Download last year`s April exam

CHEMISTRY 150
April 2013
Dr. B. MacLean
NAME: (please print) ___________________________________
ID #: ___________________________________
This is a three hour exam.
Read over the entire exam before beginning, and begin by doing those questions which you find easiest. Ration your time according
to the value of each question.
There should be 16 pages in this exam (including this page). If your exam copy does not have 16 pages, notify me immediately.
Answer all parts of this exam as indicated. For multiple choice questions, use the data card provided and hand this card in with your
exam when you are finished. Be sure to indicate your name and ID number on this card and the exam. It is your responsibility to
ensure that all of your answers are legible.
READ ALL QUESTIONS CAREFULLY
Questions
Out of
A1-30
30
B1
6
B2
4
B3
5
B4
12
B5
14
B6
5
B7
14
B8
10
TOTAL ____________
100
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Section A: Multiple choice - 30 points (1 each): Answer each of the following multiple choice questions on the
computer card provided by shading the letter (a, b, c, or d) that corresponds to the best response in each case.
1) Which of the following compounds would not be considered to be an organic compound?
a) ammonia
b) methane
c) aspirin (ASA)
d) urea ((NH2)2CO)
2) The alpha particle emitted by some radioactive nuclei is identical to the nucleus of a ____________________
atom.
a) hydrogen
b) helium
c) carbon
d) deuterium
3) In terms of the kinds (or types) of organic reactions, alkenes and alkynes undergo mainly
____________________ type reactions, while aromatic compounds undergo mainly ____________________
type reactions.
a) condensation; elimination
b) elimination; substitution
c) addition; condensation
d) addition; substitution
4) Which of the following should possess the highest boiling point?
a) 1,2-ethane diol
b) ethanol
c) 1,2,3-propane triol
d) 2-pentanol
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5) Which of the following types of compounds does not possess an acyl group?
a) alcohol
b) amide
c) ketone
d) ester
6) _______________ are commonly incorporated into perfumes and flavorings.
a) thioethers
b) mercaptans
c) esters
d) alkanes
7) For molecules that possess similar molecular weights, the proper ordering of boiling points (lowest 
highest) would be:
a) alcohol, alkane, aldehyde, amine
b) alkane, amine, aldehyde, alcohol
c) amine, alkane, alcohol, aldehyde
d) alkane, aldehyde, amine, alcohol
8) Which of the following compounds would be expected to be the most basic?
a) ethanamide
b) dimethylamine
c) ethanoate ion
d) ethanol
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9) Which of the following compounds would represent a “free-base” structure?
a)
a)
b)
.HCl
b)
c)
d)
c)
d)
Cl-
10) What kind of constitutional isomerism is possible for alkanes?
a) skeletal
b) positional
c) functional group
d) cis-/trans-
11) The following reaction is known as a:
a) saponification
b) esterification
c) amidification
d) dehydration
H2O
K+
KOH
12) Which of the following acid/base combinations could be used to create a buffer mixture?
a) HCl/NaCl
b) HC2H3O2/NH3
c) HC2H3O3/NaOH
d) NH3/NH4Cl
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13) The reason that two alkenes having the same formula may be stereoisomers is that
a) they possess a  bond between the two double bond carbons
b) -bonds do not allow for free-rotation between two atoms
c) sigma bonds do not allow for free-rotation between two atoms
d) double bonds consist of two  bonds which do not permit twisting
14) One requirement for a carbon atom to be a chiral center is that it must be
a) sp hybridized
b) sp2 hybridized
c) sp3 hybridized
d) involved in a multiple bond
15) Which of the following molecules is chiral?
a) 1-butanol
b) 2-butanol
c) benzene
d) 1-bromopropane
16) From the following list of structures, which one is a hydrocarbon?
a) butanone
b) butyne
c) butanoic acid
d) 2-chloropropane
17) Which of the following compounds would be a carbohydrate?
a)
a)
b)
c)
d)
b)
c)
d)
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18) The neurotransmitters Dopamine and Serotonin are examples of
a) amines
b) amides
c) esters
d) alcohols
19) Which of the following species would be a radical?
a) OHb) OH
c) H2O
d) H3O+
20) When some salt is dissolved into water, it is found that the pH of the solution is neutral. Which of the
following salts might have been dissolved to create this solution?
a) NaF
b) NH4Cl
c) NaBr
d) KC2H3O2
21) Which of the following functional groups cannot form part of a ring in a heterocyclic compound?
a) ester
b) aldehyde
c) amide
d) ether
22) Which of the following structures represents an amino acid?
a)
a)
b)
b)
c)
d)
c)
d)
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23) Which of the following compounds is capable of H-bonding to other molecules like itself?
a) ethers
b) alkanes
c) ketones
d) carboxylic acids
24) Which species shown would be expected to exhibit the greatest water-solubility?
a) hexanoic acid
b) sodium hexanoate
c) hexane
d) hexanol
25) Which of the following acid ionization constants corresponds to the weakest acid?
a) Ka = 1.5 x 10-6
b) Ka = 1.0 x 10-6
c) Ka = 2.0 x 10-3
d) Ka = 1.5 x 10-2
26) Which of the following pKa values describes the strongest acid?
a) pKa = 4.0
b) pKa = 10.0
c) pKa = 2.5
d) pKa = 1.0
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27) The structure shown on the right is a
a) primary amine
b) secondary amine
c) tertiary amine
d) quaternary amine
28) The empirical formula for an alkyne would be
a) CnH2n
b)
CnH2n-2
c) CnH2n-4
d) CnH2n+2
29) Combustion of an alcohol would be expected to yield
a) CO2 and O2
b) CH4 and CO2
c) CO2 and H2O
d) O2 and CH4
30) Two or more forms of an element which differ only in their numbers of neutrons are called
a) isomers
b) isotopes
c) isochromic
d) isostressedout
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Section B: Long-answer problems - 70 points. Answer questions B1-B8.
B1) Sodium hydroxide is used to titrate glutaric acid (IUPAC: pentane dioic acid), a dicarboxylic acid whose
structure is shown below. During the titration, it was found that 25.0 mL of a glutaric acid solution required
15.9 mL of a 1.35 M sodium hydroxide solution to reach the endpoint.
a) Write a balanced equation to describe the titration reaction [2]
b) What is the concentration of the glutaric acid solution? [2]
c) At the endpoint, would you expect the pH of the resulting solution to be acidic, basic, or neutral? [2]
B2) A solution was made up by dissolving ammonia and ammonium chloride into water. The resulting solution
had equal concentrations of NH3 and NH4+ ion. When a strong acid is added to this solution, the concentration
of NH3 was found to drop to 0.50 M while the ammonium concentration became 0.65 M. Ka for ammonium ion
is 5.55 x 10-10.
a) What was the pH of this solution before the addition of the strong acid? [2]
b) What was the pH of the solution after the addition of the strong acid? [2]
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B3a) Selenium-75 (Z=34), a -emitter with a half-life of 120 days, is used medically for pancreas scans.
Approximately how many grams of 75Se would remain from a 0.050 g sample that has been stored for a year?
[2]
b) What nuclide undergoes nuclear fission to produce barium-143, rubidium -94 and three neutrons? [1]
c) List two requirements that must be met in order for a radionuclide to be used in a diagnostic treatment? [2]
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B4) Draw the isomers indicated for each of the following:
a) Draw a positional isomer of 3-methylcyclohexene [2]
b) Draw a functional group isomer of butanone [2]
c) Draw a skeletal isomer of 2,2-dimethylpropane [2]
d) Draw the smallest alkane that has a chiral center. [2]
e) The molecule shown below is called D-ribose, a sugar that is incorporated into the backbone of RNA in
a cyclic form. Draw the enantiomer and a diastereomer of D-ribose. [4]
D-ribose
enantiomer
diastereomer
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B5) Of the following chemical reactions, complete a – d and three of the remaining four (e – h) reactions.
Indicate the structure of the organic product(s) in each case. In cases where a major and minor product is
possible (e.g. for certain addition reactions), only indicate the structure of the major product. [14]
a)
H2O
HCl
HCl
b)
c)
H2O
d)
NaOH
H2SO4
180oC (L.T.)
Br2
e)
f)
g)
h)
FeBr3 (cat)
[R]
NaOH
H+(cat)
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B6a) List the following compounds in order of increasing boiling points: [3]
N-methylpropanamide, butanamide, N,N-dimethylethanamide
(lowest b.p.) _____________________ < _____________________ < _____________________ (highest b.p.)
Answer b) or c) [2]
b) Draw a picture that shows how water molecules can interact with an aldehyde through H-bonding, showing
all possible interactions.
c) Why are aldehydes having short carbon chains are able to dissolve in water, while longer-chain aldehydes are
not water-soluble?
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B7) Provide a name (IUPAC or common names are acceptable) for 7 of the following 8 organic structures
shown below. [14]
Cl-
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B8) A laboratory experiment involving the chemical oxidation of three alcohols was carried out. These
alcohols were labeled “A”, “B”, and “C”, but their actual identities were unknown. When the oxidation
reaction was carried out on each of A, B, and C, it was found that C did not undergo oxidation, but A and B did
(see below). The oxidized products, “D” and “E” were tested with Benedict’s solution. For E, Benedict’s test
yielded a brick-red precipitate, while for D, the reagent remained unchanged. The possible identities of the
alcohols (A – C) are given below. Using this information, draw structures for A - F in the fields indicated.
[10]
Possible starting alcohols: 2-butanol, 2-methyl-2-propanol, 2-methyl-1-propanol
A
[O]
B
C
[O]
D
Benedict's
solution
E
F
Benedict's
solution
[O]
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Formulas, constants
moles _ of _ solute
L _ of _ solution
C1V1  C2V2
M 
pH   log[ H 3O  ]
10  pH  [ H 3O  ]
pH  pK a  log
pK a   log K a 
[ A ]
[ HA]
[ H 3O  ][OH  ]  K w  1x10 14
pH  pOH  14.00
given _ units  desired _ units   desired _ units
 given _ units 
[C ] y [ D] z
K eq 
[ A]w [ B ] x
wA  xB  yC  zD

HA  H 2O  H 3O  A

incr.
priority
B  H 2O  BH   OH 
IUPAC Priority
carboxylic acid
aldehyde
ketone
alcohol
amine
 1 
amount _ remaining  starting _ amount n 
2 
Have a great summer!
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