Chemistry 106: General Chemistry
Syracuse University Project Advance
Exam #4, Fall 2005
Name
Date
The last page of each examination is a periodic table.
R=0.08206 L-atm / mole-K
1. Identify the phase transition occurring in each of the following
1. The water level in an aquarium tank falls continuously (the tank has no leaks).
2. Chlorine gas is passed into a very cold test tube where it turns into a yellow
liquid.
3. Molten lava from a volcano cools and turns to solid rock.
a)
b)
c)
d)
e)
1-vaporization
1-vaporization
1-condensation
1-freezing
1-condensation
2-condensation
2-freezing
2-vaporization
2-condensation
2-freezing
3-freezing
3-condensation
3-freezing
3-vaporization
3-vaporization
2. Which of the following has the lowest melting point?
a)
b)
c)
d)
e)
KCl
MgO
RbCl
CsCl
NaCl
3. Which one of the following do you expect to be more volatile?
a)
b)
c)
d)
e)
CBr2H2
CBr4
CBr3H
CCl4
CCl3H
4. In which of the following locations would the boiling point of water be highest?
a)
b)
c)
d)
e)
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New Mexico where the average pressure is 710 torr.
Mt. Everest where the average pressure is 244 torr.
Denver, Colorado where the average pressure is 650 torr.
New York City where the average pressure is 760 torr.
A pressure cooker where the average pressure is 1400 torr.
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Fall 2005 Exam #4
5. The critical temperature for HCl is 52°C. At temperatures above 52°C,
a)
b)
c)
d)
e)
HCl decomposes into atoms of the elements, H and Cl.
HCl decomposes into molecules of the elements, H2 and Cl2.
HCl cannot be liquified by applying even a very large pressure.
the H-Cl electron bond pair is completely transferred to the chlorine.
the H-Cl electron bond pair is completely transferred to the hydrogen.
6. The principal difference in respective normal boiling points of ICl (97°C; molecular
mass 162 amu) and Br2 (59°C; molecular mass 160 amu) is due to
a)
b)
c)
d)
e)
London-dispersion forces
dipole-dipole interactions
hydrogen bonding
both hydrogen-bonding and dipole-dipole interactions
both dipole-dipole interactions and London dispersion forces.
7. The intermolecular force(s) responsible for the substance OH2 having the highest
boiling point in the series: OH2, SH2, SeH2, TeH2 is/are
a)
b)
c)
d)
e)
dipole-dipole interactions.
London dispersion forces.
mainly hydrogen bonding but also dipole-dipole interactions.
mainly London dispersion forces but also dipole-dipole interactions.
hydrogen bonding.
8. The total pressure of a gas mixture of helium, neon, and argon is 8.40 atm. What is
the mole fraction of argon if the respective partial pressures of helium and neon are
1.50 and 2.00 atm?
a)
b)
c)
d)
e)
0.179
0.238
0.357
0.583
0.417
9. The shape of a liquid’s meniscus is determined by
a) the viscosity of the liquid
b) the type of material the container is made of
c) the relative magnitudes of cohesive forces in the liquid and adhesive forces
between the liquid and the container
d) the amount of hydrogen bonding in the liquid
e) the volume of the liquid
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Fall 2005 Exam #4
10. Viscosity is
a) the “skin” on a liquid surface caused by intermolecular attraction
b) the resistance to flow
c) the same as density
d) inversely proportional to molar mass
e) unaffected by temperature
11. The heat of fusion of water is 6.01 kJ / mole. The heat capacity of liquid water is
75.2 J / mole * K. The conversion of 50 grams of ice at 0oC to liquid at 220C requires
how many kJ of heat?
a) 3.8 x 102
b) 21.3
c) 17.2
d) 0.469
e) insufficient data are given
12. The vapor pressure of any substance at its normal boiling point is
a) 1 Pa
b) 1 torr
c) 1 atm
d) equal to atmospheric pressure
e) equal to the vapor pressure of water
13. The molality of a benzene solution in carbon tetrachloride formed by mixing 12
grams of C6H6 with 38 grams of CCl4 is
a) 4.04
b) 0.240
c) 0.622
d) 0.316
e) 0.508
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14. What kind of attractive forces dominate the following systems:
NaCl (s)
a) ion-ion forces
Xe (l)
ion-dipole forces
b) ion-ion forces
London Dispersion
forces
ion-ion forces
c) London
Dispersion forces
d) ion-ion
ion-dipole
KBr (aq)
London Dispersion
Forces
ion-dipole forces
H2O (s)
ion-ion forces
ion-dipole forces
ion-dipole forces
London Dispersion
forces
Hydrogen bonds
Hydrogen bonds
15. A saturated magnesium chloride solution is 34.6% MgCl2(aq) and has a density of
1.27 g/mL. What is the molality (m) of the solution? The molar mass of MgCl2 is
95.21 g/mol and that of water 18.016 g/mol.
a)
b)
c)
d)
e)
5.56
0.0363
7.06
4.62
none of these.
16. We wish to lower the freezing point of the water in an automobile radiator to -40°F.
The total mass of water present is 12.0 kg. For which one of the following
compounds would we have to use the greatest mass of solute to achieve this?
(Kf for water = -1.86°C/m).
a)
b)
c)
d)
e)
Formula
Molar Mass (g/mol)
C2H5OH
CH3H6(OH)2
CaCl2
NaCl
AIF3
46
76
111
58.5
84
Van’t hoff i factor
(# ions)
1
1
3
2
4
17. The process of solute particles being surrounded by solvent particles is known as
a) salutation
b) agglomeration
c) salvation
d) agglutination
e) dehydration
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18. The phrase “like dissolves like” refers to the fact that
a) gases can only dissolve other gases
b) polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar
solutes
c) solvents can only dissolve solutes of similar molar mass
d) condensed phases can only dissolve other condensed phases
e) polar solvents dissolve nonpolar solutes and vice versa
19. A saturated solution
a) contains as much solvent as it can hold
b) contains no double bonds
c) contains dissolved solute in equilibrium with undissolved solid
d) will rapidly precipitate if a seed crystal is added
e) can not be attained
20. A 0.1 m solution of which of the following solutes will have the lowest vapor
pressure?
a) KClO4
b) Ca(ClO4)2
c) Al(ClO4)3
d) sucrose
e) NaCl
21. The freezing point of ethanol (C2H5OH, mw = 46 g/mole) is -114.6oC. The molal
freezing point depression constant for ethanol is 2 oC / m. What is the freezing point
in oC of a solution prepared by dissolving 50 grams of glycerine (C3H8O3 ,
mw = 92 g / mole), a nonelectrolyte, in 200 grams of ethanol?
a) -115
b) -5.4
c) -132
d) -120
e) -240
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22. Which liquid will have the highest freezing point?
a) 0.5 m KF (aq)
b) 0.75 m glucose (aq)
c) 0.75 m sucrose (aq)
d) 0.24 m FeI3 (aq)
e) pure water
23. Polyethylene is a synthetic polymer or plastic with many uses. If 1.4 grams of a
polyethylene sample was dissolved in enough benzene to make 100 ml of solution
and the osmotic pressure was found to be 1.86 torr at 25oC, what is the molecular
weight of the polyethylene in g / mole?
a) 1.06 x 108
b) 11,900
c) 5720
d) 3.39 x 106
e) 140,000
24. Two teaspoons of sugar, C12H22O11, in a cup of tea correspond to 10 grams of sugar in
200 grams of water. What is the mole fraction of sugar in this solution?
a) 0.05
b) 0.0026
c) 0.146
d) 0.048
e) 1.15 x 10-4
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You MUST show all work for the following extra credit questions.
EC 1. The term “proof” is defined as twice the percent by volume of pure ethanol (ethyl
alcohol) in solution. Thus, a solution that is 95% (by volume) ethanol is 190 proof.
What is the molarity of ethanol in a 92 proof ethanol/water solution. The density of
ethanol is 0.80 g / ml, the density of water is 1.0 g / ml and the molecular weight of
ethanol is 46 g / mole.
EC 2. At 30oC the vapor pressure of pure benzene is 126 torr, while that of pure toluene
is 40 torr. A solution is prepared by combining 0.3 mole of benzene with 0.5 mole of
toluene. The vapor pressure of this solution in torr is
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