Sample Exam 4

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 1
1) Name ____________________________________
You are to keep this copy of the test. Your name is in case you leave it behind.
2) Use only a #2 pencil on the answer sheet.
3) Before starting the exam fill in your student ID# (not your SS#). Also fill in your name, course number and sign the
form.
4) Fill in the test form section (A, B, C or D). Which form you have is shown in the upper right corner.
5) Do not begin the exam until you are told to.
6) You will not get your scan sheet back!!! Circle your answers on this exam sheet and then transfer them to the scan
sheet when you are satisfied with all your answers. An answer key will be posted on the class web site and in the
glass case across from the lab after the exam.
7) If atomic weights are needed use only those from the attached periodic table.
8) No scratch paper is to be used. Use the back of this exam sheet if necessary.
9) There are 37 equally weighted questions on this exam. You have 90 minutes to complete them.
10) If you believe there is more than one correct answer pick only the best answer.
Useful Data
Constants
density of H 2 O = 1.00 g/mL
N A (Avogadro’s #) =6.022 x 10 23 particles•mol -1
R (gas constant) = 8.315 J•mol -1 •K -1
1 coulomb • volt = 1 joule
1 ampere = 1 coulomb / second
1 F = 96484.6 C mol -1
Units
2.54 cm = 1 inch
3.78 L = 1 gal
1 kg = 2.20 lb
1 % = 10,000 ppm
1 hr = 60 min
1 min = 60 seconds
1 amu = 1.660540 x 10 -27 kg
molarity (M) = moles solute/L sol’n
molality (m)= moles solute/ kg solvent
Equations
% = fraction • 100 %
ppm = fraction • 10 6 ppm
T (in Kelvin) = 273.15 + T (in ˚C)
T (in Celsius) = (5/9) (T (in F) -32)
ΔG o = -nFE
∆G = G o + RTlnQ
∆G o = -RTlnK eq
Ε o cell = E o cathode - E o anode
o 0.0592
Ecell = E cell - n log Q at 25 o C
o RT
Ecell= E cell - nF ln Q
o
nFE
ln K eq =
cell
RT
o
nE
logKeq =
cell
0.0592
C = nF
at 25 o C
w elec = CE cell = nFE cell
T in K

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 2
1. What is the oxidation state of Chromium in Na 2 Cr 2 O 7 ?
a. +2
b. +3
c. +4
d. +6
e. 0
2. In a voltaic cell, electrons flow from the
a. anode to the cathode.
b. cathode to the anode.
c. anode to the salt bridge.
d. cathode to the salt bridge.
e. the metal surface to the electrolytes
3. The following reaction occurs when zinc is placed in contact with a solution of lead(II) ions:
Zn(s) + Pb 2+ (aq) → Zn 2+ (aq) + Pb(s)
Which one correctly shows one of the half-reactions for the chemical equation above?
a. Pb (s) → Pb 2+ (aq) + 2e -
b. Pb (s) + 2e - → Pb 2+ (aq)
c. Pb 2+ (aq) → Pb (aq) + 2e -
d. Pb 2+ (aq) + 2e - → Pb (s)
e. Pb (s) → Pb 2+ (aq)
4. If the value of E cell is 1.20 V, what is the free energy change associated with the oxidation reduction reaction
involved? Assume that one electron is transferred in this process.
a. 1.16 x 10 5 J/mol
b. 1.20 J/mol
c. -1.20 J/mol
d. -1.16 x 10 5 J/mol
e. 1.20 x 10 5 J/mol
5. _O 2 (g) + _H + (aq) + _Fe(s) → _H 2 O(l) + _Fe 2+ (aq)
What is the correct stoichiometry of the equation above?
a. 1,4,2,2,2
b. 2,3,1,1,8
c. 1,14,2,1
d. 1,2,4,2,2
e. 1,4,1,2,1

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 3
6. In attempting to balance a redox reaction, a student came up with the following half reactions:
Cr 2 O 7
2- + 14H + + 6e- → 2Cr 3+ + 7H 2 O
SO 4
2- + 4H + + 2e - → H 2 SO 3 + H 2 O
There seems to be a problem in adding these two reactions together. What advice or hint would you give to this
student?
a. Multiply all balancing coefficients in the second reaction by 4.
b. Just add the reactants to reactants and products to products.
c. The individual half reactions are not balanced correctly.
d. These are both reduction reactions.
e. There must be a salt bridge in these equation.
7. Using the following data, determine the value of E o cell for the electrochemical cell constructed using the following
reaction, where zinc is the anode and lead is the cathode:
Zn(s) + Pb 2+ (aq) –––> Zn 2+ (aq) + Pb(s)
Half Reaction
Zn 2+ (aq) + 2e - → Zn(s)
Pb 2+ (aq) + 2e - → Pb(s)
E o red (V vs. SHE)
-0.763 V
-0.126 V
a. 0.637 V
b. -0.637 V
c. 1.274 V
d. -1.274 V
e. 0.763

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 4
8. Consider the following diagram
Half Reaction
Cu 2+ (aq) + 2e - → Cu(s)
Cd 2+ (aq) + 2e - → Cd(s)
E o red (V vs. SHE)
0.3419 V
-0.403 V
The direction of the electron flow is____________.
a. from anode to cathode through voltometer, so it flows from Cu electrode to Cd electrode.
b. from cathode to anode through voltmeter, so it flows from Cd electrode to Cu electrode
c. from anode to cathode through voltometer, so it flows from Cd electrode to Cu electrode
d. from cathode to anode through voltometer, so it flows from Cu electrode to Cd electrode
e. fom cathode to anode, through voltomer so it flows from Cu +2 to Cu electrode
9. An electrochemical cell is constructed with a zinc metal anode in contact with a 0.052 M solution of zinc(II) nitrate
and a silver cathode in contact with a 0.0042 M solution of silver(I) nitrate. What is the EMF of this cell at 5ºC?
Metal/metal ion
Eº red (V vs SHE)
silver/silver(I) 0.799
zinc/zinc(II) -0.762
Useful Information: 2Ag + (aq) + Zn(s) --> Zn 2+ (aq) + 2Ag(s)
a. 1.657 V
b. 1.465 V
c. 1.561 V
d. 1.502 V
e. 1.145 V
Generating EPSF... Sheet #1 Layer #1 X: 5.53in Y: 3.80in
99 050 %
%

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 5
10. An electrochemical cell is constructed based on the oxidation of zinc by silver nitrate to make silver and zinc nitrate.
Locate the silver nitrate on the diagram.
11. Calculate the equilibrium constant K eq of the reaction,
O 2 (g) +4H + (aq) + 4Fe 2+ (aq) --> 4Fe 3+ (aq) +2H 2 O, using the following information and the Nernst equation.
Reductioin: O 2 (g) +4H + (aq) + 4e - --> 2H 2 O E o red = +1.23 V
Oxidation: 4Fe 2+ (aq) --> 4Fe 3+ (aq) + 4e - E o red = +0.77 V
a. 31
b. 0.46
c. 1.84
d. 0.0032
e. 1 x 10 31
12. A spontaneous redox reaction has
a. a negative value of E cell and a negative value of ΔG.
b. a positive value of E cell and a positive value of ΔG.
c. a negative value of E cell and a positive value of ΔG.
d. a positive value of E cell and a negative value of ΔG.
e. a value of E cell based on 25 o C
13. Does pH have an effect on the E cell value of the following oxidation-reduction reaction?
5 Fe 2+ (aq) + MnO 4 - (aq) + 8H + (aq) →
5 Fe 3+ (aq) + Mn 2+ (aq) + 4 H 2 O(l)
a. Yes. E cell values for all redox reactions have a dependence on pH.
b. Yes. E cell values for redox reactions involving the proton have a dependence on pH.
c. No. E cell values for redox reactions depend only on the major species in the reaction-in this case, Fe 2+ , MnO 4- ,
Fe 3+ and Mn 2+ .
d. No. E cell values for redox reactions depend on concentrations and temperatures, but not on pH.
e. No. E cell values for the redox reaction depends on the equilibrium constant, K eq
14. How long would it take to electroplate a flute with 28.3 grams of silver at a constant current of 2.0 amps using
AgNO 3 ?
a. 211 minutes
b. 422 minutes
c. 844 minutes
d. 1688 minutes
e.56.6 minutes

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 6
15. A NiMH battery uses the following electrochemical reaction:
NiO(OH)(s) + MH(s) → Ni(OH) 2 (s) + M(s) in KOH (aq)
E o cell =1.32 V
When recharging this battery, one of the possible half reactions is 2H + (aq) + 2e - → Η 2 (g),. This reaction is
unlikely to happen. Why?
a. because of the overpotenial, the gas forming at the electrode needs higher than normal E o red.
b. because Nickel must be oxided to +4.
c. because the solution is basic
d. a and c
e. a, b and c
16. In the electrolysis of H 2 O that contains NaI (aq), which reaction(s) below will happen when 9.0V are applied?
E o red (V)
1. 4H 2 O (l) + 4e - → 2H 2 (g) + 4OH - (aq) -0.8277
2. Na + (aq) + e - → Na(s) -2.714
3. 2H 2 O(l) → Ο 2 (g) + 4H + (aq) + 4e - 1.229
4. 2I - (aq) → I 2 (s) + 2e - 0.535
a. 1
b. 2
c. 1 and 2
d. 1 and 4
e. 1, 3, and 4
17. What is an advantage of fuel cells compared to combustion-based energy sources?
a. The efficiency is higher.
b. It utilizes the “clean”energy source such as fusion.
c. Hydrogen is readily available from a metal hydride ore.
d. a and b
e. a, b and c
18. How much energy can a Zn/Cu voltaic cell produce if you have 65.0 g of Zn? Assume only the following reaction
is taking place.
Zn(s) + Cu 2+ (aq) → Zn 2+ (aq) + Cu(s) E o cell = 1.1V
a. 1.1 x 10 5 J
b. 2.1 x 10 5 J
c. 9.59 x 10 4 J
d. 1.91 x 10 5 J
e. 2.2 J

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 7
19. The figure below depicts a possible anti-rust coating(Zinc, Zn) on the Iron (Fe) metal. Does the anti-rust coating
really work? Choose the answer and statement that best describes the reason.
Zn 2+ (aq) + 2e - → Zn(s)
Fe 2+ (aq) + 2e - → Fe(s)
E o red (V)
-0.763 V
-0.440 V
a. No. Becuase Zn has a lower reduction potential, so it actually helps Fe to rust faster.
b. No. Because Zn has a higher reduction potential, but it doesn’t make any difference.
c. Yes. Becuase Zn has a higher reduction potential, so it actually works.
d. Yes. Because Zn has a lower reduction potential than Fe, so it oxidizes before Fe.
e. Both metals will rust at a same time with a presence of water.
20. What disadvantages are there to the use of hydrogen fuel cells instead of gasoline in vehicles?
a.difficulty of storage of hydrogen
b. no distribution network of hydrogen fuel in place
c. Hydrogen fuel must be produced at the expense of another energy source.
d. a and b
e. a, b and c
21. A typical Lead-Acid automotive battery produces about 12 Volts. The E o cell for Pb/H 2 SO 4 battery is 2.0 V. How
do automotive batteries achieve the 12Volts output?
a. By stacking many cells within the battery case.
b. By using 6 times the concentration of the electrolytes.
c. By increasing the temperature of the cell while the car is driven.
d. a and b
e. a, b and c
22. Copper(II) oxide was reduced to copper metal at high temperatures in ancient refining processes by
a. CO(g)
b. CO 2 (g)
c. O 2 (g)
d. C (g)
e. N 2 (g)

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 8
23. Copper samples have varying degrees of hardness that depend upon
a. the dimensions of its unit cell
b. the predominant isotope in the sample
c. the density of the atoms in the unit cell
d. the number of intersecting line defects in the lattice
e. which type of unit cell the lattice is made from
24. Iron oxide is smelted to form metallic iron according to the following chemical reaction:
Fe 2 O 3 (s) + 3CO(g) ––––> 2Fe(l) + 3CO 2 (g).
What is the change in oxidation number of iron during this process?
a. +2 b. +3 c. -2 d. -3 e. +1
25. The higher the carbon content in steel
a. the stronger and more malleable it is.
b. the stronger and more brittle it is.
c. the weaker and more malleable it is.
d. the weaker and more brittle it is.
e. the weaker and more ductile it is.
26. Stainless steel is less susceptible to rusting than iron because
a. it is coated with plastic.
b. the carbon within the alloy polymerizes to form a protective film.
c. the silicon within the alloy oxidizes to form a protective silicate layer.
d. any iron that oxidizes is rapidly reduced by the other metals in the alloy.
e. other metals than iron in the alloy are oxidized more easily than iron forming protective oxides.
27. Which physical property below is NOT characteristic of metals?
a. they are shiny (high luster)
b. they are good electrical conductors.
c. they are thermal insulators.
d. they are malleable.
e. they are ductile.
28. Aluminum is prepared by
a. smelting with CO at very high temperatures
b. driving off oxygen from the oxide Al 2 O 3 at 2240 ˚C.
c. reaction with perchloric acid, which neutralizes the oxide ion in Al 2 O 3 .
d. electrolysis of Al 2 O 3 dissolved in molten cryolite
e. reaction of Al(CN) 3 with Zn to reduce the Al 3+ to Al.
29. One common iron containing mineral is known as “fool’s gold” or iron pyrite. The chemical formula for this
mineral is FeS 2 . What is the % by mass of iron in fool’s gold? Iron pyrite is not usually used as a source of iron,
but it could be.
a. 46.547%
b. 0.466%
c. 2.1484%
d. 87.081%
e. 26.726%

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 9
30. A ceramic is
a. a chemically resistant and heat-resistant solid produced by heating compounds containing cerium.
b. a chemically resistant and heat-resistant solid produced by heating clays.
c. a chemically resistant and heat-resistant solid produced by heating sand and water.
d. a chemically resistant and heat-resistant solid produced by heating any compounds containing aluminum and
sulfur.
e. a chemically resistant and heat-resistant solid produced by heating clays in a reducing atmosphere.
31. The band gap
a. in metals is large, in semiconductors is small and in insulators is zero.
b. in metals is small, in semiconductors is large and in insulators is zero.
c. in metals is zero, in semiconductors is large and in insulators is small.
d. in metals is small, in semiconductors is zero and in insulators is large.
e. in metals is zero, in semiconductors is small and in insulators is large.
32. A silicon sample is doped with P. It is a
a. p-type semiconductor with an excess of electrons.
b. n-type semiconductor with a deficiency of electrons.
c. p-type semiconductor with a deficiency of electrons.
d. n-type semiconductor with an excess of electrons.
e. n-p-type semiconductor which will generate electricity when exposed to light.
33. Doping is used in photovoltaic cells to
a. control the color of light that is absorbed.
b. provide an emf to push electrons through the circuit and shrink the band gap to increase the absorption of
longer wavelength light.
c. provide a use for silicon that is too impure for use in electronics.
d. increase the band gap to reduce the absorption of longer wavelength light and provide an emf to push
electrons through the circuit.
e. provide the electrons necessary for current to flow in the external circuit.

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 10
34. The most commonly recycled plastics are
O O
–CH 2
–CH 2
–O–C– –C–O–
n
Polyethylene terephthalate (PET)
–CH 2
–CH 2
–
n
Low and high density polyethylene (LDPE,HDPE)
–CH–CH 2
–
n
–CH–CH 2
–
n
CH 3
Polypropylene (PP)
–CH–CH 2
–
n
Cl
Polyvinyl chloride (PVC)
Which of the above polymers is NOT an addition polymer?
a. PET
b. LDPE/HDPE
c. PP
d. PS
e. PVC
35. Polymers that have significant inter-chain hydrogen-bonding interactions
a. repel water and form weak fibers.
b. repel water and form strong fibers.
c. absorb water and form weak fibers.
d. absorb water and form strong fibers.
e. none of the above.
Polystyrene (PS)

Chemistry 106: General Chemistry II
Exam 4 Form A
Dr. Gutow and Dr. Matsuno Fall 2004
Page 11
36. Consider the common synthetic polymers below.
O O
–CH 2
–CH 2
–O–C– –C–O–
n
Polyethylene terephthalate (PET)
–CH 2
–CH 2
–
n
Low and high density polyethylene (LDPE,HDPE)
–CH–CH 2
–
n
–CH–CH 2
–
n
CH 3
Polypropylene (PP)
–CH–CH 2
–
n
Cl
Polyvinyl chloride (PVC)
Which ones will form the least elastic fibers?
a. PET and PP
b. PET and PS
c. LDPE, HDPE and PP
d. PP and PVC
e. PS and PP
37. Large crystalline domains in polymers lead to
a. weaker stiff polymers.
b. more elastic soft polymers.
c. stronger stiff polymers.
d. weaker soft polymers.
e. more elastic stiff polymers.
Polystyrene (PS)