Download 2010 Fall Final key

CHEMISTRY 1A
Fall 2010 Final Exam Key
YOU MIGHT FIND THE FOLLOWING USEFUL;
H°  E°  ( n)RT
R=
0.008314 kJ
K • mol


0.00418 kJ
q   C cal 
m w  T

g C


Hrxn =  Hf (products) −  Hf (reactants)
Electronegativities
H
2.2
Li
0.98
Be
1.57
B
2.04
C
2.55
N
3.04
O
3.44
F
3.98
Na
0.93
Mg
1.31
Al
1.61
Si
1.9
P
2.19
S
2.58
Cl
3.16
K
0.82
Ca
1.0
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Rb
0.82
Sr
0.95
In
1.78
Sn
1.96
Sb
2.05
Te
2.1
I
2.66
Cs
0.79
Ba
0.89
Tl
2.33
Pb
2.02
Bi
2.0
Po
2.2
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Xe
2.6
Answer the following by writing the word, words, letter, letters or number in each blank
that best completes each sentence. (1 point each blank)
1. The elements in group 17 on the periodic table are called halogens.
2. The intermolecular attraction between a nitrogen, oxygen, or fluorine atom of one molecule
and a hydrogen atom bonded to a nitrogen, oxygen, or fluorine atom in another molecule is
called a(n) hydrogen bond.
3. Isomers are compounds that have the same molecular formula but different molecular
structures.
4. The reactant that runs out first and limits the amount of product that can form is called the
limiting reactant.
5. A reaction that involves a rapid oxidation accompanied by heat and usually light is called
a(n) combustion reaction.
6. The gas in a solution of a gas in a liquid, the solid in a solution of a solid in a liquid, or the
minor component in other solutions is called a(n) solute.
7. A(n) strong electrolyte is a substance that ionizes or dissociates completely in an aqueous
solution.
8. A(n) strong acid is an acid that donates its Hions to water in a reaction that goes
completely to products. Such a compound produces close to one H3Oion in solution for
each acid molecule dissolved in water.
9. Any chemical change in which at least one element loses electrons, either completely or
partially is called oxidation.
10. Potential energy is a retrievable, stored form of energy an object possesses by virtue of its
position or state.
11. A(n) exothermic change is a change that leads to heat energy being released from the
system to the surroundings.
12. A(n) cis isomer is a structure that has like groups on different carbons (which are linked by
a double bond) and on the same side of the double bond.
13. Hydrogenation is a process by which hydrogen is added to an unsaturated triglyceride to
convert double bonds to single bonds. This can be done by combining the unsaturated
triglyceride with hydrogen gas and a platinum catalyst.
14. A polar molecule or ion (or a portion of a molecule or polyatomic ion) that is attracted to
water is called hydrophilic.
15. A(n) catalyst is a substance that speeds a chemical reaction without being permanently
altered itself.
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16. A(n) peptide bond is an amide functional group that forms when the carboxylic acid group
on one amino acid reacts with the amine group of another amino acid.
17. A(n) disulfide bond is a covalent bond between two sulfur atoms of two different amino
acids in a protein molecule.
18. A(n) salt bridge is an attraction between a negatively charged side chain and a positively
charged side chain in a protein molecule.
19. Hydrolysis is a chemical reaction in which larger molecules are converted into smaller
molecules by adding water to their structure.
20. A(n) enzyme is a naturally occurring catalyst.
21. A(n) substrate is a molecule that an enzyme causes to react.
22. A specific section of the protein structure of an enzyme in which the substrate fits and
reacts is called a(n) active site.
23. A(n) condensation (or step-growth) polymer is a polymer formed when small molecules,
such as water, are released in its formation. This category includes nylon and polyester.
24. A(n) free radical is a molecule with an unpaired electron.
25. The disaccharide sucrose is composed the monosaccharides glucose and fructose.
26. In digestion, proteins are converted into amino acids.
27. Using the skeleton below, draw a Lewis structure for CH3CH2CONHCH3. Draw all the
resonance structures and the resonance hybrid. Show all formal charges. (6 points each)
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28. Identify each of the following as a binary covalent compound, a binary ionic compound,
a binary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a
sugar. Write name for each. (8 points)
Chemical Formula
Type of Substance
Name
BrF5
binary covalent
bromine pentafluoride
Ni(H2PO2)2
ionic with polyatomic ion
nickel(II) dihydrogen phosphite
H2SO4
oxyacid
sulfuric acid
HF(aq)
binary acid
hydrofluoric acid
29. Identify each of the following as a binary covalent compound, a binary ionic compound,
a binary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a
sugar. Write formula for each. (8 points)
Chemical Formula
Type of Substance
Formula
iron(III) sulfide
binary ionic
Fe2S3
nitrous acid
oxyacid
HNO2
methanol
alcohol
CH3OH
sucrose
sugar
C12H22O11
30. Identify each of the following as (1) a strong, weak, or nonelectrolyte and (2) a strong acid,
weak acid, strong base, weak base, or neutral. (1 point each box)
Substance
Strong, weak, or nonelectrolyte
Strong acid, weak acid, strong
base, weak base, or neutral
ammonia
Weak electrolyte
Weak base
HNO3(aq)
Strong electrolyte
Strong acid
phosphoric acid
Weak electrolyte
Weak acid
NaNO2
Strong electrolyte
Weak base
sodium hydrogen sulfate Strong electrolyte
Weak acid
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31. Write the complete equation, the complete ionic equation, and the net ionic equation for
the neutralization reaction that takes place between the following reactants. (8 points)
Zn(OH)2(s) + 2HC2H3O2(aq) Zn(C2H3O2)2(aq) + 2H2O(l)
Zn(OH)2(s) + 2HC2H3O2(aq)Zn(aq) + 2C2H3O2(aq) + 2H2O(l)
Zn(OH)2(s) + 2HC2H3O2(aq)Zn(aq) + 2C2H3O2(aq) + 2H2O(l)
32. Ethanethiol, CH3CH2SH(g), is a very foul-smelling substance used to odorize natural
gas. Write a complete, balanced equation for its combustion. (4 points)
CH3CH2SH(g) + 9/2O2(g)  2CO2(g) + 3H2O(l) + SO2(g)
Or 2CH3CH2SH(g) + 9O2(g)  4CO2(g) + 6H2O(l) + 2SO2(g)
33. For each of the following, write the type of particle (atoms, molecules, ions, etc.) that
form the fundamental structure of the substance, and write the name of the type of
attraction holding these particles in the solid and liquid form. Indicate the formula in
each pair that represents the substance that you would expect to have the stronger
attractions that hold the particles in the liquid or solid form. (4 points each)
a. 2-propanol, CH3CH(OH)CH3
type of particles CH3CH(OH)CH3 molecules
type of attraction hydrogen bonds and London forces
or butane, CH3CH2CH2CH3
type of particles CH3CH2CH2CH3 molecules
type of attraction London forces
stronger attractions CH3CH(OH)CH3
b. ammonium nitrate, NH4NO3
type of particles NH4 and NO3 ions
type of attraction ionic bonds
or glucose, C6H12O6
type of particles C6H12O6 molecules
type of attraction hydrogen bonds and London forces
stronger attractions NH4NO3
c. butanal, CH3CH2CH2CHO
type of particles CH3CH2CH2CHO molecules
type of attraction dipole-dipole forces and London forces
or octanal, CH3(CH2)6CHO
type of particles CH3(CH2)8CHO molecules
type of attraction dipole-dipole forces and London forces
stronger attractions CH3(CH2)8CHO
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34. Draw the line drawing and condensed formula for the Lewis structure below. Classify it
as an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone,
ether, ester, amine, or amide. (6 points)
aldehyde
CH3CH(CH3)CHO
35. Draw the Lewis structure and condensed formula for the line drawing below. Classify it
as an alkane, alkene, alkyne, arene (aromatic), alcohol, carboxylic acid, aldehyde, ketone,
ether, ester, amine, or amide. (6 points)
ether
CH3CH2OCH(CH3)CH3
36. Draw the structure of the tripeptide that forms from linking the amino acids tryptophan,
aspartic acid, and asparagine. (4 points)
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35. Look at the front screen in the lecture hall and answer the following questions.
(1 point each)
a. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? alcohol
b. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? aldehyde
c. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? carboxylic acid
d. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? ether
e. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? ester
f. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? alkyne
g. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? amine
h. Does this image represent an alkane, alkene, alkyne, arene (aromatic), alcohol,
carboxylic acid, aldehyde, ketone, ether, ester, amine, or amide? amide
i. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a
protein), a protein, or a steroid? peptide
j. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a
protein), a protein, or a steroid? amino acid
k. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a
protein), a protein, or a steroid? steroid
l.
Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a
protein), a protein, or a steroid? triglyceride
m. Does this image represent a carbohydrate, a triglyceride, an amino acid, a peptide (not a
protein), a protein, or a steroid? protein
n. Does this image represent glucose or fructose? fructose
o. Does this image represent -glucose or-glucose? glucose
p. Is the linkage shown in this structure an (14) linkage or a (14) linkage?
(14)
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43. Consider the following Lewis Structure for CH2CHCHO. (8 points)
What is the hybridization for the far left carbon atom? sp2
What is the hybridization for the far right carbon atom? sp2
What is the hybridization for the oxygen atom? sp2
Write a description of the bonding, stating whether each bond is sigma, pi, or part of
a delocalized pi system and by stating which atomic orbitals overlap to form the
bonds.
From left to right:
2  H-C bonds due to 1s-sp2 overlap
1  C-C bond due to sp2-sp2 overlap
1  C-C bond due to p-p overlap
1  C-C bond due to sp2-sp2 overlap
1  C-O bond due to sp2-sp2 overlap
1  C-O bond due to p-p overlap
1  C-H bond due to sp2-1s overlap
What is the name of the electron group geometry around each carbon atom?
trigonal planar
Draw a sketch with bond angles.
For the following calculations, be sure to show your work and round your final answer off
correctly. NOTE: Remember that there is part credit for each problem. Even if you
cannot do all of a problem, be sure to set up as much of it as you can.
44. If 21.8 mL of 0.505 M NaOH is required to neutralize 25.00 mL of a phosphoric acid,
H3PO4, solution, what is the molarity of the phosphoric acid? (6 points)
? mol H3PO4
21.8 mL NaOH soln  0.505 mol NaOH   1 mol H3PO4   103 mL 
=




L H3PO4 soln 25.00 mL H3PO4 soln  103 mL NaOH soln   3 mol NaOH   1 L 
= 0.147 M H3PO4
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45. Acetic acid, CH3CO2H, can be made from methanol and carbon monoxide in the
following reaction, which uses a rhodium/iodine catalyst. What is the percent yield when
513 kg of liquid CH3CO2H form from the reaction of 309 kg of CH3OH with 543 m3
of CO(g) at 1 atm and 175 C? (8 points)
CH3OH + CO  CH3CO2H
 1  60.053 kg CH3CO2 H 
? kg CH3CO2 H = 309 kg CH3OH 
 = 579 kg CH3CO2H
 1  32.042 kg CH3OH 
  1 atm 
 103 L  
K g mol
? kg CH3CO2 H = 543 m CO 




3
 1 m   0.082058 L g atm   448 K 
 1 mol CH3CO2 H   60.053 g CH3CO2 H   1 kg 

  1 mol CH CO H   103 g 
1 mol CO


3
2


3
= 887 kg CH3CO2H
% yield =
513 kg CH3CO2 H
actual yield
 100 = 88.6% yield
× 100 =
theoretical yield
579 kg CH3CO2 H
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Answer the following in short answer form.
41. Explain why lowering the temperature of a gas and why increasing the concentration of a
gas by adding gas to a container or decreasing the available volume leads to a greater
difference between the pressure calculated from the ideal gas equation and the real or
measured pressure. (8 points)
46. Explain why enzyme act on specific substances and form specific products. (6 points)



The active site of each enzyme has a physical shape that only allows certain
substrates to fit into it.
Binding groups attract specific substrates to the active site, which is the portion of
the enzyme where the reaction occurs. The orientation of these groups fit certain
groups on certain substrates so that the substrates are placed in the correct
orientation to react.
Catalytic groups stabilize the intermediates and therefore speed reactions. The
orientation of these groups also fit certain groups on certain substrates.
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