Lecture 2, MWF 11:15 Day
The
multiple choice portion of this exam has 18 questions totaling 85 points.
The
written portion of this exam has 3 questions totaling 15 points.
The multiple-choice
questions are given below.
The answer key for the multiple-choice questions is given immediately following the questions.
Information for your use:
K = °C + 273 R =
0.08206 Latm/mol·K = 8.314 J/mol·K
1 atm = 760 mm Hg Normal f. pt. H2O = 0.0 °C Normal
b. pt. H2O = 100.0 °C
q = mass x specific heat x DT PV = nRT P1V1/T1=P2V2/T2
XA = nA / (nA + nB)
PA
= XAP°A DTb = Kbmi DTf = Kfmi
1.
(5
points) At room temperature and pressure, substance A is a solid, substance B
is a liquid, and substance C is a gas. According to the ideas of the kinetic
theory, at room temperature and pressure, intermolecular forces in:
(A) C are
much stronger than those in B.
(B) A are
somewhat weaker than those in B.
(C) C are
somewhat stronger than those in A.
(D) B are
very strong compared to the average kinetic energy of its molecules.
(E) C are
very weak compared to the average kinetic energy of its molecules.
2.
(5
points) In which of the following pure substances would hydrogen bonding be
expected?
(A)
all of them (C) CH2F2 (E) CH3OCH3
(B)
H2 (D) CH3CH2OH
3.
(5 points) When NaCl dissolves in water, the
solute-solvent interactions are best described as
(A)
dipole-dipole (C) ion-dipole (E) dispersion
(B)
dipole-induced
dipole (D)
ion-ion
4.
(5 points) Intermolecular attractive forces
are expected to be stronger in octane, C8H18 , than in
hexane, C6H14 , because
(A)
dipole-dipole
forces increase with molecular weight
(B)
dispersion
forces increase with molecular weight
(C)
the
larger the molecule the stronger the hydrogen bonding
(D)
the
larger the molecule the larger the dipole moment
(E)
the
larger the molecule the stronger the ion-dipole forces
5.
(4
points) Which of the following would you expect to be lower for octane, C8H18,
than for hexane, C6H14?
(A)
the
critical temperature
(B)
the
normal boiling point
(C)
the
heat of vaporization at the normal boiling point
(D)
the
vapor pressure of the liquid at 25 oC
(E)
none
of the above would be expected to be higher for hexane than for octane.
Use the following
information to answer questions 6 and 7 :
The vapor pressure of liquid
chloroform is 100 mm at 283 K and 400 mm at 316 K.
6.
(4
points) When a sample of chloroform is put in an evacuated rigid container and
maintained at 283 K, it is found that both liquid and vapor are present at
equilibrium. The pressure in the container:
(A)
is
less than 100 mm (D) is greater than 100 mm
(B)
is
equal to 100 mm (E) is unpredictable
(C)
could
be less than or equal to 100 mm
7.
(5
points) A sample of gaseous chloroform in a rigid container at a pressure of
300 mm and a temperature of 316 K is cooled at constant volume to 283 K. When
all changes have taken place, the contents of the container will be:
(A)
a
gas at a pressure of 269 mm
(B)
a
gas and a liquid at a pressure of 269 mm
(C)
a
liquid at a pressure of 269 mm
(D)
a
gas at a pressure of 100 mm
(E)
a
gas and a liquid at a pressure of 100 mm
8.
(4
points) For a given substance, which one of the following transformations would
require the most energy?
(A) solid to liquid (C) liquid to gas (E) liquid to solid
(B) solid to gas (D) gas to solid
Use the following
information for heptane (MW=100) for questions 9 and 10:
normal boiling point = 98.4 oC heat of vaporization = 34.1 kJ/mol
specific heat liquid = 2.24 J/goC
9.
(5 points) What is the vapor pressure of
heptane in mm Hg at 98.4 oC over a solution that contains 0.500 mol
of a non-volatile non-electrolyte dissolved in 200 grams of heptane?
(A) 152 (B) 323 (C) 507 (D) 608 (E) 950
10.
(6 points) How many kilojoules of energy are
required to convert a 100 gram sample of pure liquid heptane at 20.0 oC
to heptane vapor at 98.4 oC?
(A) 17.6 (B) 35.9 (C) 41.8 (D) 48.6 (E) 51.7
11.
(4 points) The solubility of sodium acetate
in water at 0°C is 119 g per 100g water. A
solution that contains 170 g sodium acetate per 100 g water at 0°C is
(A) unsaturated (C) supersaturated (E) impossible
(B) saturated (D) hyposaturated
12.
(6
points) Assuming ideal behavior, calculate the normal boiling point in °C of a solution that contains 64.5 grams of
the non-volatile non-electrolyte quinoline (MW = 129) in 500 grams of benzene.
For benzene the normal boiling point is 80.10 °C and Kb = 2.53 °C/m
(A) 77.57 (B) 80.37 (C) 82.63 (D) 84.46 (E) 98.24
13.
(4
points) Assuming ideal behavior, which of the following solutions would have
the lowest freezing point? Sucrose is a non-electrolyte.
(A) 0.20 m NaCl (C) 0.20 m CH3COOH (E) all would have the same f pt
(B) 0.20 m CaCl2 (D) 0.20 m sucrose
14.
(4
points) A 0.20 M aqueous sucrose solution is separated from a 0.10 M aqueous
sucrose solution by a semi-permeable membrane. As time passes one would expect
a net flow of _____ molecules from the _____ M solution to the other one.
(A) H2O, 0.10 (C) sucrose,
0.10 (E) both, 0.20
(B) H2O, 0.20 (D) sucrose,
0.20
Use the following data for the decomposition of NO2 at 573 K for questions 15 and 16:
NO2 (g) ® NO
(g) + 1/2 O2 (g)
Time, s |
0 |
100 |
200 |
300 |
[NO2],
M |
0.0100 |
0.0065 |
0.0048 |
0.0038 |
15.
(5
points) What is the average rate of disappearance of NO2 from t =
200 to t = 300 s in Ms-1?
(A) 1.0 x 10-5 (B) 2.4
x 10-5 (C) 1.3 x 10-5 (D) 4.3 x 10-3 (E) 4.3 x 10-5
16.
(4
points) What is the average rate of appearance of O2 over the same
time period ?
(A) 5.0 x 10-6 (B) 1.0
x 10-5 (C) 2.0 x 10-5 (D) 5.0 x 10-5 (E) 8.6 x 10-3
17.
(5
points) The rate law for the NO2 decomposition reaction is given by
Rate = k[NO2]2
. If the rate constant is 0.54 M-1s-1, what is the rate
of the reaction in Ms-1 when [NO2] = 0.020 M ?
(A) 1.1 x 10-2 (B) 2.2 x 10-2 (C)
5.8 x 10-3 (D) 2.2 x 10-4 (E)
6.9 x 10-2
18.
(5 points) The reaction 2Cl-(aq) + 2H+ (aq) +
H2O2 (aq) ® Cl2(aq) + 2H2O(l) is third order overall and first order in each reactant. The rate
law for the reaction is:
(A) Rate = k[Cl-]2[H+]2[H2O2] (D) Rate = k[Cl-]3/2[H+]3/2[H2O2]3
(B) Rate = k[Cl-]3[H+]3[H2O2]3 (E)
Rate = k[Cl-]3[H+]3[H2O2]3/2
(C) Rate = k[Cl-][H+][H2O2]
The following list gives the number of points for each answer, in the order ABCDE, for each question. The correct answer to each question is the one worth the most points.
1
00005
2
00050
3
00500
4
05000
5
00040
6
04000
7
00005
8
04000
9
30050
10
30006
11
00400
12
30600
13
04000
14
40000
15
50000
16
40200
17
00050
18
00500