CHEMISTRY 112 Homework Test 2
Jun. 8, 2012
FORM A
--------------------------------------------------------------------------------------------------------------1.
Which of the following statements is correct when solid NH4Cl is added to a solution
of NH3?
A.
The concentration of NH4+ increases and those of NH3 and H+ decrease.
B.
The concentrations of both NH4+ and NH3 increase but that of H+ decreases.
+
+
C.
The concentrations of both NH4 and H increase but that of NH3 decreases.
D.
The concentrations of NH4+, NH3, and H+ all increase.
E.
None of the above statements is correct.
--------------------------------------------------------------------------------------------------------------2.
Which compound below has chlorine in the highest oxidation state?
--------------------------------------------------------------------------------------------------------------4.
Which one of the following oxides is acidic?
A.
B.
C.
D.
E.
KO2
CO2
CaO
Al2O3
Na2O
--------------------------------------------------------------------------------------------------------------5.
The solubility of PbCl2 is 1.6 ! 10–2 mol/L. What is the Ksp of PbCl2?
A.
5.0 ! 10–4
B.
4.1 ! 10–6
C.
3.1 ! 10–7
D.
1.6 ! 10–5
E.
2.6 ! 10–4
A.
HCl
B
Cl2
C.
HClO3
D
ICl3
A.
2SO2(g) + O2(g) " 2SO3(g)
ClF3
B.
NH4Cl(s) " NH3(g) + HCl(g)
C.
PbCl2(s) " Pb2+(aq) + 2Cl (aq)
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D.
2C(s) + O2(g) " 2CO2(g)
3.
E.
H2O(!) " H2O(g)
E
If Na reacts with element X to form an ionic compound with the formula Na3X, then
Ca will react with X to form:
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!S is negative for the reaction __________.
"
--------------------------------------------------------------------------------------------------------------7.
Which substance is serving as the reducing agent in the following reaction?
A.
CaX2
B.
CaX
C.
Ca2X3
A.
HNO3
D.
Ca3X2
B.
Fe2S3
E.
Ca2X
C.
NO2
D.
S
E.
H2 O
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Fe2S3(s) + 12HNO3(aq) # 2Fe(NO3)3(aq) + 3S(s) + 6NO2(g) + 6H2O(!)
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-----------------------------------------------------------------------------------------------------------Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
Substance
!H°f (kJ/mol)
C2H2(g)
226.7
S (J/K-mol)
209.2
200.8
C2H4(g)
52.30
68.11
219.4
C2H4(g)
"84.68
"32.89
229.5
2IO3–(aq) + 10e– + 12H+(aq)
A.
It will increase.
B.
It will decrease.
I2(s) + 6H2O(!)
CO (g)
"110.5
"137.2
197.9
CO2(g)
"393.5
"394.4
213.6
C.
It will not change.
205.0
D.
There is not enough information to determine this.
O2(g)
H2O(!)
8.
!G°f (kJ/mol)
-----------------------------------------------------------------------------------------------------------10.
Consider the half reaction below. What will happen to the E of this half cell if the
iodate concentration [IO3–] is increased?
0
0
"285.83
"237.13
69.91
----------------------------------------------------------------------The combustion of acetylene in the presence of excess oxygen yields carbon dioxide
and water:
2 C2H2(g) + 5O2(g) " 4CO2(g) + 2H2O(!)
What is the value of !S° for this reaction?
--------------------------------------------------------------------------------------------------------------11. The standard cell potential (E°cell) for the reaction below is +2.20 V. What is !G°?
2 Al(s) + 3 I2 (s) " 2 Al3+ (aq) + 6 I–(aq)
A.
+637 kJ
B.
"424 kJ
"637 kJ
A.
+689.3 J/K
C.
B.
+122.3 J/K
D.
"1060 kJ
C.
+432.4 J/K
E.
"1274 kJ
D.
"122.3 J/K
E.
"432.4 J/K
--------------------------------------------------------------------------------------------------------------9.
Calculate E° for a cell in which the overall reaction is
Pb(s) + 2Ag+(aq) # Pb2+(aq) + 2Ag(s)
A.
0.67 V
B.
0.93 V
C.
1.73 V
D.
1.47 V
E.
1.06 V
E° = 1.195 V
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--------------------------------------------------------------------------------------------------------------12.
Which of the following solutions could produce a buffer?
A.
B.
C.
D.
E.
a mixture of NaOH and HCl
a mixture of HCl and HClO4
a mixture of NaOH and NaCl
a mixture of HCl and NaF
a mixture of HCl and NaClO4
-----------------------------------------------------------------------------------------------------------13.
100 ml of 0.100 M HCl is titrated with 0.100 M NaOH. What is the pH when the
titration is half way to the equivalence point?
A.
B.
C.
D.
E.
1.48
3.50
4.63
7.00
8.30
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--------------------------------------------------------------------------------------------------------------14.
What is the coefficient of Fe3+ when the following equation is balanced?
CN–(aq) + Fe3+(aq) " CNO–(aq) + Fe2+(aq)
(basic solution)
--------------------------------------------------------------------------------------------------------------17.
Dissolving ammonium chloride (NH4Cl) in water lowers the temperature of the
water. For this dissolving process:
A.
1
A.
!H is negative and !S is negative
B.
2
B.
!H is positive and !S is positive
C.
3
C.
!H is negative and !S is positive
D.
4
D.
!H is positive and !S is negative
E.
5
E.
!G is positive at high T
--------------------------------------------------------------------------------------------------------------15.
Which of the following will be more soluble in acid solution than in pure water?
--------------------------------------------------------------------------------------------------------------18.
Coupled reactions are extremely important in living systems. For example, $G° is
given for 2 reactions
i.
Na3PO4
ii.
AlCl3
1. A + B " C + D
$G° = + 50 kJ.
iii.
KCl
2. C + E " X + Y
$G° = " 60 kJ.
What is $G° for the sum of reactions 1 and 2?
A.
i
B.
ii
C.
iii
D.
i and ii
E.
ii and iii
A + B + E " D + X + Y $G° = ???
--------------------------------------------------------------------------------------------------------------16.
Calculate the solubility of aluminum hydroxide, Ksp = 1.9 ! 10–33, in 0.0182 M
KOH solution.
A.
A.
"10 kJ
B.
110 kJ
C.
"110 kJ
D.
"3000 kJ
E.
50 kJ
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3.2 ! 10–28 M
B.
2.9 ! 10 M
C.
1.2 ! 10–11 M
Consider the titration of 50.0 mL of 0.217 M HN3 (Ka = 2.6 ! 10–5) with 0.183 M
NaOH. Calculate the pH of the solution after the addition of 29.7 mL of NaOH
solution.
D.
3.1 ! 10–12 M
A.
2.61
B.
8.79
C.
12.21
D.
7.00
E.
4.59
E.
19.
–9
–17
4.4 ! 10
M
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Given that for carbonic acid, H2CO3, Ka1 = 4.3 ! 10–7 and Ka2 = 5.6 ! 10–11, calculate
the pH of a solution formed by mixing 50 ml of 0.20 M NaHCO3 and 50 ml of 0.20
M Na2CO3.
A.
3.75
B.
6.37
C.
7.00
D.
7.63
E.
10.25
--------------------------------------------------------------------------------------------------------------22.
AgCl is a sparingly soluble salt with Ksp = 1.8 ! 10"10 . If AgCl is added to 0.01M
KCN(aq), what is the equilibrium constant for the process that will occur? (Kf of
Ag(CN)2" = 1.0 ! 1021.
AgCl(s) + 2KCN(aq)
Ag(CN)2"(aq) + 2K+(aq) + Cl" (aq)
A.
B.
C.
D.
E.
1.8 ! 10"10
5.6 ! 10"12
1.0 ! 1021
5.6 ! 1030
1.8 ! 1011
--------------------------------------------------------------------------------------------------------------21.
Calculate the [Cr+3] in equilibrium with Cr(OH)4"(aq) when 0.010 mol of Cr(NO3)3 is
dissolved in a liter of solution buffered at a pH of 7.3. Kf for Cr(OH)4"(aq) is 8.0 ! 1029.
"3
--------------------------------------------------------------------------------------------------------------23.
If there is a vessel which contains at least some amount of the reactants and
products, and the reaction below has !G° = +512 kJ, what can be said about the
equilibrium mixture?
A.
1.98 ! 10 M
B.
2.00 ! 10"7 M
C.
7.88 ! 10"6 M
D.
3.05 ! 10"8 M
A.
It will consist almost exclusively of A and D.
E.
1.60 ! 1023 M
B.
It will consist almost exclusively of A and Z.
C.
It will consist almost exclusively of X and Z.
D.
It will consist of significant amounts of A, D, X, and Z.
E.
It has a composition predictable only if one knows T and !H°.
-------------------------------------------------
A (!) + 2D (g)
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3X (g) + Z (s):
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--------------------------------------------------------------------------------------------------------------24.
Given the thermodynamic data in the table below, calculate the equilibrium constant
at 25°C for the reaction:
2 SO2(g) + O2(g)
Substance
SO2(g)
O2(g)
SO3(g)
$H°f (kJ/mol)
"297
0
"395
A.
3.82 ! 1023
B.
1.06
C.
1.95
D.
2.32 # 1024
E.
More data are needed.
2SO3(g)
S°(J/mol-K)
249
205
256
--------------------------------------------------------------------------------------------------------------25.
!G° for the following reaction is –159.4 kJ at 25 °C.
N2H4 (g)
N2 (g) + 2H2 (g)
If you have a 1-liter tank at 25 °C in which the concentration of N2H4 (g) is 6.0 M,
[N2] = 1.3 # 10–3 M and [H2] = 2 # 10–4 M, what is the maximum amount of useful
work that could be obtained from this mixture?
A.
159.4 kJ
B.
95.7 kJ
C.
222.5 kJ
D.
63.7 kJ
E.
42.0 kJ
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END OF HOMEWORK TEST
Answer Key
1.
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3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
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20.
21.
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24.
25.
D
C
D
B
D
A
B
E
B
A
E
D
A
B
D
A
B
A
E
E
C
E
A
D
C