Chemistry 116: General Chemistry
Syracuse University Project Advance
Exam #3, Spring 2007
Name
Date
The last page of the examination are reference tables.
[Gas constant = 0.00831 kJ/mol K; 1 faraday = 96.5 kJ/V mol e-]
1) What is the thermodynamic quantity that provides the criterion for the spontaneity of a
chemical reaction?
a) S
b) TS
c) U
d) H
e) G
2) The total entropy of a system and its surroundings always increases for a spontaneous process.
This is a statement of
a)
b)
c)
d)
e)
the first law of thermodynamics.
the law of constant composition.
the second law of thermodynamics.
the law of conservation of matter.
the third law of thermodynamics.
3) Which of the following has the LOWEST value of the absolute entropy per mole?
a)
b)
c)
d)
e)
gaseous sodium at 900°C and 1 atm
gaseous sodium at 900°C and 0.5 atm
liquid sodium at 100°C
solid sodium at 30°C
a solid solution of sodium in potassium at 30°C
4) Which of the following processes would be expected to have a positive S value?
a)
b)
c)
d)
e)
I2(g) 
 I2(s)
2NO(g) + O2(g) 
 2NO2(g)
2ClBr(g) 
 Cl2(g) + Br2(g)
NH4HS(s) 
 NH3(g) + H2S(g)
2H2(g) + O2(g) 
 2H2O(g)
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Spring 2007 Exam #3
5) For the reaction below H = 131.3 kJ and S = 133.6 J/K. Assuming H and S do not
vary with temperature, at what temperature will this reaction become spontaneous?
C(s) + H2O(g)  CO(g) + H2(g)
a) 273oC
b) 325oC
c) 552oC
d) 710oC
e) none of these
6) Using the thermodynamic data at 25oC, determine the value of Ho (in kJ) for the reaction.
C2H2(g) + 2H2(g)  C2H6(g)
Substance
C2H2(g)
C2H4(g)
C2H6(g)
H2(g)
H2O(g)
C2H5OH(l)
DGof (kJ/mole)
209
68
-33
0
-229
-175
So (J/mole)
201
219
230
131
189
161
a) -173
b) 236
c) -311
d) -248
e) none of these
7) Calculate S for the decomposition of ozone to oxygen.
2O3(g) 
 3O2(g)
S° = 205 J/(mol • K) for O2(g) and 239 J/(mol • K) for O3(g) at 25°C.
a)
b)
c)
d)
e)
+137 J/(mol • K)
–137 J/(mol • K)
+34 J/(mol • K)
–34 J/(mol • K)
+444 J/(mol • K)
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Spring 2007 Exam #3
8) For a reaction that has an equilibrium constant of 3  102, which of the following statements
must be true?
H is positive.
G is positive.
S is positive.
H is negative.
G is negative.
a)
b)
c)
d)
e)
9) Consider the following reaction at 25oC.
Go = 91.2 kJ , Ho = 131.4 kJ
C(s) + H2O(l)  CO(g) + H2(g)
What is the value of So (in J/K) for this reaction at 25oC?
a) -135
b) 1.6
c) -1.6
d) 135
e) 40
10) Condensation is a process for which
a) H and S are negative
b) H and S are positive
c) G is positive at all temperatures
d)G is negative at high temperature but positive at low temperature
e) the signs of H and S depend on the substance
11) Which of the following has a non-zero free energy of formation?
a)
b)
c)
d)
e)
N2(g)
S8(s)
Fe(l)
Br2(l)
Hg(l)
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12) The following reaction has G˚ = 42.6 kJ/mol at 25˚C. What is Ka for the acid HB?
HB(aq) + H2O(l)
a)
b)
c)
d)
e)
B-(aq) + H3O+(aq)
-17.2
3.41  10-8
1.13  10-5
1.63
14.0
13) Consider the following reactions I and II:
I.
II.
3Fe(s) + 2O2(g)   Fe3O4(s)
C(graphite) + O2(g)   CO2(g)
Go = -1014.2 kJ
Go = -394.4 kJ
What is the change in free energy, G, (in kJ) for reaction III shown below?
III.
Fe3O4(s) + 2C(graphite)   3Fe(s) + 2CO2(g)
a) +1802.4
b) +619.8
c) +225.4
d) +788.2
e) -788.2
14) An oxidation-reduction reaction is one that involves at least one change of
a)
b)
c)
d)
e)
formal charge.
oxidation potential.
oxidation state.
atomic number.
polarity.
15) How many electrons are involved in the following reaction?
Cl2 + 2Br-  2Cl- + Br2
a) 6
b) 2
c) 1
d) 4
e) 3
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16) When the basic solution redox equation, MnO4- + CN- MnO2 + CNO-, is properly
balanced, the coefficients of the reactants and products shown are, in order,
a) 1, 1, 1, 1
b)1, 2, 1, 2
c)2, 1, 2, 1
d)1, 3, 1, 3
e)2, 3, 2, 3
17) Given the standard potential for the reaction of hydrogen and oxygen,
2H2 + O2  2H2O
E˚ = +1.23 V
what is the standard potential for the following reaction?
H2O  H2 + (1/2)O2
a)
b)
c)
d)
e)
-2.46 V
-1.23 V
-0.625 V
0.625 V
1.23 V
18) A two-compartment electrochemical cell has a silver electrode immersed in 1.0 M AgNO3 in
one compartment, and a zinc electrode immersed in 1.0 M Zn(NO3)2 in the other. A salt
bridge connects the two compartments, and the electrodes are connected through a voltmeter.
The standard reduction potentials are
Ag+ + e-  Ag
Zn2+ + 2e-  Zn
E˚ = +0.80 V
E˚ = -0.76 V
Which of the following statements is false?
a)
b)
c)
d)
e)
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The silver electrode is the cathode.
The standard cell potential for this cell is 1.56 V.
The zinc electrode will lose mass, and the silver electrode will gain mass.
Electrons in the external circuit will flow from zinc to silver.
Increasing [Zn2+] will increase the cell voltage.
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Spring 2007 Exam #3
19) Of the following, which is the strongest reducing agent?
a) Li
b) Zn2+
c) Au
d)Cs+
e)Hg
20) Which of the following statements, referring to the reaction below, is correct?
N2(g) + 3Cl3(g)  2NCl3(g)
a) The N2 is an oxidizing agent and the Cl2 is a reducing agent.
b) The Cl2 is an oxidizing agent and the N2 is a reducing agent.
c) Both N2 and Cl2 are oxidizing agents.
d) Both N2 and Cl2 are reducing agents.
e) No oxidation or reduction occurs in this reaction.
21) For a galvanic cell with a cell potential of 1.5 V and a transfer of two electrons in the
balanced chemical equation, what is the equilibrium constant at 25˚C for the net spontaneous
cell reaction?
a)
b)
c)
d)
e)
3.7  10-6
1.1  10-3
130
2.4  1025
5.6  1050
22) What is the voltage (in volts) of the following cell at 25oC?
Cu(s) | Cu+2 (1.0 M) || Ag+ (1.0 x 10-3 M) | Ag(s)
a) 0.11
b) 0.28
c) 0.37
d) 0.55
e) none of these
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EC) For the reaction: AgBr(s)   Ag+(aq) + Br-(aq). The Ksp is 7.7 x 10-13 at 25oC.
Determine G for the reaction when [Ag+] = 1.0 x 10-2 and [Br-] = 1.0 x 10-3 M.
SHOW ALL WORK.
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