular weight.
3) The direct conversion of a solid to a gas is called __________.
4) The initial discovery of a liquid crystal resulted from studies on what compound?
11.5 True/False Questions
1) The principal source of the difference in the normal boiling points of ICl (97°C; molecular mass 162
amu) and Br2 (59°C; molecular mass 160 amu) is both dipole-dipole interactions and London dispersion
forces.
2) The boiling points of normal hydrocarbons are higher than those of branched hydrocarbons of similar
molecular weight because the London-dispersion forces between normal hydrocarbons are greater than
those between branched hydrocarbons.
3) Heats of vaporization are greater than heats of fusion.
4) Under ordinary conditions, a substance will sublime rather than melt if its triple point occurs at a
pressure above atmospheric pressure.
5) Molecules containing only single bonds do not exhibit liquid-crystal behavior because free rotation
can occur around single bonds making these molecules flexible.