1. No category

1. (6 pts) A sample of gas with a volume of 750 mL exerts a pressure of 756
mm Hg at 30.00C. What pressure (atm) will the sample exert when it is
compressed to 250 mL and cooled to -25.00C?
a)
b)
c)
d)
e)
1.3 x 103 atm
2.44 atm
8.35 atm
4.21 x 10-3 atm
86.5 atm
2. (6 pts) Consider a cylinder fitted with a moveable piston that can expand
against the atmosphere. The initial pressure, volume and absolute
temperature inside the cylinder are P1, V1 and T1. What is the new
temperature of the system when the pressure is increased to three times
the original pressure and the volume is decreased to one half of the
original volume?
a)
b)
c)
d)
e)
2.25 T1
3 T1
1/5 T1
1.5 T1
6 T1
3. (7 pts) A badly tuned automotive engine can release 50 moles of carbon
dioxide per hour. At 350C, what volume of carbon dioxide in a six-hour
period (driving from Columbus to Chicago) is released if the atmospheric
pressure is 748 mm Hg?
a)
b)
c)
d)
e)
2.5 x 105 L
7.7 x 103 L
1.3 x 103 L
10 L
5.3 x 105 L
1
4. (5 pts) Which of the following statements about ideal gases is true?
a) Equal volumes of gases at the same temperature and pressure contain
different numbers of molecules.
b) The volume of a fixed quantity of gas maintained at constant pressure is
inversely proportional to temperature.
c) The average kinetic energy of gas molecules is greater than the energy of
attraction of gas molecules.
d) Standard temperature and pressure are 25.0oC and 1.0 atm
e) In a given sample of an ideal gas, gas molecule behavior is dependent
upon molecular attraction and repulsion.
5. (7 pts) The safety air bags in automobiles are inflated by nitrogen gas
generated by the rapid decomposition of sodium azide, NaN3.
2 NaN3(s) → 2 Na(s) + 3 N2(g)
If an air bag has a volume of 48 L and is to be filled with nitrogen gas at a
pressure of 1.15 atm at a temperature of 27.00C, how many grams of NaN3 must
be decomposed?
(MW NaN3 = 65.00, Na = 23.00, N2 = 28.00)
a)
b)
c)
d)
e)
97 g
48 g
25 g
73 g
12 g
6. (6 pts) A 1.00 g sample of SFx has a volume of 270 mL at 745 mm Hg and
750C. What is the value of x? (Atomic weights: S = 32.06, F = 19.00)
a) 1
b) 2
c) 3
d) 4
e) 6
2
7. (6 pts) A mixture of 40.0 g helium and 40.0 g argon occupies 3.75 L at 75.00C.
What is the partial pressure (atm) of argon?
(AW: He = 4.00, Ar = 40.00)
a) 7.61 atm
b) 9.42 atm
c) 27.4 atm
d) 81.8 atm
e) none of the above
8. (5 pts) Which of the following is not a postulate of the kinetic molecular theory
of gases?
a) Gases consist of discrete particles that are in constant chaotic motion.
b) The molecules possess a volume that is negligibly small compared to the
volume of the container.
c) The average kinetic energy of the molecules is directly proportional to the
absolute temperature.
d) The pressure and volume are inversely related.
e) All of the above are postulates of the kinetic molecular theory of gases.
9. (6 pts) The van der Waal’s constants for three gases are listed below:
a ( L2 atm/mol)
A
B
C
12.56
1.345
6.714
b (L/mol)
0.08710
0.03219
0.05636
From your knowledge of the physical significance of a and b, intermolecular
forces and the sizes of atoms and molecules, identify the gases. The
possibilities are SO2, Ar and CH3CH2OH. Which of the following statements are
correct?
a) There is insufficient information to identify the gases.
b) A is CH3CH2OH and B is Ar.
c) A is Ar and B is CH3CH2OH.
d) A is SO2 and B is CH3CH2OH.
e) A is CH3CH2OH and B is SO2.
3
10. (7 pts) A gas of unknown molecular mass was allowed to effuse through a
small opening under constant pressure conditions. It required 62 s for 1.0 L of
the unknown gas to effuse. Under identical conditions, it required 31 s for 1.0 L
of oxygen gas to effuse. Calculate the molar mass (g/mol) of the unknown gas.
a) 45 g/mol
b) 256 g/mol
c) 175 g/mol
d) 325 g/mol
e) 128 g/mol
11. (6 pts) Select the member of each pair with stronger intermolecular forces.
CH4
a)
b)
c)
d)
e)
CCl4
CH4
CCl4
CCl4
CH4
CH4
CH3COCH3 CH3CH2CH3
CH3CH2CH3
CH3COCH3
CH3COCH3
CH3COCH3
CH3COCH3
H2O H2S
H2O
H2O
H2S
H2S
H2O
12. (6 pts) Which of the following is true?
I. Two of the following molecules can form hydrogen bonds: CH3F,
CH3NH2, CH3OH, CH3Br.
II. HBr has a higher boiling point than HI.
III. Ethyl alcohol (CH3CH2OH) has a lower boiling point than ethylene glycol
(HOCH2CH2OH).
IV. Propyl alcohol (CH3CH2CH2OH) has a higher boiling point that isopropyl
alcohol (CH3)2CHOH
a) I, II, IV
b) I, II, III
c) II, III, IV
d) I, III, IV
e) III, IV
13. (5 pts) If a substance has weak molecular forces, it has a ______ boiling
point, a _______heat of vaporization and a __________vapor pressure.
a)
b)
c)
d)
e)
low
high
low
high
high
large
large
small
small
large
low
high
high
low
low
4
14. (7 pts) Calculate the heat (kJ) evolved when 50.0 g of steam at 120.0oC are
converted to ice at -30.0oC.
Specific heat ice
Specific heat water
Specific heat steam
2.09 J/goC
4.18 J/goC
1.84 J/goC
ΔHfus(ice)
334 J/g
ΔHvap(liquid water) 2260 J/g
a) -1.92 x 105 kJ
b) -1.55 x 102 kJ
c) -1.32 x 102 kJ
d) -4.87 x 102 kJ
e) none of the above
15. (7 pts) The vapor pressure of water at 370C is 47.1 torr and its enthalpy of
vaporization is 44.0 kJ/mol. Calculate the vapor pressure of water at 870C.
a)
b)
c)
d)
e)
112 torr
256 torr
713 torr
52 torr
505 torr
16. (5 pts) Rutile is a mineral composed of titanium and oxygen. In the unit cell,
there are titanium atoms at each corner and a titanium atom at the center. Four
oxygen atoms are on the opposite faces of the cell, two are entirely within the
cell. What is the chemical formula of this mineral?
a) TiO2
b) Ti2O
c) TiO
d) Ti3O2
e) Ti3O4
5
For question 17, sketch the phase diagram:
(A) triple point = 200C, 0.03 atm
(B) critical point = 1500C, 30 atm
(C) normal melting point = -200C
(D) normal boiling point = 800C
(E) Sublimation at -400C requires
0.008 atm
30
1.0
Pressure
(atm)
0.03
(not to scale)
0.008
-50
0
50
100
0
150
Temperature ( C)
(7 pts) Which of the following statements is correct?
a) The melting point of the solid increases as pressure is increased.
b) Line AC represents sublimation.
c) As the pressure is increased from 0.0002 atm to 40 atm at 600C, two phase
changes occur.
d) The solid is denser than the liquid.
e) As the temperature is increased from -400C to 1250C at 0.9 atm, two phase
changes occur.
18. (7 pts) An element crystallizes in a face centered cubic lattice and the edge
length of the unit cell is 5.59 x 10-8 cm. The density is 3.19 g/cm3. What is the
element?
a) He
b) Ne
c) Ar
d) Kr
e) Xe
19. (5 pts) Which of the following statements are false?
I. The hexagonal close packed structure is ABABAB, each particle has
12 nearest neighbors and there is 48% open space.
II. For a face centered structure, the relationship between edge length (l)
and the radius of a particle is l = 4r/√2.
III. Ionic solids conduct electricity.
IV. Molecular solids generally have lower melting points than covalent
network solids.
V. There is one atom per unit cell for a simple cubic unit cell.
a) I, III
b) III, V
c) II, IV
d) I, V
e) II, V
6
20. (5 pt) Choose the member of each pair that is expected to have the higher
normal melting point.
NaCl or C
a) NaCl
b) NaCl
c) C
d) NaCl
e) C
CO2
SiO2
CO2
SiO2
SiO2
CO2 or SiO2
O2
Na
Na
O2
Na
O2 or Na
Li or H2O
H2O
Li
Li
H2O
Li
21. (5 pts) The lattice energy of aluminum trifuloride is 5220 kJ/mol. The heat of
solution is -27 kJ/mol at 250C. Determine the heat of hydration (kJ/mol).
a)
b)
c)
d)
e)
5247 kJ/mol
5193 kJ/mol
0 kJ/mol
-5193 kJ/mol
-5247 kJ/mol
22. (6 pts) Which of the following statements about these compounds is false?
a) A solution containing 35 g of
B in 85 g H2O at 80oC is
unsaturated.
b) The heat of solution of B is
endothermic.
c) If a saturated solution of A
is heated from 10oC to
90oC, the solution
remains saturated.
d) 20 g of C can be completely
dissolved in 100 g of H2O at
20oC.
e) None of the above
statements are false.
7
23. (5 pts) Which of the following of each pair is expected to be more soluble in
water?
CH3OH or CH3Br SiO2 or H2CO3 C6H12 or C6H12O6
a) CH3OH
b) CH3OH
c) CH3Br
d) CH3Br
e) CH3OH
SiO2
H2CO3
SiO2
SiO2
H2CO3
C6H12O6
C6H12O6
C6H12
C6H12O6
C6H12
24. (6 pts) What is the molality of a 1.06 M aqueous solution of sugar (C6H12O6,
342.3 g/mol) which has a density of 1.14 g/mL?
a) 1.36 molal
b) 1.06 molal
c) 0.927 molal
d) 0.634 molal
e) 0.442 molal
25. (7 pts) Calculate the mole fraction of ethanol in the vapor phase at 63.50C for
an ideal solution containing 96.0 gm of pure methanol (CH3OH, 32.0 g/mol) and
92.2 gm of pure ethanol (CH3CH2OH, 46.1 g/mol). The vapor pressure of
methanol and ethanol at 63.50C is 717.2 mm and 400.0 mm mercury,
respectively.
a) 0.943
b) 0.701
c) 0.466
d) 0.271
e) none of the above
8
26. (5 pts) What is the boiling point change for a solution containing 0.328 moles
of naphthalene (a nonvolatile, nonionizing compound) in 250. g of liquid benzene
(Kb = 2.53 0C/m, BP = 80.10C)
a)
b)
c)
d)
e)
3.320C
7.410C
1.930C
4.310C
10.70C
27. (6 pts) When a 20.0 g sample of an unknown compound is dissolved in 500.0
g of benzene, the freezing point of the resulting solution is 3.770C. The freezing
point of pure benzene is 5.480C and the Kf for benzene is 5.120C/m. Calculate
the molar mass of the unknown compound.
a)
b)
c)
d)
e)
160. g/mol
80.0 g/mol
100. g/mol
140 g/mol
120 g/mol
28. (5 pts) The molar mass of a solid as determined by freezing point depression
is 10% higher than the true molar mass. Which of the following experimental
errors could not account for this discrepancy?
a)
b)
c)
d)
e)
Not all the solid was dissolved.
More than the recorded amount of solvent was pipetted into the solution.
The solid dissociated slightly into two particles when it dissolved.
Some solid was left of the weighing paper.
Before the solution was prepared, the container was rinsed with solvent
and not dried.
9
29. (7 pts) Cox-1 is a protein that acts as an enzyme to speed up the production
of prostaglandins. A solution contains 2.88 g of Cox-1 in 125 mL of water. This
solution has an osmotic pressure of 24.8 mm Hg at 270C. What is the molecular
weight of this sample of Cox-1?
a)
b)
c)
d)
e)
4.81 X 103 g/mol
3.20 x 104 g/mol
8.05 x 105 g/mol
5.75 x 103 g/mol
1.74 x 104 g/mol
30. (6 pts) Which of the following solutions should have the highest freezing
point?
a)
b)
c)
d)
e)
0.01 m KBr
0.005 m (NH4)3PO4
0.008 m MgCl2
0.01 m glucose
0.006 Ca(OH)2
10
Helpful Information
R = 0.08206 L-atm/mol-K = 8.3145 J/mol-K
Avogadro’s number = 6.02 x 1023 particles/mol
1 Angstrom = 1 x 10-10 m = 1 x 10-8 cm
T(K) = T(0C) = 273.15 K
Molar volume at STP = 22.4 L
PV = nRT
KE = ½ mv2
Pi = ΧiPtotal
density of Hg = 13.55 g/cm3 at 200C
[ P + n2a/V2 ] [ V – nb ] = nRT
KEavg = ½ mµ2
µ = ( 3RT/MW )1/2
ln(P2/P1) = ΔHvap/R(1/T1-1/T2)
11