CHEM 1332
SPRING 2003
THIRD EXAM – APRIL, 18th – Version 1
1.
Which of the following mixtures would be classified as a buffer solution?
(A)
(B)
(C)
(D)
(E)
50 mL of 0.100 M HCl and 50 mL of 0.100 M KCl
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 25 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 0.500 mL of 0.000100 M NaOH
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M HCl
2.
Calculate the pH of a solution that is 0.250 M NH3 and 0.200 M NH4Br. Kb of NH3 = 1.8 x 10-5.
(A)
4.6
3.
A buffer solution is made by mixing 40.0 mL of 0.150 M HCOOH and 20.0 mL of 0.150 M NaHCOO. 10.0 mL of 0.0500 M
NaOH is then added to the solution. What is the pH of the final solution? Ka of HCOOH = 1.8 x 10-4.
(A)
2.83 x 10-5
4.
Which of the following describes the pH at the equivalence point when a weak acid is titrated with a strong base?
(A)
(B)
(C)
(D)
(E)
The pH < 7
The pH > 7
The pH = 7
The pH cannot be determined without further information
The pH = pKa of the acid.
5.
20.0 mL of 0.25 M hydrofluoric acid (Ka = 6.8 x 10-4) is titrated with 0.150 M KOH. Calculate the pH after 15.0 mL of the
base have been added.
(A)
2.95
(B)
(B)
(B)
4.8
3.55
3.08
(C)
(C)
(C)
8.0
4.55
3.25
1
(D)
(D)
(D)
9.2
9.45
3.58
(E)
(E)
(E)
9.4
10.45
10.9
6.
Which of the following indicators would be a good choice to use in a titration of HNO3 with LiOH?
(A)
(C)
(E)
phenolphthalein (pH range 8-10)
bromothymol blue (pH range 6-7.5)
alizarin yellow (pH range 10-12)
7.
Given that the solubility of magnesium hydroxide is 3.15 x 10-2 g/L, calculate the Ksp of this salt.
(A)
(D)
9.92 x 10-4
5.82 x 10-7
8.
What is the solubility (in mol/L) of silver bromide in a solution that is 0.200 M CaBr2? Ksp of AgBr is 5.0 x 10-13.
(A)
(D)
1.00 x 10-13
7.07 x 10-7
9.
A solution is 2.00 x 10-3 M Ba(NO3)2 and 0.0500 M KF. Given that the Ksp of barium fluoride is 1.5 x 10-6,
(A)
(C)
(E)
Qsp = 1 x 10-4 so a precipitate will be observed.
Qsp = 1 x 10-6 so no precipitate will be observed.
Qsp = 5 x 10-6 so a precipitate will be observed.
10.
Which of the following statements is FALSE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature of a system increases the entropy.
2 moles of a gas at one atmosphere pressure has a greater entropy than 2 moles of the same gas at 1000 mmHg pressure.
The reaction of O3(g) to produce O2(g) has a negative entropy change.
The Sº of methane (CH4) is less than that of ethane (C2H6).
A substance can only have zero entropy at absolute zero in a perfect crystal.
(D)
(B)
(E)
(B)
(E)
(B)
crystal violet (pH range 0-2)
methyl red (pH range 4.2-6.2)
1.25 x 10-4
6.3 x 10-10
(C)
1.25 x 10-12
5.00 x 10-5
(C)
(B)
(D)
2
2.92 x 10-7
1.25 x 10-11
Qsp = 2 x 10-4 so a precipitate will be observed.
Qsp = 2 x 10-5 so a precipitate will be observed.
11.
Consider the slightly soluble salt, barium carbonate, for which the ΔHsolution is exothermic. Which of the following statements
is TRUE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature will increase the solubility of barium carbonate in pure water.
Barium carbonate will be less soluble in acidic solution than in pure water.
Barium carbonate will be more soluble in a solution of sodium carbonate than in pure water.
Changing the pH will have no effect on the solubility of barium carbonate.
Barium carbonate will be less soluble in a solution of barium nitrate than in pure water.
12.
Calculate ΔSº for the reaction, 4 NH3(g) + 7 O2(g) → 4 NO2(g) + 6 H2O(g) given the following values of Sº in J/mol K:
Sº(NH3)
Sº(NO2)
=
=
193
240
Sº(O2)
Sº(H2O)
205
189
(A)
(D)
-113 J/K
+113 J/K
13.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
Vaporizing water has both positive ΔH and ΔS.
A process will be spontaneous if ΔSuniverse is positive.
Complex processes violate the laws of thermodynamics
ΔG for a given reaction cannot be measured directly.
A reaction can be endothermic but still be spontaneous.
14.
Calculate ΔGrxn for, 2 NOCl(g) → N2(g) + O2(g) + Cl2(g), given the following set of reactions:
(A)
(D)
(B)
(E)
=
=
-31 J/K
+1322 J/K
1/2 N2(g) + 1/2 O2(g) → NO
NO(g) + 1/2 Cl2(g) → NOCl
ΔG = 86.8 kJ
ΔG = -20.7 kJ
+66.1 kJ
-45.4 kJ
(B)
(E)
(C)
+152.9 kJ
-132.2 kJ
(C)
3
+31 J/K
+132.2 kJ
15.
Consider the reaction between CO(g) and Cl2(g) to form COCl2(g). At 298 K, ΔH = -220. kJ/mol and ΔG = -206 kJ/mol. At
what temperature will the reaction become non-spontaneous?
(A)
(D)
1.07 K
1070 K
16.
Calculate Keq at 150 ºC for the reaction, CH3OH(g) ' CO(g) + 2 H2(g), given that ΔHº = 90.9 kJ and ΔSº = 221 J/K,
(A)
0.480
17.
Once the oxidation-reduction reaction below is balanced in basic solution
(B)
(E)
(B)
2.08
15.7 K
4680 K
(C)
(C)
13.24
(D)
1070 ºC
2.36 x 1016
(E)
-37.7
–0.61 V
(E)
0.92 V
MnO4-(aq) + Br-(aq) ⎯→ MnO2(s) + BrO3-(aq)
(A)
(B)
(C)
(D)
(E)
The coefficient of hydroxide ions is 2, and it lies on the product side.
The coefficient of hydroxide ions is 2, and it lies on the reactant side.
The coefficient of water is 1, and it lies on the product side.
The coefficient of water is 2, and it lies on the reactant side.
None of the above.
18.
In basic solution, selenide and sulfite ions react spontaneously:
2 Se2-(aq) + 2 SO32-(aq) + 3 H2O(l) ⎯→ 2 Se(s) + 6 OH-(aq) + S2O32-(aq)
E°cell = 0.35V
If E°red (SO32-) is –0.57 V, what is E°red (Se)?
(A)
–0.22 V
(B)
+0.22 V
(C)
–0.92 V
4
D)
19.
What is the balanced equation for the cell notation:
Fe(s)⏐Fe2+(aq) NO3-(aq) ⏐NO(g) ⏐Pt(s)
(A)
(B)
(C)
(D)
(E)
Fe(s) + 2 H2O(l) + NO(g) ⎯→ Fe2+(aq) + NO3-(aq) + 4 H+(aq)
Fe2+(aq) + NO3-(aq) + 4 H+(aq) ⎯→ Fe(s) + 2 H2O(l) + NO(g)
3 Fe2+(aq) + NO(g) + 4 H2O(l) ⎯→ 3 Fe(s) + 8 H+(aq) + 2 NO3-(aq)
Fe(s) + NO3-(aq) + 4 H+(aq) ⎯→ NO(g) + Fe2+(aq) + 2 H2O(l)
3 Fe(s) + 2 NO3-(aq) + 8 H+(aq) ⎯→ 2 NO(g) + 3 Fe2+(aq) + 4 H2O(l)
20.
Consider the generalized voltaic cell shown below. Identify the following:
e-
e-
voltmeter
X
T
Z
S
Y
(i)
(ii)
(iii)
(iv)
electrode at which oxidation occurs
electrode that functions as the anode
electrode that gains mass as cell operates (assuming that a metal is produced)
the solution into which positive ions of the salt bridge will move to balance the charges
(A)
(B)
(C)
(D)
(E)
(i) X, (ii) X, (iii) T, (iv) S
(i) T, (ii) X, (iii) T, (iv) Y
(i) X, (ii) X, (iii) X, (iv) S
(i) T, (ii) T, (iii) X, (iv) S
(i) X, (ii) T, (iii)T, (iv) Y
5
CHEM 1332
SPRING 2003
THIRD EXAM – APRIL, 18th – Version 2
1.
Which of the following indicators would be a good choice to use in a titration of HNO3 with LiOH?
(A)
(C)
(E)
phenolphthalein (pH range 8-10)
bromothymol blue (pH range 6-7.5)
alizarin yellow (pH range 10-12)
2.
Given that the solubility of magnesium hydroxide is 3.15 x 10-2 g/L, calculate the Ksp of this salt.
(A)
(D)
9.92 x 10-4
5.82 x 10-7
3.
What is the solubility (in mol/L) of silver bromide in a solution that is 0.200 M CaBr2? Ksp of AgBr is 5.0 x 10-13.
(A)
(D)
1.00 x 10-13
7.07 x 10-7
4.
A solution is 2.00 x 10-3 M Ba(NO3)2 and 0.0500 M KF. Given that the Ksp of barium fluoride is 1.5 x 10-6,
(A)
(C)
(E)
Qsp = 1 x 10-4 so a precipitate will be observed.
Qsp = 1 x 10-6 so no precipitate will be observed.
Qsp = 5 x 10-6 so a precipitate will be observed.
5.
Which of the following statements is FALSE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature of a system increases the entropy.
2 moles of a gas at one atmosphere pressure has a greater entropy than 2 moles of the same gas at 1000 mmHg pressure.
The reaction of O3(g) to produce O2(g) has a negative entropy change.
The Sº of methane (CH4) is less than that of ethane (C2H6).
A substance can only have zero entropy at absolute zero in a perfect crystal.
(D)
(B)
(E)
(B)
(E)
(B)
crystal violet (pH range 0-2)
methyl red (pH range 4.2-6.2)
1.25 x 10-4
6.3 x 10-10
(C)
1.25 x 10-12
5.00 x 10-5
(C)
(B)
(D)
1
2.92 x 10-7
1.25 x 10-11
Qsp = 2 x 10-4 so a precipitate will be observed.
Qsp = 2 x 10-5 so a precipitate will be observed.
6.
Which of the following mixtures would be classified as a buffer solution?
(A)
(B)
(C)
(D)
(E)
50 mL of 0.100 M HCl and 50 mL of 0.100 M KCl
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 25 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 0.500 mL of 0.000100 M NaOH
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M HCl
7.
Calculate the pH of a solution that is 0.250 M NH3 and 0.200 M NH4Br. Kb of NH3 = 1.8 x 10-5.
(A)
4.6
8.
A buffer solution is made by mixing 40.0 mL of 0.150 M HCOOH and 20.0 mL of 0.150 M NaHCOO. 10.0 mL of 0.0500 M
NaOH is then added to the solution. What is the pH of the final solution? Ka of HCOOH = 1.8 x 10-4.
(A)
2.83 x 10-5
9.
Which of the following describes the pH at the equivalence point when a weak acid is titrated with a strong base?
(A)
(B)
(C)
(D)
(E)
The pH < 7
The pH > 7
The pH = 7
The pH cannot be determined without further information
The pH = pKa of the acid.
10.
20.0 mL of 0.25 M hydrofluoric acid (Ka = 6.8 x 10-4) is titrated with 0.150 M KOH. Calculate the pH after 15.0 mL of the
base have been added.
(A)
2.95
11.
Calculate Keq at 150 ºC for the reaction, CH3OH(g) ' CO(g) + 2 H2(g), given that ΔHº = 90.9 kJ and ΔSº = 221 J/K,
(A)
0.480
(B)
(B)
(B)
(B)
4.8
3.55
3.08
2.08
(C)
(C)
(C)
(C)
8.0
4.55
3.25
13.24
2
(D)
(D)
(D)
(D)
9.2
9.45
3.58
2.36 x 1016
(E)
(E)
(E)
(E)
9.4
10.45
10.9
-37.7
12.
Once the oxidation-reduction reaction below is balanced in basic solution
MnO4-(aq) + Br-(aq) ⎯→ MnO2(s) + BrO3-(aq)
(A)
(B)
(C)
(D)
(E)
The coefficient of hydroxide ions is 2, and it lies on the product side.
The coefficient of hydroxide ions is 2, and it lies on the reactant side.
The coefficient of water is 1, and it lies on the product side.
The coefficient of water is 2, and it lies on the reactant side.
None of the above.
13.
In basic solution, selenide and sulfite ions react spontaneously:
2 Se2-(aq) + 2 SO32-(aq) + 3 H2O(l) ⎯→ 2 Se(s) + 6 OH-(aq) + S2O32-(aq)
E°cell = 0.35V
If E°red (SO32-) is –0.57 V, what is E°red (Se)?
(A)
–0.22 V
(B)
+0.22 V
14.
What is the balanced equation for the cell notation:
(C)
–0.92 V
Fe(s)⏐Fe2+(aq) NO3-(aq) ⏐NO(g) ⏐Pt(s)
(A)
(B)
(C)
(D)
(E)
Fe(s) + 2 H2O(l) + NO(g) ⎯→ Fe2+(aq) + NO3-(aq) + 4 H+(aq)
Fe2+(aq) + NO3-(aq) + 4 H+(aq) ⎯→ Fe(s) + 2 H2O(l) + NO(g)
3 Fe2+(aq) + NO(g) + 4 H2O(l) ⎯→ 3 Fe(s) + 8 H+(aq) + 2 NO3-(aq)
Fe(s) + NO3-(aq) + 4 H+(aq) ⎯→ NO(g) + Fe2+(aq) + 2 H2O(l)
3 Fe(s) + 2 NO3-(aq) + 8 H+(aq) ⎯→ 2 NO(g) + 3 Fe2+(aq) + 4 H2O(l)
3
D)
–0.61 V
(E)
0.92 V
15.
Consider the generalized voltaic cell shown below. Identify the following:
e-
e-
voltmeter
X
T
Z
S
Y
(i)
(ii)
(iii)
(iv)
electrode at which oxidation occurs
electrode that functions as the anode
electrode that gains mass as cell operates (assuming that a metal is produced)
the solution into which positive ions of the salt bridge will move to balance the charges
(A)
(B)
(C)
(D)
(E)
(i) X, (ii) X, (iii) T, (iv) S
(i) T, (ii) X, (iii) T, (iv) Y
(i) X, (ii) X, (iii) X, (iv) S
(i) T, (ii) T, (iii) X, (iv) S
(i) X, (ii) T, (iii)T, (iv) Y
16.
Consider the slightly soluble salt, barium carbonate, for which the ΔHsolution is exothermic. Which of the following statements
is TRUE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature will increase the solubility of barium carbonate in pure water.
Barium carbonate will be less soluble in acidic solution than in pure water.
Barium carbonate will be more soluble in a solution of sodium carbonate than in pure water.
Changing the pH will have no effect on the solubility of barium carbonate.
Barium carbonate will be less soluble in a solution of barium nitrate than in pure water.
4
17.
Calculate ΔSº for the reaction, 4 NH3(g) + 7 O2(g) → 4 NO2(g) + 6 H2O(g) given the following values of Sº in J/mol K:
Sº(NH3)
Sº(NO2)
=
=
193
240
Sº(O2)
Sº(H2O)
(B)
(E)
=
=
205
189
(A)
(D)
-113 J/K
+113 J/K
-31 J/K
+1322 J/K
(C)
+31 J/K
18.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
Vaporizing water has both positive ΔH and ΔS.
A process will be spontaneous if ΔSuniverse is positive.
Complex processes violate the laws of thermodynamics
ΔG for a given reaction cannot be measured directly.
A reaction can be endothermic but still be spontaneous.
19.
Calculate ΔGrxn for, 2 NOCl(g) → N2(g) + O2(g) + Cl2(g), given the following set of reactions:
1/2 N2(g) + 1/2 O2(g) → NO
NO(g) + 1/2 Cl2(g) → NOCl
ΔG = 86.8 kJ
ΔG = -20.7 kJ
(A)
(D)
+66.1 kJ
-45.4 kJ
(B)
(E)
20.
Consider the reaction between CO(g) and Cl2(g) to form COCl2(g). At 298 K, ΔH = -220. kJ/mol and ΔG = -206 kJ/mol. At
what temperature will the reaction become non-spontaneous?
(A)
(D)
1.07 K
1070 K
(B)
(E)
+152.9 kJ
-132.2 kJ
(C)
15.7 K
4680 K
(C)
5
+132.2 kJ
1070 ºC
CHEM 1332
SPRING 2003
THIRD EXAM – APRIL, 18th – Version 3
1.
Consider the slightly soluble salt, barium carbonate, for which the ΔHsolution is exothermic. Which of the following statements
is TRUE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature will increase the solubility of barium carbonate in pure water.
Barium carbonate will be less soluble in acidic solution than in pure water.
Barium carbonate will be more soluble in a solution of sodium carbonate than in pure water.
Changing the pH will have no effect on the solubility of barium carbonate.
Barium carbonate will be less soluble in a solution of barium nitrate than in pure water.
2.
Calculate ΔSº for the reaction, 4 NH3(g) + 7 O2(g) → 4 NO2(g) + 6 H2O(g) given the following values of Sº in J/mol K:
Sº(NH3)
Sº(NO2)
=
=
193
240
Sº(O2)
Sº(H2O)
(B)
(E)
=
=
205
189
(A)
(D)
-113 J/K
+113 J/K
-31 J/K
+1322 J/K
3.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
Vaporizing water has both positive ΔH and ΔS.
A process will be spontaneous if ΔSuniverse is positive.
Complex processes violate the laws of thermodynamics
ΔG for a given reaction cannot be measured directly.
A reaction can be endothermic but still be spontaneous.
(C)
1
+31 J/K
4.
Calculate ΔGrxn for, 2 NOCl(g) → N2(g) + O2(g) + Cl2(g), given the following set of reactions:
1/2 N2(g) + 1/2 O2(g) → NO
NO(g) + 1/2 Cl2(g) → NOCl
ΔG = 86.8 kJ
ΔG = -20.7 kJ
(A)
(D)
+66.1 kJ
-45.4 kJ
(B)
(E)
5.
Consider the reaction between CO(g) and Cl2(g) to form COCl2(g). At 298 K, ΔH = -220. kJ/mol and ΔG = -206 kJ/mol. At
what temperature will the reaction become non-spontaneous?
(A)
(D)
1.07 K
1070 K
6.
Calculate Keq at 150 ºC for the reaction, CH3OH(g) ' CO(g) + 2 H2(g), given that ΔHº = 90.9 kJ and ΔSº = 221 J/K,
(A)
0.480
7.
Once the oxidation-reduction reaction below is balanced in basic solution
(B)
(E)
(B)
2.08
+152.9 kJ
-132.2 kJ
(C)
15.7 K
4680 K
(C)
(C)
13.24
(D)
+132.2 kJ
1070 ºC
2.36 x 1016
(E)
-37.7
(E)
0.92 V
MnO4-(aq) + Br-(aq) ⎯→ MnO2(s) + BrO3-(aq)
(A)
(B)
(C)
(D)
(E)
The coefficient of hydroxide ions is 2, and it lies on the product side.
The coefficient of hydroxide ions is 2, and it lies on the reactant side.
The coefficient of water is 1, and it lies on the product side.
The coefficient of water is 2, and it lies on the reactant side.
None of the above.
8.
In basic solution, selenide and sulfite ions react spontaneously. If E°red (SO32-) is –0.57 V, what is E°red (Se)?
2 Se2-(aq) + 2 SO32-(aq) + 3 H2O(l) ⎯→ 2 Se(s) + 6 OH-(aq) + S2O32-(aq)
(A)
–0.22 V
(B)
+0.22 V
(C)
–0.92 V
2
E°cell = 0.35V
D)
–0.61 V
9.
What is the balanced equation for the cell notation:
Fe(s)⏐Fe2+(aq) NO3-(aq) ⏐NO(g) ⏐Pt(s)
(A)
(B)
(C)
(D)
(E)
Fe(s) + 2 H2O(l) + NO(g) ⎯→ Fe2+(aq) + NO3-(aq) + 4 H+(aq)
Fe2+(aq) + NO3-(aq) + 4 H+(aq) ⎯→ Fe(s) + 2 H2O(l) + NO(g)
3 Fe2+(aq) + NO(g) + 4 H2O(l) ⎯→ 3 Fe(s) + 8 H+(aq) + 2 NO3-(aq)
Fe(s) + NO3-(aq) + 4 H+(aq) ⎯→ NO(g) + Fe2+(aq) + 2 H2O(l)
3 Fe(s) + 2 NO3-(aq) + 8 H+(aq) ⎯→ 2 NO(g) + 3 Fe2+(aq) + 4 H2O(l)
10.
Consider the generalized voltaic cell shown below. Identify the following:
e-
e-
voltmeter
X
T
Z
S
Y
(i)
(ii)
(iii)
(iv)
electrode at which oxidation occurs
electrode that functions as the anode
electrode that gains mass as cell operates (assuming that a metal is produced)
the solution into which positive ions of the salt bridge will move to balance the charges
(A)
(B)
(C)
(D)
(E)
(i) X, (ii) X, (iii) T, (iv) S
(i) T, (ii) X, (iii) T, (iv) Y
(i) X, (ii) X, (iii) X, (iv) S
(i) T, (ii) T, (iii) X, (iv) S
(i) X, (ii) T, (iii)T, (iv) Y
3
11.
Which of the following mixtures would be classified as a buffer solution?
(A)
(B)
(C)
(D)
(E)
50 mL of 0.100 M HCl and 50 mL of 0.100 M KCl
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 25 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 0.500 mL of 0.000100 M NaOH
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M HCl
12.
Calculate the pH of a solution that is 0.250 M NH3 and 0.200 M NH4Br. Kb of NH3 = 1.8 x 10-5.
(A)
4.6
13.
A buffer solution is made by mixing 40.0 mL of 0.150 M HCOOH and 20.0 mL of 0.150 M NaHCOO. 10.0 mL of 0.0500 M
NaOH is then added to the solution. What is the pH of the final solution? Ka of HCOOH = 1.8 x 10-4.
(A)
2.83 x 10-5
14.
Which of the following describes the pH at the equivalence point when a weak acid is titrated with a strong base?
(A)
(B)
(C)
(D)
(E)
The pH < 7
The pH > 7
The pH = 7
The pH cannot be determined without further information
The pH = pKa of the acid.
15.
20.0 mL of 0.25 M hydrofluoric acid (Ka = 6.8 x 10-4) is titrated with 0.150 M KOH. Calculate the pH after 15.0 mL of the
base have been added.
(A)
2.95
(B)
(B)
(B)
4.8
3.55
3.08
(C)
(C)
(C)
8.0
4.55
3.25
4
(D)
(D)
(D)
9.2
9.45
3.58
(E)
(E)
(E)
9.4
10.45
10.9
16.
Which of the following indicators would be a good choice to use in a titration of HNO3 with LiOH?
(A)
(C)
(E)
phenolphthalein (pH range 8-10)
bromothymol blue (pH range 6-7.5)
alizarin yellow (pH range 10-12)
17.
Given that the solubility of magnesium hydroxide is 3.15 x 10-2 g/L, calculate the Ksp of this salt.
(A)
(D)
9.92 x 10-4
5.82 x 10-7
18.
What is the solubility (in mol/L) of silver bromide in a solution that is 0.200 M CaBr2? Ksp of AgBr is 5.0 x 10-13.
(A)
(D)
1.00 x 10-13
7.07 x 10-7
19.
A solution is 2.00 x 10-3 M Ba(NO3)2 and 0.0500 M KF. Given that the Ksp of barium fluoride is 1.5 x 10-6,
(A)
(C)
(E)
Qsp = 1 x 10-4 so a precipitate will be observed.
Qsp = 1 x 10-6 so no precipitate will be observed.
Qsp = 5 x 10-6 so a precipitate will be observed.
20.
Which of the following statements is FALSE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature of a system increases the entropy.
2 moles of a gas at one atmosphere pressure has a greater entropy than 2 moles of the same gas at 1000 mmHg pressure.
The reaction of O3(g) to produce O2(g) has a negative entropy change.
The Sº of methane (CH4) is less than that of ethane (C2H6).
A substance can only have zero entropy at absolute zero in a perfect crystal.
(D)
(B)
(E)
(B)
(E)
(B)
crystal violet (pH range 0-2)
methyl red (pH range 4.2-6.2)
1.25 x 10-4
6.3 x 10-10
(C)
1.25 x 10-12
5.00 x 10-5
(C)
(B)
(D)
5
2.92 x 10-7
1.25 x 10-11
Qsp = 2 x 10-4 so a precipitate will be observed.
Qsp = 2 x 10-5 so a precipitate will be observed.
CHEM 1332
SPRING 2003
THIRD EXAM – APRIL, 18th – Version 4
1.
Calculate Keq at 150 ºC for the reaction, CH3OH(g) ' CO(g) + 2 H2(g), given that ΔHº = 90.9 kJ and ΔSº = 221 J/K,
(A)
0.480
2.
Once the oxidation-reduction reaction below is balanced in basic solution
(B)
2.08
(C)
13.24
(D)
2.36 x 1016
(E)
-37.7
–0.61 V
(E)
0.92 V
MnO4-(aq) + Br-(aq) ⎯→ MnO2(s) + BrO3-(aq)
(A)
(B)
(C)
(D)
(E)
The coefficient of hydroxide ions is 2, and it lies on the product side.
The coefficient of hydroxide ions is 2, and it lies on the reactant side.
The coefficient of water is 1, and it lies on the product side.
The coefficient of water is 2, and it lies on the reactant side.
None of the above.
3.
In basic solution, selenide and sulfite ions react spontaneously:
2 Se2-(aq) + 2 SO32-(aq) + 3 H2O(l) ⎯→ 2 Se(s) + 6 OH-(aq) + S2O32-(aq)
E°cell = 0.35V
If E°red (SO32-) is –0.57 V, what is E°red (Se)?
(A)
–0.22 V
(B)
+0.22 V
(C)
–0.92 V
1
D)
4.
What is the balanced equation for the cell notation:
Fe(s)⏐Fe2+(aq) NO3-(aq) ⏐NO(g) ⏐Pt(s)
(A)
(B)
(C)
(D)
(E)
Fe(s) + 2 H2O(l) + NO(g) ⎯→ Fe2+(aq) + NO3-(aq) + 4 H+(aq)
Fe2+(aq) + NO3-(aq) + 4 H+(aq) ⎯→ Fe(s) + 2 H2O(l) + NO(g)
3 Fe2+(aq) + NO(g) + 4 H2O(l) ⎯→ 3 Fe(s) + 8 H+(aq) + 2 NO3-(aq)
Fe(s) + NO3-(aq) + 4 H+(aq) ⎯→ NO(g) + Fe2+(aq) + 2 H2O(l)
3 Fe(s) + 2 NO3-(aq) + 8 H+(aq) ⎯→ 2 NO(g) + 3 Fe2+(aq) + 4 H2O(l)
5.
Consider the generalized voltaic cell shown below. Identify the following:
e-
e-
voltmeter
X
T
Z
S
Y
(i)
(ii)
(iii)
(iv)
electrode at which oxidation occurs
electrode that functions as the anode
electrode that gains mass as cell operates (assuming that a metal is produced)
the solution into which positive ions of the salt bridge will move to balance the charges
(A)
(B)
(C)
(D)
(E)
(i) X, (ii) X, (iii) T, (iv) S
(i) T, (ii) X, (iii) T, (iv) Y
(i) X, (ii) X, (iii) X, (iv) S
(i) T, (ii) T, (iii) X, (iv) S
(i) X, (ii) T, (iii)T, (iv) Y
2
6.
Consider the slightly soluble salt, barium carbonate, for which the ΔHsolution is exothermic. Which of the following statements
is TRUE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature will increase the solubility of barium carbonate in pure water.
Barium carbonate will be less soluble in acidic solution than in pure water.
Barium carbonate will be more soluble in a solution of sodium carbonate than in pure water.
Changing the pH will have no effect on the solubility of barium carbonate.
Barium carbonate will be less soluble in a solution of barium nitrate than in pure water.
7.
Calculate ΔSº for the reaction, 4 NH3(g) + 7 O2(g) → 4 NO2(g) + 6 H2O(g) given the following values of Sº in J/mol K:
Sº(NH3)
Sº(NO2)
=
=
193
240
Sº(O2)
Sº(H2O)
205
189
(A)
(D)
-113 J/K
+113 J/K
8.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
Vaporizing water has both positive ΔH and ΔS.
A process will be spontaneous if ΔSuniverse is positive.
Complex processes violate the laws of thermodynamics
ΔG for a given reaction cannot be measured directly.
A reaction can be endothermic but still be spontaneous.
9.
Calculate ΔGrxn for, 2 NOCl(g) → N2(g) + O2(g) + Cl2(g), given the following set of reactions:
(A)
(D)
(B)
(E)
=
=
-31 J/K
+1322 J/K
1/2 N2(g) + 1/2 O2(g) → NO
NO(g) + 1/2 Cl2(g) → NOCl
ΔG = 86.8 kJ
ΔG = -20.7 kJ
+66.1 kJ
-45.4 kJ
(B)
(E)
(C)
+152.9 kJ
-132.2 kJ
(C)
3
+31 J/K
+132.2 kJ
10.
Consider the reaction between CO(g) and Cl2(g) to form COCl2(g). At 298 K, ΔH = -220. kJ/mol and ΔG = -206 kJ/mol. At
what temperature will the reaction become non-spontaneous?
(A)
1.07 K
11.
Which of the following indicators would be a good choice to use in a titration of HNO3 with LiOH?
(A)
(C)
(E)
phenolphthalein (pH range 8-10)
bromothymol blue (pH range 6-7.5)
alizarin yellow (pH range 10-12)
12.
Given that the solubility of magnesium hydroxide is 3.15 x 10-2 g/L, calculate the Ksp of this salt.
(A)
(D)
9.92 x 10-4
5.82 x 10-7
13.
What is the solubility (in mol/L) of silver bromide in a solution that is 0.200 M CaBr2? Ksp of AgBr is 5.0 x 10-13.
(A)
1.00 x 10-13
14.
A solution is 2.00 x 10-3 M Ba(NO3)2 and 0.0500 M KF. Given that the Ksp of barium fluoride is 1.5 x 10-6,
(A)
(C)
(E)
Qsp = 1 x 10-4 so a precipitate will be observed.
Qsp = 1 x 10-6 so no precipitate will be observed.
Qsp = 5 x 10-6 so a precipitate will be observed.
15.
Which of the following statements is FALSE?
(A)
(B)
(C)
(D)
(E)
Increasing the temperature of a system increases the entropy.
2 moles of a gas at one atmosphere pressure has a greater entropy than 2 moles of the same gas at 1000 mmHg pressure.
The reaction of O3(g) to produce O2(g) has a negative entropy change.
The Sº of methane (CH4) is less than that of ethane (C2H6).
A substance can only have zero entropy at absolute zero in a perfect crystal.
(B)
15.7 K
(C)
(B)
(D)
(B)
(E)
(B)
1070 ºC
(C)
(C)
1.25 x 10-11
(B)
(D)
4
1070 K
(E)
4680 K
crystal violet (pH range 0-2)
methyl red (pH range 4.2-6.2)
1.25 x 10-4
6.3 x 10-10
1.25 x 10-12
(D)
(D)
2.92 x 10-7
7.07 x 10-7
(E) 5.0 x 10-5
Qsp = 2 x 10-4 so a precipitate will be observed.
Qsp = 2 x 10-5 so a precipitate will be observed.
16.
Which of the following mixtures would be classified as a buffer solution?
(A)
(B)
(C)
(D)
(E)
50 mL of 0.100 M HCl and 50 mL of 0.100 M KCl
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 25 mL of 0.100 M NaOH
50 mL of 0.100 M CH3COOH and 0.500 mL of 0.000100 M NaOH
50 mL of 0.100 M CH3COOH and 55 mL of 0.100 M HCl
17.
Calculate the pH of a solution that is 0.250 M NH3 and 0.200 M NH4Br. Kb of NH3 = 1.8 x 10-5.
(A)
4.6
18.
A buffer solution is made by mixing 40.0 mL of 0.150 M HCOOH and 20.0 mL of 0.150 M NaHCOO. 10.0 mL of 0.0500 M
NaOH is then added to the solution. What is the pH of the final solution? Ka of HCOOH = 1.8 x 10-4.
(A)
2.83 x 10-5
19.
Which of the following describes the pH at the equivalence point when a weak acid is titrated with a strong base?
(A)
(C)
(E)
The pH < 7
The pH = 7
The pH = pKa of the acid.
20.
20.0 mL of 0.25 M hydrofluoric acid (Ka = 6.8 x 10-4) is titrated with 0.150 M KOH. Calculate the pH after 15.0 mL of the
base have been added.
(A)
2.95
(B)
(B)
(B)
4.8
3.55
(C)
(C)
8.0
4.55
(B)
(D)
3.08
(C)
3.25
5
(D)
(D)
9.2
9.45
(E)
(E)
9.4
10.45
The pH > 7
The pH cannot be determined without further information
(D)
3.58
(E)
10.9