Chemistry 116: General Chemistry
Syracuse University Project Advance
Exam #3, Spring 2006
Name
Date
The last pages of this examination are reference tables.
[Gas constant = 0.008314 kJ/mol K; 1 faraday = 96500 coul/ mol e- ]
1) If H = -150 kJ/mol for a given process, then it
A.
B.
C.
D.
E.
needs a catalyst
does not need a catalyst
occurs slowly
is endothermic
is exothermic
2) For a spontaneous process, which one of the following is always positive?
A. G
B. H
C. Eo
D. S
E. None of these
3) For the reaction CH4(g) + N2(g) + 164 kJ 
 HCN(g) + NH3(g) at 25°C and 1
atm pressure, G  159kJ. Calculate S at 25°C.
A.
B.
C.
D.
E.
0.2 J/K
200 J/K
0.01677 J/K
16.77 J/K
None of these
4) Which of the following processes has the largest positive value for S˚?
A.
B.
C.
D.
E.
Ba(OH)2(s) + CO2(g)  BaCO3(s) + H2O(l)
N2(g) + H2(g)  2NH3(g)
2SO3(g)  2SO2(g) + O2(g)
AgNO3(aq) + HCl(aq)  AgCl(s) + HNO3(aq)
2Hg(l) + O2(g)  2HgO(s)
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5) Given that G˚ = 91.7 kJ/mol for the reaction, Ag+(aq) + I-(aq)  AgI(s),
calculate the value of Ksp for AgI at 25˚C.
A.
B.
C.
D.
E.
1.6 x 10-29
8.3 x 10-17
4.5 x 10-14
9.1 x 10-9
6.6 x 10-7
6) If H for a process is -64 kJ/mol and S is -154 J/mol K, the process will be spontaneous
A.
B.
C.
D.
E.
above 416 K
below 416 K
above 3570 K
at all temperatures
at no temperatures
7) Which of the following is true when one mole of CO2(g) changes to dry ice?
1. The entropy decreases.
2. The entropy increases.
3. The enthalpy decreases.
4. The enthalpy increases.
A.
B.
C.
D.
E.
1 only
2 only
1 and 4 only
2 and 3 only
1 and 3 only
8) Calculate the Go for the following reaction at 500 K.
Cu (s) + H2O (g)  CuS (s) + H2 (g)
Hof (kJ/mole)
0
-241.8
-155.2
0
Cu (s)
H2O (g)
CuO (s)
H2 (g)
A.
B.
C.
D.
E.
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So (J/K)
33.3
188.7
43.5
130.6
+110.6 kJ
-86.6 kJ
+23.9 kJ
-62.6 kJ
+301 kJ
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9) For the reaction: 3C (s) + 4H2 (g)  C3H8
So = -29 J/mole *K
Ho = -103.8 kJ/mole
Calculate the equilibrium constant at 25oC for the reaction above.
A.
B.
C.
D.
E.
1.04
0.962
2.09 x 10-17
4.79 x 1016
2.1 x 1032
10) Calculate the voltage of a cell in which the following reaction occurs:
Zn (s) + 2H+ (aq, 0.001 M)  Zn+2 (aq, 1M) + H2 (g, 1 atm)
Zn+2 + 2e-   Zn
The standard reduction potential for zinc is:
A.
B.
C.
D.
E.
Eo = -0.763 v
+0.73 v
+0.41 v
+0.58 v
+0.70 v
-0.41 v
11) Electrolysis refers to an electrochemical reaction that is
A.
B.
C.
D.
E.
exothermic.
spontaneous.
nonspontaneous, but forced to proceed.
voltaic.
oxidation-reduction.
12) What is the reducing agent in the following reaction?
PbO2(s) + Pb(s) + 4H+(aq) + 2SO42-(aq)  2PbSO4(s) + 2H2O(l)
A.
B.
C.
D.
E.
PbO2
Pb
H+
SO42PbSO4
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13) The flow of electrons through the external circuit attached to a voltaic cell is
A. from the anode to the cathode.
B. from the cathode to the anode.
C. only predictable once one knows what the half-reactions are.
14) Which of the following reactions is a redox reaction?
I.
K2CrO4 + BaCl2  BaCrO4 + 2KCl
II.
Pb22+ + 2Br-  PbBr
III.
Cu + S  CuS
A.
B.
C.
D.
E.
only I
only II
only III
I and II
all three (I, II and III)
15) Use the standard reduction potentials:
Cu2+  Cu+
+0.16 V
I2  I+0.54 V
Calculate the value of E° (in V) for a cell in which the overall reaction is
2Cu+ + I2  2Cu2+ + 2IA.
B.
C.
D.
E.
0.38 V
–0.38 V
0.68 V
–0.68V
0.83 V
16) Of the following, which is the strongest oxidizing agent?
A.
B.
C.
D.
E.
Ni2+
Li+
Fe2+
F2
Al
17) What process occurs at an anode?
A.
B.
C.
D.
oxidation
reduction
oxidation and/or reduction
neither oxidation nor reduction
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18) When the basic solution redox equation, BrO- + Fe(OH)2 Br- + Fe(OH)3, is
properly balanced, the coefficients of the reactants and products shown are, in order,
A.
B.
C.
D.
E.
1, 1, 1, 1
1, 2, 1, 2
2, 1, 2, 1
1, 3, 1, 3
2, 5, 2, 5
19) If a piece of tin and a piece of copper were submerged in a solution containing SnSO4 and
CuCl2, what would happen?
Cu+2(aq) + 2e-  Cu(s)
E° = 0.337 V
Sn+2(aq) + 2e-  Sn(s)
E° = -0.136 V
A.
B.
C.
D.
E.
The tin electrode would gain weight and the copper electrode lose weight.
The tin electrode would gain weight and the copper electrode gain weight.
The tin electrode would lose weight and the copper electrode lose weight.
The tin electrode would lose weight and the copper electrode gain weight.
Nothing would happen.
20) Which of the following is(are) true about an electrochemical reaction that is spontaneous in
its standard state?
A.
B.
C.
D.
E.
The standard electromotive force is positive.
The standard free energy decreases.
The entropy of the universe increases.
All of the above.
None of the above.
21) The two electrodes Cr(s)/Cr3+(aq) and Sn(s)/Sn2+(aq) are combined to afford a spontaneous
electrochemical reaction. The standard reduction potentials in V for Cr3+(aq) and Sn2+(aq)
are –0.74 and –0.14, respectively. E° in V for this cell is
A.
B.
C.
D.
E.
+0.88
–0.88
+0.60
–0.60
+2.50
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22) What is the half-reaction occurring at the cathode in the voltaic reaction below?
3MnO4-(aq) + 24H+(aq) + 5Fe(s) 3Mn2+(aq) + 5Fe3+(aq) + 12H2O(l)
A.
B.
C.
D.
E.
MnO4-(aq) + 8H+(aq) + 5e-  Mn2+(aq) + 4H2O(l)
2MnO4-(aq) + 12H+(aq) + 6e-  2Mn2+(aq) + 3H2O(l)
Fe(s)  Fe3+(aq) + 3eFe(s)  Fe2+(aq) + 2eFe2+(aq)  Fe3+(aq) + e-
23) Lithium is produced by the electrolysis of lithium chloride as follows:
2 LiCl (l)  2 Li (l) + Cl2 (g)
During passage of a certain current for 45 minutes, 169 grams of lithium were produced.
How many liters of Cl2 gas (measured at STP) were produced?
A.
B.
C.
D.
E.
(169)(22.4) / (70.9)
(45)(60)(169) / (2)(96500)
(169)(22.4) / (6.94)(2)
(45)(60)(22.4) / (96500)
(169)(70.9) / (6.94)
EXTRA CREDIT:
Consider the cell: Zn(s) | Zn+2 (0.10 M) || H+ (aq) | H2 (g) (1 atm)
This cell can be used to provide a measure of the pH in the cathode compartment. What
is the pH in the cathode compartment if the cell emf is measured to be 0.60 v when
[Zn+2]=0.10 M and P H2 = 1 atm? (recall pH = -log[H+] ) SHOW ALL WORK
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