Summer 2012
Page 1
CHEMISTRY 104
Hour Exam I I
M U L T I P L E C H O I C E - Three (3) points each.
Histidine, one of the 20 naturally occurring amino acids, has the following skeletal structure.
Complete a Lewis structure for histidine and answer the following two questions.
\
H
1.
H
H
C
1
O
N
C
H
2
C
H
H
O
H
b. 1
c. 2
d. 3
e. 4
There are
The bond
The bond
There are
A l l of the
four carbon atoms in histidine that are sp^ hybridized.
angle about the oxygen atom labeled 1 is approximately 109''.
angles about the carbon atom labeled 2 is approximately 120°.
7 lone pairs of electrons in the complete Lewis structure.
nitrogen atoms are sp*^ hybridized.
A student incorrectly named a compound 4-ethyl-2,3-diisopropylpentane. What is the
correct lUPAC name for this compound?
a.
b.
c.
d.
e.
4.
N
Which of the following statements is false concerning the structure of histidine?
a.
b.
c.
d.
e.
3.
C
How many n bonds are in histidine?
a. 0
2.
H
2,3-diisopropyl-4-methylhexane
4,5-diisopropyl-3-methylhexane
4-isopropyl-3,5,6-trimethylheptane
4-isopropyl-2,3,5-trimethylheptane
2,3,5-trimethyl-4-sec-butylhexane
When CsHg is combusted in a propane torch, how many moles of 02(g) are necessary
for the complete combustion of one mole of CsHg?
a. 2
b. 4
c. 5
d. 6
e. 7
Summer 2012
Page 2
CHEMISTRY 104
Hour Exam I I
5.
Which of the following compounds has at least one carbon atom with sp hybridization?
a.
b.
c.
d.
e.
6.
1 -chloro-4-methyl-2-heptyne
cyclopropane
3 -methyl-1 -cyclopentene
2-hexene
3,4-dibromo-2,3,4,5-tetramethylhexane
Which of the following compounds has free rotation about every bond in the molecule?
a. 1 -chloro-4-methyl-2-heptyne
b. cyclopropane
c. 3-methyl-1 -cyclopentene
d. 2-hexene
e. 3,4-dibromo-2,3,4,5-tetramethylhexane
7.
When C4H8 is treated with water and H"^, a tertiary alcohol is the major product.
Which of the following structures could represent C4H8 in this reaction?
a.
c.
CH3CH=CHCH3
-CH3
H3C
b.
CH3CH2CH=CH2
d.
H2C
CH2
H2C
CH2
CH2
e. none of these
8.
Consider the four possible monochlorination products (C5H9CI) formed from the
following reaction. How many of the monochlorination products can exhibit cis/trans
isomerism?
CH,
^H
a. 0
b. 1
c. 2
+ CI2 ^^^^^^ C5H9CI + HCl
d. 3
e. 4 (all)
CHEMISTRY 104
Hour Exam I I
9.
Summer 2012
Page 3
Which of the following statements is false concerning benzene, C6H6?
a. Benzene rings are a predominate structural feature of aromatic compounds,
b. Benzene exhibits 109° bond angles.
c. Benzene is, in general, less reactive than alkenes due to the delocalized n electrons in
benzene.
d. Benzene cannot exhibit cis/trans isomerism.
e. Benzene has two equivalent (resonance) Lewis structures.
10.
Which of the following are the same molecule (are conformations of each other)?
CH3
I.
CH3
CH2CHCH2CHCH3
CH.
II.
CH3CHCH2CH2CHCH3
CH,
III.
CH3CHCHCH2CH2
CH,
CH,
CH,
CH,
CH3
IV. CH3CHCH2
CH3
V. CH3CH
CH2CHCH3
CH3CH2CHCH3
CH2CH3
11.
a. I and I I I
b. I I and I I I
d.
e. I , I I , and IV
I , IV, and V
c. I , I I I and V
Which of the following compounds can exhibit cis-trans isomerism?
I.
CH2=CH
CH2CH2CH3
III. C H 3 C H 2 — C H = C H
CH2CH3
II.
CH3CH2—C=C
IV. C H 3 C H 2 — C H = C
3^n2CH,
a. I , I I , I I I , and I V
b.
d. I l l only
e. I and IV
I l l and IV
c. I , I I I , and IV
CH3
CH2CH3
CHEMISTRY 104
Hour Exam II
12.
Which of the following compounds contain two and only two chiral carbon atoms?
e.
13.
Summer 2012
Page 4
CI
F
CI
H
H
C
C
C
C
H
H
CI
H
CI
When HCl is reacted with 1-pentene, two different products are possible. Which of the
following statements best explains why 2-chloropentane is the major product of this
reaction and 1 -chloropentane is the minor product?
a. The tertiary carbocation intermediate is more stable than the secondary carbocation
intermediate.
b. The tertiary carbocation intermediate is more stable than the primary carbocation
intermediate.
c. The secondary carbocation intermediate is more stable than the primary carbocation
intermediate.
14.
The boiling points for the following compounds are (in no particular order): 36°C, 80°C,
117°C and 141 °C. Which of the compounds (a-d) boils at 80°C?
a. 2-butanone
b. 1-butanol
c. propanoic acid
d. pentane
Summer 2012
Pages
CHEMISTRY 104
Hour Exam II
15.
Which of the following aromatic compounds will be significantly more soluble in
1 M H C l than in pure water?
a. benzaldehyde
16.
b. benzoic acid
c. phenol
d. aniline
e. toluene
The molecule below is a portion of angiotensin I I , a hormone which is present in blood
plasma that regulates blood pressure. Which of the following functional groups is not
present in the molecule?
O
H2N
O
O
CH
-NH
CH-
CH2
CHn
H,C
CH
COOH
CHo
CH
C
NH
-NH
CHCH.
CH,
OH
17.
a. a carboxylic acid
b. a ketone
d. a primary amine
e. an alcohol
c. an amide
A postal employee discovered that an unlabeled bottle in a package is leaking a colorless
liquid and has called you to analyze it. You run several tests on the liquid with the
following results.
Test
Result
Addition of CI2
pH of aqueous solution
Addition of H2Cr04
no reaction
pH = 7
no reaction
Which of the following compounds could be the liquid?
a. hexanal
b. 2-propanone
d. 1-pentene
e. ethanoic acid
c.
1-butanol
Summer 2012
Page 6
CHEMISTRY 104
Hour Exam I I
18.
Which of the following compounds can form hydrogen bonding interactions with itself?
a.
b.
c.
d.
e.
19.
ethyl methyl propyl amine
diethyl ether
propanal
propylethanoate
None of the above compounds can H-bond with itself.
Below is a plot of vap^or pressure vs. temperature for two different substance A and B.
Temperature
Which of the following statements is false concerning this plot?
a.
b.
c.
d.
20.
As temperature increases, the vapor pressure of substance B increases.
Substance A has stronger intermolecular forces than substance B.
Substance A has a lower normal boiling point than substance B.
For substance A, the boiling point at 2 atm external pressvire is higher than the boiling
point at 1 atm external pressure.
Consider the following initial rate data for the reaction:
Cl2(aq) + 2 Fe^^(aq)
2 Fe'^(aq) + 2 Cr(aq)
[Cl2]o (mol/L)
[Feno(mol/L)
0.10
0.50
0.10
0.60
0.50
0.30
0.10
0.40
1.00
0.40
Initial Rate (mol/L»s)
1.8
3.0
2.4
36.0
12.0
Which of the following is the correct rate law for this reaction?
a. rate = k [ C l 2 f
b.
d. rate = k[Cl2][Fe^1^
e. rate = k[Cl2]^ [Fe^l
rate = k[Fe^^]^
c. rate = k[Cl2][Fen
CHEMISTRY 104
Hour Exam I I
21.
Summer 2012
Page?
Consider the following initial rate data for the reaction:
2NO(g) -f Br2(g) -> 2N0Br(g)
Experiment
[N0]o
(mol/L)
[Brijo
(mol/L)
Initial Rate
(mol/L-s)
0.10
0.10
0.20
0.30
0.10
0.20
0.10
0.20
12
24
48
?
1
2
3
4
What is the initial rate for experiment 4?
a.
22.
192mol/L*s
b. 144mol/L*s
d. 108mol/L*s
e) 216mol/L*s
c. 96 mol/L*s
The reaction
A
B + C
is second order in A. When [A]o= 0.100 M , the reaction is 20.0% complete in 40.0
minutes. Calculate the value of the rate constant in units of L/mol»min.
a. 6.25x10"^
23.
b. 5.58x10'^
c.
16.0
d. 1.00
e.
16.0
Consider the reaction:
2A -> D
Concentration of A vs time data is collected. I f a plot of [A] versus time is linear, then
the reaction is
order in A and the slope of the straight line in the plot is equal to
a. zero; k
b. first; k
d. zero; - k
e. first; - k
c. second; k
CHEMISTRY 104
Hour Exam II
24.
Summer 2012
Pages
Consider the following general reaction mechanism:
A + B
C
C + D ~> E + F
E -f A
B + G
For the overall reaction, B is a
a.
b.
c.
d.
e.
25.
26.
reactant;
product;
catalyst;
reactant;
catalyst;
and C is a(an)
product
intermediate
product
intermediate
intermediate
E a is a symbol used to designate activation energy. One of the characteristics of catalyzed
reactions is that:
^-
E a , forward ~ E a , reverse
b.
E a , catalyzed ~ E a , uncatalyzed
C.
AHcatalyzed ~ AHuncatalyzed
e.
E a , catalyzed
E a , uncatalyzed
Which of the following statements is true?
a. An increase in temperature decreases the rate of a forward reaction.
b. At higher temperatures, collisions between gaseous reactants are more effective in
converting reactants to products.
c. All collisions between reactant molecules result in product formation.
d. The orders in a rate law always equal the coefficient in the balanced reaction.
e. A catalyzed reaction at equilibrium produces more product than an uncatalyzed
reaction at equilibrium.
27.
In a reaction, increasing the concentration of a reactant by a factor of 4 causes the rate of
reaction to increase by a factor of 64. What is the order of this substance in the rate law?
a. 0
b. 1
c. 2
d. 3
e. 4
CHEMISTRY 104
Hour Exam II
28.
Summer 2012
Page 9
For the reaction 2 N205(g)
4 NOiCg) + 02(g), the following data were collected:
time (minutes)
fNiOgI (mol/L)
0
10.0
20.0
30.0
40.0
50.0
70.0
1.240x
0.919 X
0.681 X
0.504 X
0.373 X
0.277 x
0.152 x
10"^
10"^
10"^
10"^
10"^
10"^
10"^
(12 pts)
Assume this reaction is either zero, first, or second order in N2O5. Determine the order of
the reaction with respect to N2O5, then answer the following questions.
a. Calculate the half-life for this experiment.
b. Calculate the initial rate of the reaction for this experiment.
c. The activation energy for this reaction is 250 kJ and A E for this reaction is 150 kJ.
Sketch the energy profile (energy versus reaction progress) for this reaction showing
the activation energy, E a , and A E on your plot.
d. Determine the activation energy for the reverse reaction.
CHEMISTRY 104
Hour Exam II
29.
Summer 2012
Page 10
The reaction r (aq) + OCr (aq)
following mechanism:
OCr +
r
H2O
^
+ HOCl
HOI + OH" — ^
IO~(aq) + CP (aq) is believed to occur by the
*• HOCl + OH" fast equilibrium
HOI + c r
slow
H2O + 10" fast
Derive the rate law for this reaction from the mechanism.
(6 pts)
CHEMISTRY 104
Hour Exam I I
30.
Summer 2012
Page 11
Sulfur exhibits two solid forms, rhombic and monoclinic. The complete phase diagram
for sulfur is shown below. Consider the phase diagram when answering the following
questions.
(10 pts)
if!
u
Temperaturc
a. What is the normal melting point of monoclinic sulfur?
b. How many triple points are in the phase diagram?
c. Which is the densest phase?
d. At a pressure of 1.0 x 10 ^ atm, can rhombic sulfur sublime?
e. The pressure on a sample of sulfur at lOO^C is increased from 0 atm to 2000 atm.
What phase changes will occur in this sample of sulfur as the pressure is increased?
CHEMISTRY 104
Hour Exam I I
Summer 2012
Page 12
31.
The following compounds can be produced in a single step reaction. Indicate which
reactants (including catalysts) are necessary to make the desired products. Only major
products should be produced. For the organic reactant compound(s), draw the
structural formula(s) and name it(them). Make sure your structural formulas
contain all hydrogen atoms, e.g., butane should be drawn as CH3CH2CH2CH3 or
CH3-CH2-CH2-CH3, not C-C-C~C.
(15 pts)
a.
ethyl butanoate
b.
chlorobenzene
c.
2,2-dichloropropane
d.
-> hexanoic acid
e.
2-pentanol
CHEMISTRY 104
Hour Exam II
32.
Summer 2012
Page 13
When H2O is reacted with cyclobutene (in the presence of H"^), an alcohol is produced.
Propose a detailed mechanism for this reaction. Make sure your structures include all
hydrogen atoms and lone pair electrons.
(9 pts)
33.
a. How many ketones have the formula C5H10O?
(6 pts)
b. Name the structural isomer of C5H12 which has the lowest boiling point.
c. Draw the structural formula for the isomer of C4H10O which is optically active.
CHEMISTRY 104
Hour Exam I I
34.
Summer 2012
Page 14
A student performed the following multistep conversions, taking the initial organic
compound through several reactions. Assume the organic product after each reaction is a
major product, which then becomes the reactant organic molecule in the next step. Draw
the formula for the major organic product in each step. To save time you may omit the
hydrogens attached to the carbon atoms in your structure.
(14 pts)
a. 3-methyl-3-penten-2-ol = initial organic compound
Step ' l : Reaction with H2/Pt
Step 2: Reaction with H""
Step 3: Reaction with HBr ->
b. butanoic acid = initial organic compound
Stepl: Reaction with LiAlH4/H20
Step 2: Reaction with H^
Step 3: Reaction with H20/H^
Step 4: Reaction with H2Cr04 ->