# Practice Exam I

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```					Practice Exam II
Dr. Miller
Spring 2004

_____1) The mass of 3717Cl is 36.96590 amu. The binding energy per nucleon of 3717Cl
is: (Use the following masses: 11H = 1.00783 amu; 10n = 1.00867 amu)

a) 1.41 x 10-12 J/nucleon            b) 5.09 x 10-11 J/nucleon
c) 1.29 x 10-12 J/nucleon            d) 5.08 x 10-8 J/nucleon
e) 1.38 x 10-12 J/nucleon

_____2) A freshly prepared sample of 9039Y undergoes 7.6 x 105 disintegrations per
minute (dpm) at a certain time. Exactly 14 days later, the same sample decays at 1.6 x
104 dpm. The half-life of 9039Y is:

a) 0.20 day                          b) 0.28 days             c) 2.5 days
d) 2.7 days                          e) 14 days

_____3) 23592U undergoes a series of and - decays to stable 20782Pb. How many -
particles and - are emitted in this process?

a) 7, 10-                      b) 14, 10-
c) 28, 10-                     c) 7, 4-
e) 10, 28-

_____4) In fluorine-18 (189F), the neutron-to-proton ratio is too low and this nuclide
undergoes radioactive decay. Which of the following decay processes would be expected
to produce a nuclide with a neutron-to-proton ratio GREATER THAN that for fluorine-
18?

a) alpha decay                   b) beta decay            c) gamma decay (only)

d) positron decay                e) none of these

_____5) Complete and balance the following nuclear equation:
65            4          66
29Cu   +     2He           30Zn   + ?

a) 10n
b) 10n + 11p
c) 2 10n + 11p
d) 3 10n + 11p
_____6) Select the equation below which best represents the nuclear transmutation of
16           13
8O (p,) to 7N.

7N + 4 0n + 2 1
16          1       13         1     0
a)      8O   +    1p 
16          1       13       4
b)      8O   +     0n      7N +    2He
16          1       13       4
c)      8O   +    1p      7N +     2He
7N + 7 1p + 4 -1
16          4          13        1     0
d)      8O   +     2He 

_____7) An archeologist unearths a bone sample and wants to know the age of the bone.
A chemist friend determines that 45.3% of the initial amount of carbon-14 is present in
the bone sample. If the half-life of carbon-14 is 5730 years, calculate the age (in years)
of the bone.

a) 6612 yr                            b) 1.38 x 10-4 yr
c) 9712 yr                            d) 5026 yr

_____8) Which of the following characteristics of particles produced by radioactive
decay are important for assessing the potential for biological damage to living systems?

a) penetrating ability         b) mass               c) kinetic energy
d) charge                      e) all of these

_____9) Thorium-232 (23290Th) decays in a series of steps to produce the unstable
nuclide, radon-220 (22086Rn). Which of the following series of decays would produce

a) 3  + 2 -                  b) 4  + 2 -                 c) 5  + 2 -
d) 2  + 3 -                  e) 1  + 2 -

_____10) The heaviest nuclides become increasingly unstable with increasing atomic (Z)
or mass (A) number because of the:

a) decrease in the surface to volume ratio of the nucleus with increasing A or Z.
b) increase in the surface to volume ratio of the nucleus with increasing A or Z.
c) decrease in the coulomb repulsion between the protons with increasing A or
Z.
d) increase in the coulomb repulsion between the protons with increasing A or Z.
e) increase in the coulomb attraction between protons and electrons with
increasing A or Z.

Dr. Miller                                                                                 2
Practice Exam II
Chem 114
Spring 04
_____11) What is the energy change (in kJ) when 1.00 x 10-9 mol of 5626Fe are
assembled from 11H atoms and neutrons? Use the following masses:
56
26Fe     = 55.9349 amu; 11H = 1.00783 amu; 10n = 1.00867 amu

a) 4.8 x 10-1 kJ                        b) 4.8 x 101 kJ
c) 7.9 x 10-20 kJ                       d) 7.9 x 1020 kJ

_____12) The only stable nuclide with A = 35 is 3517Cl. Which of the following
equations correctly describe the process by which 3515P decays to 3517Cl?

a)   35
15P      35
17Cl   + -           b)   35
15P   + e-        35
16S
35
16S    + e-        35
17Cl

c)   35
15P        35
16Si       + -           d)   35
15P       35
17Cl    + +
35
16Si        35
17Cl      + -

____13) In terms of the collision model of kinetics, which of the following factors BEST
accounts for the fact that not all collisions result in a reaction?

a)   The temperature of the system.
b)   The orientation of the molecules at the moment of collision.
c)   The energy with which the collisions occur.
d)   The activation energy of the complex.
e)   All of these factors are important.

____14) Which of the following statement is ALWAYS TRUE about a catalyst?

a)   A catalyst is a surface phenomenon.
b)   A catalyst increases the temperature of a reaction.
c)   A catalyst decreases the activation energy of the reaction.
d)   A catalyst is consumed in a reaction.
e)   A catalyst does not affect the G of a reaction.

Dr. Miller                                                                                 3
Practice Exam II
Chem 114
Spring 04
____15) The reaction shown below:

2 NO2  2 NO + O2

follows second-order kinetics. Experiments indicate that at 300 oC the concentration of
NO2 drops from an initial value of 0.0100 M to 0.0065 M in 100 seconds. Based on these
data, what is the value of the rate constant, k, at 300 oC?

a)   0.538 M-1s-1
b)   4.23 x 10-3 M-1s-1
c)   4.31 x 10-3 M-1s-1
d)   3.50 x 10-5 M-1s-1
e)   None of these

____16) The exponents n and m in the rate law, rate = k [A]n [B]m, are determined for an
overall reaction by

a)   using the balanced chemical equation
b)   using the subscripts for the chemical formulas
c)   using the coefficients of the chemical formulas
d)   educated guess
e)   experiment

____17) The study of chemical kinetics can provide information about which of the
following?
i.     rates of chemical reactions
ii.    reaction mechanisms
iii.   factors that influence rates of chemical reactions

a)   i only
b)   i and ii
c)   i and iii
d)   ii and iii
e)   i, ii, iii

Dr. Miller                                                                             4
Practice Exam II
Chem 114
Spring 04
____18) Bromine, Br2, is formed in the following reaction:

BrO3- (aq) + 5 Br - (aq) + 6 H3O+ (aq)  3 Br2 (aq) + 9 H2O (l)

If the rate of disappearance of bromide ion, Br -, at a particular moment in time is equal to
3.7 x 10-4 M/s, what is the rate (in M/s) at which Br2 is being produced during this same
time interval?

a)   6.2 x 10-4 M/s
b)   1.1 x 10-3 M/s
c)   6.6 x 10-4 M/s
d)   2.2 x 10-4 M/s

____19) The reaction 2 NO2 + O3  N2O5 + O2 obeys the rate law shown
below:
Rate = k [NO2][O3]
Which of the following mechanisms is consistent with this rate law?

a) NO2 + O3  NO3 + O2                                 (slow)
NO3 + NO2  N2O5                                    (fast)

b) NO2 + NO2  N2O4                                    (fast equilibrium)
N2O4 + O3  N2O5 + O2                               (slow)

c) NO2 + NO2  N2O2 + O2                               (slow)
N2O2 + O3  N2O5                                    (fast)

d) None of these mechanisms are consistent with the above rate law.

____20) The rate constant of a first-order reaction is 4.60 x 10-4 s-1 at 350 oC. If the
activation energy is 104 kJ/mol, at what temperature will the rate constant be 8.80 x 10-4
s-1?

a)   644 oC
b)   402 oC
c)   371 oC
d)   350 oC
e)   183 oC

Dr. Miller                                                                                   5
Practice Exam II
Chem 114
Spring 04
____21) At room temperature, hydrogen peroxide decomposes to form water and oxygen
and is represented by the following equation.

2 H2O2  2 H2O + O2

The reaction is known to be first order; therefore, the slope of the appropriate straight-
line graph is equal to:

a)   1/[A]o
b)   –k
c)   ln[A]o
d)   +k
e)   ln[A]

____22) Consider the bromination of acetone, CH3COCH3, in the presence of acid:

CH3COCH3 (aq) + Br2 (aq) + H+ (aq)  CH3COCH2Br (aq)

And the following initial rate data:

[CH3COCH3] M                 [Br2] M                  [H+] M            Initial Rate M/s
0.30                     0.050                    0.050               5.70 x 10-5
0.30                      0.10                    0.050               5.70 x 10-5
0.30                     0.050                     0.10               1.14 x 10-4
0.60                     0.050                     0.20               4.56 x 10-4
0.60                     0.050                    0.050               1.14 x 10-4

Which of the following is the correct rate law for this reaction?

a)   Rate = k [CH3COCH3][Br2][H+]
b)   Rate = k [CH3COCH3]2[Br2]2[H+]
c)   Rate = k [CH3COCH3][Br2]
d)   Rate = k [CH3COCH3][H+]
e)   Rate = k [CH3COCH3]

Dr. Miller                                                                                   6
Practice Exam II
Chem 114
Spring 04
____23) Calculate the value of the rate constant in problem 19.

a)   13.6
b)   3.41
c)   54.5
d)   0.852
e)   None of these.

____24) The rate constant for the second-order reaction:

2 NOBr (g)  2 NO (g) + Br2 (g)

is 0.800 M-1s-1. Calculate the the half-life of this reaction if after 22.0 seconds, the
concentration of NOBr decreased from an initial concentration of 0.0860 M to a final
concentration of 0.0340 M.

a)   36.8 s
b)   18.4 s
c)   14.4 s
d)   7.25 s

____25) The thermal decomposition of phosphine (PH3) into phosphorus and molecular
hydrogen is the first order reaction shown below:

4 PH3 (g)  P4 (g) + 6 H2 (g)

If the rate constant is 1.98 x 10-2 s-1, how much time is required for 95% of the original
concentration of phosphine to decompose?

a)   186 s
b)   151 s
c)   4800 s
d)   2400 s

____26) For the elementary reaction shown below:

NO3 + CO  NO2 + CO2

a)   the molecularity is 2 and the Rate = k [NO2] [CO2]
b)   the molecularity is 2 and the Rate = k [NO3] [CO]
c)   the molecularity is 4 and the Rate = k [NO3] [CO]
d)   the molecularity is 4 and the Rate = k [NO2] [CO2]

Dr. Miller                                                                                   7
Practice Exam II
Chem 114
Spring 04
____27) The rate of the reaction,

S-2 (aq) + 4 Cl2 (g) + 8 OH- (aq)  8 Cl- (aq) + SO42- (aq) + 4 H2O (l)

Is measured at a particular time and it is found that [S2-] = -2.0 x 10-2 M/s.
t
At the same time, the rate at which Cl- (aq) is formed is:

a)   2.0 x 10-2 M/s
b)   -2.0 x 10-2 M/s
c)   0.16 M/s
d)   -0.16 M/s
e)   2.5 x 10-3 M/s

____28) The catalyzed decomposition of hydrogen bromide, HBr, into the elements H2
and Br2 is believed to involve the following 3-step mechanism:

1) HBr + O2  HBrO + O
2) HBr + O  HBrO
3) 2 HBrO  H2 + Br2 + O2

Which species are the catalyst and the intermediate in this reaction?

a)   Catalyst = O2, HBrO                        Intermediate = O
b)   Catalyst = O2, O                           Intermediate = HBrO
c)   Catalyst = O2                              Intermediate = HBrO, O
d)   Catalyst = O2                              Intermediate = HBrO, HBr, O
e)   Catalyst = O                               Intermediate = O2, HBrO

____29) A particular reaction has a rate constant of 4.41 x 10-3 s-1 at 42 oC and a rate
constant of 9.79 x 10-2 s-1 at 78 oC. Calculate the activation energy in kJ of this reaction.

a)   20
b)   7.9
c)   79
d)   180
e)   none of these

Dr. Miller                                                                                      8
Practice Exam II
Chem 114
Spring 04
____30) At 760 K, acetaldehyde decomposes to form methane and carbon monoxide in a
reaction represented by the following equation:

CH3CHO  CH4 + CO

A plot of ln[CH3CHO] versus time was linear, and the value of k was calculated to be
1.3 x 10-3 s-1. Therefore, how many seconds will it take for the concentration of
CH3CHO to decrease to one-half its initial value of 0.10 M?

a)   7.7 x 103 s
b)   1.1 x 103 s
c)   5.3 x 102 s
d)   2.7 x 102 s
e)   none of these

____31) The rate constant of a first-order reaction, A  2 B, can be obtained from the
slope of the straight line in which of the following plots?

Dr. Miller                                                                               9
Practice Exam II
Chem 114
Spring 04
____32) The following reaction was studied and the data which follows collected:

S2O82- (aq) + 3 I - (aq)  2 SO42- (aq) + I3- (aq)

Experiment              [S2O82-]o (M)            [I -]o (M)          Initial Rate (M/s)
1                      0.080                   0.034                  2.2 x 10-4
2                      0.080                   0.017                  1.1 x 10-4
3                       0.16                   0.017                  2.2 x 10-4

The rate law for this reaction is:

a)   rate = k[S2O82-]2
b)   rate = k[S2O82-] [I -]
c)   rate = k[S2O82-] [I -]2
d)   rate = k[S2O82-]2 [I -]2
e)   rate = k [I -]

____33) Which of the following statements BEST describes the condition(s) needed for
the successful formation of a product according to the collision model?

a) The collision must involve a sufficient amount of energy, provided from the
motion of the particles, to overcome the activation energy.
b) The relative orientation of the particles has little or no effect on the formation
of the product.
c) The relative orientation of the particles has an effect only if the kinetic energy
of the particles is below some minimum value.
d) The relative orientation of the particles must allow for formation of the new
bonds in the product.
e) The energy of the incoming particles must be above a certain minimum value
and the relative orientation of the particles must allow for formation of new
bonds in the product.

____34) The catalyzed pathway in a reaction mechanism has a ________________
activation energy than the uncatalyzed pathway and thus results in a _____________
reaction rate.

a)   higher, slower
c)   higher, faster
d)   lower, slower
f)   lower, faster

Dr. Miller                                                                                10
Practice Exam II
Chem 114
Spring 04
____35) The reaction in which NO2 (g) forms N2O4 (g) is second order in NO2:

2 NO2 (g)  N2O4 (g)
Calculate the value of the rate constant for this reaction if it takes 0.005 seconds for the
initial concentration of NO2 to decrease from 0.50 M to 0.25 M.

a)   1.39 x 102 M-1s-1
b)   4.00 x 102 M-1s-1
c)   5.00 x 101 M-1s-1
d)   4.30 x 10-1M-1s-1

____36) An INCREASE in which of the following will NOT produce an increase in the
rate of a chemical reaction?

a)   activation energy
b)   temperature
c)   reactant concentration
d)   An increase in any of these will increase the rate.
e)   Rate will not be affected by any of these.

____37) Given the following reaction and equilibrium constant, which statement is
correct for this reaction when it is at equilibrium.
CO2  CO + ½ O2              Kc = 9.1 x 10-12

a)   The forward rate of reaction will be the same as the reverse rate of reaction.
b)   The forward rate of reaction will be larger than the reverse rate of reaction.
c)   The forward rate of reaction will be smaller than the reverse rate of reaction.
d)   The concentration of CO2 must be smaller than the concentrations of both CO
and O2.

____38) Consider the following reaction mechanism:

step 1) NO2 + NO2  NO + NO3                            (slow)
step 2) NO3 + CO  NO2 + CO2                            (fast)

What is the overall order of the chemical reaction being studied?

a)   0
b)   1
c)   2
d)   3
e)   4

Dr. Miller                                                                                     11
Practice Exam II
Chem 114
Spring 04
____39) Use the following chemical reaction and data to answer the following question.

2 NO (g) + O2 (g)  2 NO2 (g)

Experiment                [NO] M                   [O2] M             Initial Rate M/s
1                      0.0126                  0.0125                1.41 x 10-2
2                      0.0252                  0.0250                1.13 x 10-1
3                      0.0252                  0.0125                5.64 x 10-2

What is the value of the rate constant for this reaction in terms of the units given in the
data?

a)   89.5
b)   7110
c)   7160
d)   4.44 x 107

____40) Which of the following reactions will have the greatest rate at 298 K? Assume
that the frequency factor A is the same for all reactions.
a) E = +10 kJ/mol Ea = 25 kJ/mol
b) E = -10 kJ/mol Ea = 25 kJ/mol
c) E = +10 kJ/mol Ea = 11 kJ/mol
d) E = -10 kJ/mol Ea = 50 kJ/mol
e) E = +25 kJ/mol Ea = 25 kJ/mol

____41) The rate of formation of oxygen in the reaction
2N2O5(g)  4NO2(g) + O2(g)
is 2.28 (mol O2)L1s1. What is the rate of formation of NO2?
a)    0.57 (mol NO2)L1s1
b)    9.12 (mol NO2)L1s1
c)    2.28 (mol NO2)L1s1
d)    1.14 (mol NO2)L1s1
e)    4.56 (mol NO2)L1s1

____42) Given:
2NO2(g) + F2(g)  2NO2F(g)                        rate = [F2]/t
The rate of the reaction can also be expressed as
a)    2[NO2]/t.
b)    [NO2F]/t.
c)    ½[NO2]/t.
d)    [NO2]/t.
e)    ½[NO2F]/t.
Dr. Miller                                                                                    12
Practice Exam II
Chem 114
Spring 04
____43) The concentrationtime dependence for a first-order reaction is given below.

At which point on the curve is the reaction fastest?
a) A
b) B
c) C
d) A + t½
e) The rates are the same at all points.

____44) A first-order reaction has a rate constant of 0.00300 s1. The time required for
60% reaction is
a) 153 s.
b) 73.9 s.
c) 170 s.
d) 133 s.
e) 305 s.

____45) Technetium-99m, used to image the heart and brain, has a half-life of 6.00 h.
What fraction of technetium-99m remains in the body after 1 day?
a) 0.0625
b) 0.250
c) 0.0313
d) 0.125

Dr. Miller                                                                              13
Practice Exam II
Chem 114
Spring 04
____46) For the reaction             cyclopropane  propene
a plot of ln[cyclopropane] vs time in seconds gives a straight line with slope
4.1  103 s1 at 550C. What is the rate constant for this reaction?
a)    3.9  102 s1
b)    8.2  103 s1
c)    4.1  103 s1
d)    1.8  103 s1
e)    2.1  103 s1

____47) The rate law for the following mechanism is
NO2(g) + F2(g)  NO2F(g) + F(g)                         k1, slow
F(g) + NO2(g)  NO2F(g)                                 k2, fast
a)    rate = k2[NO2]2.
b)    rate = k2[NO2][F].
c)    rate = k1[NO2][F2].
d)    rate = k1k2[NO2]2.
e)    rate = k1[NO2F][F].

____48) A  particle corresponds to
a) 10e b) 10H+ c) 10e           d)   0
1n   e)   2
4He2+

____49) When an  particle is emitted, the mass number
a) decreases by 4.                          d) decreases by 1.
b) increases by 2.                          e) increases by 4.
c) decreases by 2.

____50) When radium-226, with Z = 88, undergoes  decay, the daughter nucleus is
a) thorium-230.                           d) polonium-222.
b) astatine-222.                          e) protactium-230.

____51) When 131I emits a  particle, what nuclide is produced?
a) 130I b) 127Sb c) 131Xe d) 131Te e) 130Te

____52) The nuclear equation for the disintegration of In-116 produces Sn-116 and
a) a positron. b) helium-4. c) a neutron. d) gamma rays. e) an electron.

____53) A nuclide undergoes  decay and forms 110I. What is the nuclide?
a) 112Cs    b) 114Cs c) 110Te d) 114I e) 110Xe

Dr. Miller                                                                             14
Practice Exam II
Chem 114
Spring 04
____54) Which of the following is most penetrating?
a)  b)        c) + d) 

____55) In the 238U decay series, there are eight  particles and six  particles lost
starting with  emission from 238U. What is the final product?
a) 207Pb     b) 210Po c) 210Bi         d) 208Pb e) 206Pb

____56) A 9.9-g sample of iodine-131 is stored for exactly 3 weeks. If the decay
constant is 0.0861 day1, what mass of the isotope remains?
a) 0.15 g b) 7.6 g c) 1.6 g d) 2.6 g e) 5.5 g

____57) The half-life of strontium-90 is 28.1 years. Calculate the percent of a strontium
sample left after 100 years.
a) 76% b) 0.34%            c) 63% d) 82% e) 8.5%

____58) Calculate the time required for the activity of a 9.0-mCi sodium-25 source to
decay to 7.0-mCi. The half-life of sodium-25 is 60.0 s.
a) 22 s    b) 44 s    c) 0.029 s     d) 19 s      e) 9.4 s

____59) The nuclear binding energy for lithium-7 is the energy released in the nuclear
reaction
a) 31H + 7n  7Li                            d) 31H + 4n  7Li
b) 6Li + n  7Li                              e) 71H  7Li
c) 31H + 4  7Li

____60) Which of the following nuclei is likely to capture an electron?
a) 9Li   b) 38Ca c) 246Am           d) 80Ge e) 24Mg

____61) Which of the following statements best describes what will happen when
magnesium metal is added to an aqueous solution containing 1.0 M ferric ion
(Fe3+) at 25 oC?

Mg2+ (aq) + 2 e-  Mg(s)                      Eo = -2.375 V
Fe3+ (aq) + 3 e-  Fe (s)                     Eo = -0.036 V

a) Mg (s) will be oxidized; Fe3+ (aq) will be reduced; the standard cell potential will
be 2.339 V.
b) Mg (s) will be oxidized; Fe3+ (aq) will be reduced; the standard cell potential will
be -2.339 V.
c) Fe3+ (aq) will be oxidized; Mg (s) will be reduced; the standard cell potential will
be -2.339 V.
d) Fe3+ (aq) will be oxidized; Mg (s) will be reduced; the standard cell potential will
be 2.339 V.
e) There is not enough information given to answer the question.

Dr. Miller                                                                               15
Practice Exam II
Chem 114
Spring 04
____62) Suppose you have been given the task of selecting a metal to be used as the
sacrificial anode for the cathodic protection of a buried iron fuel tank.
Considering the following standard reduction potentials,

Pd2+ (aq)   +   2 e-  Pd (s)                  Eo = 0.99 V
Ag+ (aq)    +   e-  Ag (s)                    Eo = 0.80 V
Cu2+ (aq)   +   2 e-  Cu (s)                  Eo = 0.34 V
Ni2+ (aq)   +   2 e-  Ni (s)                  Eo = -0.23 V
Fe2+ (aq)   +   2 e-  Fe (s)                  Eo = -0.41 V

Which of the following metals could be used as the sacrificial anode in this
application?

a) Pd            b) Ag          c) Cu          d) Ni          e) None of these

____63) When the equation:

MnO4- (aq) + Cl- (aq)  Mn2+ (aq) + Cl2 (aq)                   (acidic solution)

is balanced so that the coefficients have their smallest integer values, the
coefficient of H+ is:

a) 0             b) 2           c) 4           d) 8           e) 16

____64) Use the Standard Reduction Potentials given below to calculate Kf for
Zn(NH3)42+ shown being produced in the following reaction at 25 oC.

Zn2+ (aq) + 4 NH3 (aq)  Zn(NH3)42+ (aq)                              Kf = ??

Half-Reaction                                                         Eo , V

Zn(NH3)42+ (aq) + 2 e-  Zn (s) + 4 NH3 (aq)                          -1.04 V

Zn2+ (aq) + 2 e-  Zn (s)                                             -0.76 V

a) 1.5 x 10-61                                 d) 5.4 x 104
b) 3.5 x 10-10                                 e) 3.0 x 109
c) 1.9 x 10-5

Dr. Miller                                                                               16
Practice Exam II
Chem 114
Spring 04
____65) The cell potential for the electrochemical reaction shown below depends upon
the Cl- and Cu2+ concentrations. Calculate the cell potential (in V) at 25 oC if
[Cu2+] = 3.5 M and [Cl-] = 1.7 M. NOTE: the number of moles of electrons
transported in this reaction is equal to 2.

Cu2+ (aq) + 2 Cl- (aq) + 2Ag (s)  Cu (s) + 2 AgCl (s)                    Eo = 0.12 V

a)   0.15 V
b)   0.14 V
c)   0.12 V
d)   0.10 V
e)   0.090V

____66) Given the following table of standard reduction potentials:

Half Reaction                                    Eo (V)
I2 (s) + 2 e-  2 I- (aq)                               0.54
Cu2+ + 2 e-  Cu (s)                                   0.34
2 H+ (aq) + 2 e-  H2 (g)                                 0
Ni2+ (aq) + 2 e-  Ni (s)                               -0.28

The strongest oxidizing agent listed in the table is

a) I2          b) I-           c) Ni2+         d) Ni       e) H2

____67) A concentration cell is made up of the Fe/Fe2+ couple, where the Fe2+
concentrations are 1.0 M and 0.10 M. Which of the following statements best describes
the operation of this cell?

a) The anode compartment contains a 0.10 M Fe2+ solution which decreases in
concentration as the cell operates, and the cathode compartment contains a 1.0 M
Fe2+ solution which also decreases in concentration as the cell operates.
b) The anode compartment contains a 0.10 M Fe2+ solution which increases in
concentration as the cell operates, and the cathode compartment contains a 1.0 M
Fe2+ solution which decreases in concentration as the cell operates.
c) The anode compartment contains a 0.10 M Fe2+ solution which decreases in
concentration as the cell operates, and the cathode compartment contains a 1.0 M
Fe2+ solution which increases in concentration as the cell operates.
d) The anode compartment contains a 1.0 M Fe2+ solution which decreases in
concentration as the cell operates, and the cathode compartment contains a 0.10 M
Fe2+ solution which increases in concentration as the cell operates.
e) The anode compartment contains a 1.0 M Fe2+ solution which increases in
concentration as the cell operates, and the cathode compartment contains a 0.10 M
Fe2+ solution which decreases in concentration as the cell operates.

Dr. Miller                                                                           17
Practice Exam II
Chem 114
Spring 04
____68) What is the mass of chromium metal (expressed in grams) that is deposited
when a current of 15.0 A is passed through an aqueous solution of Cr(NO3)3 (the
half reaction is shown below) for 35.0 minutes?
Molar mass: Cr = 52.0 g/mol;

Cr3+ (aq) + 3 e-        Cr (s)

Answer                    Grams of Cr
a)                         0.10 g
b)                         0.28 g
c)                         5.66 g
d)                         17.0 g

____69) A nonspontaneous electrochemical reaction has:

a)   Go = 0;   Eo = 0;   K>1
b)   Go < 0;   Eo > 0;   K>1
c)   Go > 0;   Eo < 0;   K<1
d)   Go > 0;   Eo < 0;   K>1
e)   Go < 0;   Eo = 0;   K>1

The next three questions are based on the voltaic cell sketched below:

____70) The spontaneous reaction that takes place in this cell is:

a) Zn + Au  Zn2+ + Au +                      d) 2 K + Au +  2 K+ + Au
b) Zn + Au +  Zn2+ + Au                      e) Zn2+ + 2 K  2 K+ + Zn
d) Zn2+ + Au  Zn + Au +

Dr. Miller                                                                          18
Practice Exam II
Chem 114
Spring 04
____71) When the cell is operating:

a) e- flow through the external circuit to the Zn electrode while K+ diffuses into
the Zn/Zn2+ half cell and Cl- diffuses into the Au/Au + half cell.
b) e- flow through the external circuit to the Zn electrode while K+ diffuses into
the Au/Au + half cell and Cl- diffuses into the Zn/Zn2+ half cell.
c) e- flow through the external circuit to the Au electrode while K+ diffuses into
the Zn/Zn2+ half cell and Cl- diffuses into the Au/Au + half cell.
d) e- flow through the external circuit to the Au electrode while K+ diffuses into
the Au/Au + half cell and Cl- diffuses into the Zn/Zn2+ half cell.
e) e- flow through the external circuit to the Au electrode and through the salt
bridge to the Zn electrode.

____72) Pt electrodes are often used in voltaic cells. The above cell could continue to
operate if:

a)   both the Zn and Au electrodes were replaced by Pt electrodes.
b)   The Zn electrode were replaced by Pt; however, the Au electrode is needed.
c)   The Au electrode were replaced by Pt; however, the Zn electrode is needed.
d)   Either electrode is replaced by Pt and the other electrode remains as before.
e)   The cell cannot operate if there is a change in the electrodes.

____73) Given the following information;

Half Reaction                                         Eo red
2 H+ (aq) + 2 e-  H2 (g)                                   +0.00
Sn2+ (aq) + 2e-  Sn (s)                                    -0.136

Consider an electrochemical cell based on this reaction:

2 H+ (aq) + Sn(s)  Sn2+ (aq) + H2 (g)

Determine which of the following actions would increase the measured cell
potential.

a)   Increasing the pressure of the hydrogen gas in the hydrogen cell.
b)   Increasing the tin (II) ion concentration.
c)   Lowering the pH in the cathode compartment.
d)   Increasing the pH in the cathode compartment.
e)   Any of these things will increase the measured cell potential.

Dr. Miller                                                                                  19
Practice Exam II
Chem 114
Spring 04
____74) Which of the following reactions are oxidation-reduction reactions?

i) 2 Cu+ (aq)  Cu (s) + Cu2+
ii) 2 NO2 (g)  N2O4 (g)
iii) 2 H2 (g) + O2 (g)  2 H2O (g)
iv) NaCl (s)  Na+ (aq) + Cl- (aq)
v) CN- (aq) + HOCl (aq)  HCN (aq) + OCl- (aq)

a) i & ii       b) i and iii    c) i, ii and iii      d) ii, iii and v

____75) When the following equation is completed and balanced:

Pb(OH)42- (aq) + ClO- (aq)  PbO2 (s) + Cl- (aq) (basic solution)

the coefficients of OH- and H2O, respectively, are:

a)   0 and 3
b)   2 and 3
c)   2 and 2
d)   1 and 1
e)   2 and 1

____76) In an electrochemical process called “electrolysis”, H2 gas and O2 gas can be
obtained by passing an electric current through liquid water,

2 H2O (l)  2 H2 (g) + O2 (g)

Which species is the OXIDIZING AGENT and which species is the
REDUCING AGENT in this reaction, respectively?

a)   H2O (l); H2 (g)
b)   O2 (g); H2O (l)
c)   H2O (l); H2O (l)
d)   O2 (g); H2 (g)
e)   H2 (g); H2O (l)

Dr. Miller                                                                              20
Practice Exam II
Chem 114
Spring 04
Use the following equation, which occurs spontaneously at 25 oC, and Eo cell voltage
for questions 17 - 22.

2 Al (s) + 3 Fe2+ (aq)  2 Al3+ (aq) + 3 Fe                 Eo cell = 1.22 V

____77) Which of the following correctly describes the two half cells making up this
cell?

a) Anode:      Al foil in a solution of Al(NO3)3
Cathode:    Al foil in a solution of Fe(NO3)2
b) Anode:      Pt foil in a solution of Al(NO3)3
Cathode:    Pt foil in a solution of Fe(NO3)2
c) Anode:      Al foil in a solution of Al(NO3)3
Cathode:    Fe foil in a solution of Fe(NO3)2
d) Anode:      Fe foil in a solution of Al(NO3)3
Cathode:    Al foil in a solution of Fe(NO3)2
e) Anode:      Al foil in a solution of Fe(NO3)2
Cathode:    Fe foil in a solution of Al(NO3)3

____78) Which of the following correctly describes the flow of electrons in a cell made
up of Al and Fe electrodes?

a)   Electrons flow from the Al anode (+ terminal) to the Fe cathode (- terminal).
b)   Electrons flow from the Al anode (- terminal) to the Fe cathode (+ terminal).
c)   Electrons flow from the Fe cathode (- terminal) to the Al anode (+ terminal).
d)   Electrons flow from the Fe anode (- terminal) to the Al cathode (+ terminal).
e)   Electrons flow from the Fe anode (+ terminal) to the Al cathode (- terminal).

____79) The Fe and Al half-cells are connected by a KCl solution salt bridge. Which of
the following correctly describes the operation of the salt bridge?

a) K+ ions migrate into the Al half cell to make up for the decrease in Al3+ ions;
K+ ions also migrate into the Fe half cell to make up for the decrease in Fe2+
ions.
b) K+ ions migrate into the Al half cell to make up for the decrease in Al3+ ions;
Cl- ions migrate into the Fe half cell to balance the increase in Fe2+ ions.
c) K+ and Cl- ions migrate into both half cells in order to maintain the neutrality
of the solutions in both half cells.
d) K+ ions migrate into the Fe half cell to make up for the decrease in Al3+ ions;
Cl- ions migrate into the Al half cell to balance the increase in Fe2+ ions.
e) K+ ions migrate into the Fe half cell to make up for the decrease in Fe2+ ions;
Cl- ions migrate into the Al half cell to balance the increase in Al3+ ions.

Dr. Miller                                                                                21
Practice Exam II
Chem 114
Spring 04
____80) The standard reduction potential of the Al3+ + 3 e-  Al half reaction is
-1.66 V. Calculate the standard reduction potential (in volts) of the
Fe2+ + 2 e-  Fe half reaction.

a)   + 1.66 V
b)   +0.44 V
c)   0.00 V
d)   –0.44 V
e)   –1.66 V

____81) Calculate the value for E (in volts) for the above cell at 25 oC when the
concentration of Fe2+ is 0.15 M and that for Al3+ is 1.65 M?

a)   1.22 V
b)   1.21 V
c)   1.20 V
d)   1.19 V
e)   1.18 V

____82) Given the following electrochemical reaction:

Pb (s) + 2 Ag+ (aq)  Pb2+ (aq) + 2 Ag (s)                   Eocell = 0.93 V

Calculate K and Go at 25 oC.

K                       Go (kJ/mole)
a)                         5.1 x 1015                      89.7
b)                         2.6 x 1031                      89.7
c)                         5.1 x 1015                      -180
d)                         2.9 x 1031                      -180
e)                         2.6 x 1031                     - 89.7

Dr. Miller                                                                            22
Practice Exam II
Chem 114
Spring 04
____83) A concentration cell involving the reaction:

Fe (s)  Fe2+ (aq) + 2 e-

uses a 0.100 M solution of Fe2+ in the anode half cell and a 1.00 M solution of
Fe2+ in the cathode half cell. What is the cell potential of this concentration cell
expressed in volts? The standard reduction potential for the Fe/Fe2+ half reaction
Fe2+ (aq) + 2 e-  Fe (s) is –0.44 V.

a)   -0.0592 V
b)   -0.0296 V
c)    0.0000 V
d)   +0.0296 V
e)   +0.0592 V

____84) Given the following table of standard reduction potentials:

Cu2+ + 2 e-  Cu                       Eo = +0.34 V
2 H+ + 2 e-  H2 (g)                   Eo = 0.0 V
Zn2+ + 2 e-  Zn                       Eo = - 0.76 V

the strongest reducing agent listed in the table is:

a)   Zn2+
b)   H+
c)   Cu2+
d)   Cu
e)   Zn

____85) How many hours would it take to apply a chromium plating of thickness
2.00 x 10-2 mm to a car bumper of surface area 0.250 m2 in an electrolysis cell
carrying a current of 75.0 A? [The density of chromium is 7.19 g/cm3.]
Chromium plating occurs using electrolysis of objects suspended in a
dichromate solution, which follows this half reaction;

Cr2O72- (aq) + 12 e- + 14 H+ (aq)  2 Cr (s) + 7 H2O (l)

a) 2.22 h       b) 1.48 h      c) 3.05 h       d) 0.250 h      e) 2.56 h

Dr. Miller                                                                                23
Practice Exam II
Chem 114
Spring 04
____86) Iron can be protected against corrosion by cathodic protection. In this process:

a)   A metal that is a stronger reducing agent than iron serves as the cathode.
b)   A metal that is a strong oxidizing agent than iron serves as the cathode.
c)   A metal that is a weaker reducing agent than iron serves as the anode.
d)   A metal that is a stronger oxidizing agent than iron serves as the anode.
e)   A metal that is a stronger reducing agent than iron serves as the anode.

Dr. Miller                                                                             24
Practice Exam II
Chem 114
Spring 04
Practice Exam 1b Chemistry 114
Spring 2002
Dr. Miller
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Dr. Miller                                           25
Practice Exam II
Chem 114
Spring 04
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Dr. Miller                   26
Practice Exam II
Chem 114
Spring 04

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