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DRAFT Do Not Use Until Posted.
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CHE 107 Summer 2018 Exam 2
Your Name: Your ID:
attachment_for_pubExamUID_lnxp115308419424244486XX_288.jpg
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Question #: 1
Which two pairs have the larger lattice energy listed first?
A. ZnS, ZnCl2
B. NaCl, MgCl2
C. Al2O3, Al2Se3
D. CsBr, LiBr
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Question #: 2
For the ionic compound KF, the steps of the Born-Haber cycle are shown. Fill in the letter that best describes the name of the enthalpy change for each step.
Reaction Enthalpy Choices
Step 1: K(s) →K(g) 1 A. ½ D, half the bond energy
Step 2: ½F2(g) → F(g) 2 B. EA, electron affinity Step 3: K(g) → K+(g) 3 C. ΔHsub Step 4: F(g) → F–(g) 4 D. IE, ionization energy Step 5: K+(g) + F–(g) → KF(s) 5 E. Lattice energy Overall: K(s) + ½F2(g) → KF(s) ΔHf .
1.
2.
3.
4.
5.
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Question #: 3
Which process is nonspontaneous?
A. Sliced fruit turning brown at room temperature.
B. Ice melting at room temperature.
C. Blue dye mixing in warm water.
D. Rusty chains (left) becoming less oxidized (right) when exposed to air and water.
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Question #: 4
Which statement is true?
A. All exothermic reactions are spontaneous.
B. All endothermic reactions are nonspontaneous.
C. Entropy increases with the number of energetically non-equivalent ways to arrange
components in a system.
D. Entropy depends only on the initial and final states, not on the path taken.
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Question #: 5
Block A has an initial temperature, TA, lower than the initial temperature of Block B, TB. What happens?
A. Heat flows from Block A to Block B; the final temperature of Block A will be equal to that
of Block B (TA = TB).
B. Heat flows from Block B to Block A; the final temperature of Block A will be equal to that
of Block B (TA = TB).
C. Heat flows from Block A to Block B; the final temperature of Block A will be less than that
of Block B (TA < TB).
D. Heat flows from Block B to Block A; the final temperature of Block A will be greater than
that of Block B (TA > TB).
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Question #: 6
Which reaction demonstrates a clear decrease in entropy?
A. 2 C6H6(l) + 15 O2(g) →12 CO2(g) + 6 H2O(g)
B. N2(g) + 3 H2(g) → 2 NH3(g)
C. 2 N2O5(g) → 2 N2(g) + 5 O2(g)
D. O2(g) + N2(g) → 2 NO(g)
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Question #: 7
The formation of crystalline sodium chloride from the elements in their standard states is a violent, spontaneous reaction: Na(s) + ½Cl2(g) → NaCl(s) ΔHº = –411 kJ The sign of the entropy change for the system, ΔSsys, is 1 [positive, negative]. The sign of the entropy change for the surroundings, ΔSsurr, is 2 [positive, negative]. The sign of the entropy change for the universe, ΔSuniv, is 3 [positive, negative].
.
1.
2.
3.
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Question #: 8
What is ΔSsublimation for dry ice, CO2(s), given Tsublimation = –78.50 °C (194.65 K) and ΔHsublimation = 25.2 kJ/mol?
ΔSsublimation = 1 J/mol·K Answer to three significant figures. Do not include units.
1.
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Question #: 9
An endothermic reaction increases in entropy. What is the most accurate way to characterize the reaction?
A. The reaction is spontaneous as written at all temperatures.
B. The reaction is spontaneous in reverse at all temperatures.
C. The reaction is spontaneous as written above a certain temperature.
D. The reaction is spontaneous as written below a certain temperature.
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Question #: 10
Given the information below, calculate ΔG°rxn for C2H6(g) + 7 Cl2(g) → 2 CCl4(g) + 6 HCl(g). .
Substance ΔG°f (kJ/mol) C2H6(g) –32.9
CCl4(g) –64.0
HCl(g) –95.3
A. –667 kJ
B. –189 kJ
C. 272 kJ
D. –780. kJ
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Question #: 11
Which choice correctly describes the solution formed?
A. χN2 = 0.78, χO2 = 0.21; nitrogen is the solute, oxygen is the solvent, and the solution is gas-
phase.
B. 10. mL methanol (CH3OH), 20. mL water; methanol is the solute, water is the solvent,
and the solution is liquid-phase.
C. 2.2 g CO2(g), 355 mL H2O(l); carbon dioxide is the solute, water is the solvent, and the
solution is gas-phase.
D. 125 g Pd(s), 2.5 g H2(g); palladium is the solute, hydrogen is the solvent, and the solution
is solid-phase.
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Question #: 12
Given the figure below, which statement is true?
A. A solution will not form.
B. Solute-solvent intermolecular forces are weaker than the solute-solute and solvent-
solvent intermolecular forces.
C. The process is not driven by entropy.
D. ΔHmix >ΔHsolute + ΔHsolvent
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Question #: 13
Using the data below, which solution is saturated at 50 ºC?
A. 1.0 g Ce2(SO4)3 in 200. g H2O
B. 10.0 g KClO3 in 50. g H2O
C. 25.0 g K2Cr2O7 in 100. g H2O
D. 95.0 g KNO3 in 200. g H2O
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Question #: 14
An aqueous solution is saturated in both O2(aq) and C6H12O6(aq) at 10 ºC. If the solution is quickly warmed to room temperature, what is most likely to occur?
.
A. Some O2 bubbles out of solution but no C6H12O6 precipitates.
B. No O2 bubbles out of solution but some C6H12O6 precipitates.
C. Some O2 bubbles out of solution and some C6H12O6 precipitates.
D. No O2 bubbles out of solution but no C6H12O6 precipitates.
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Question #: 15
What is the concentration of Xe(aq) when the partial pressure of xenon, PXe, is 2.8 atm above a solution at 20 °C? When PXe is 1.0 atm at 20 °C, the concentration is 5.0 × 10–3 M. .
A. 1.4 × 10–2 M
B. 1.5 × 10–4 M
C. 1.8 × 10–2 M
D. 1.9 × 10–3 M
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Question #: 16
Fill in the ideal van't Hoff factors for the following aqueous solutions using whole numbers. If the answer is 1, enter 1 in the blank. (NH4)2CO3 1 C12H22O11 2 Li2Cr2O7 3 Mg3(PO4)2 4
1.
2.
3.
4.
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Question #: 17
What is the vapor pressure of a solution prepared by dissolving 15.2 g of biphenyl, C12H10 (154.2
g/mol), in 55.8 g of benzene, C6H6 (78.1 g/mol), at 50.0 ºC? The vapor pressure of pure benzene, is 271 torr at 50.0 ºC and biphenyl is a nonvolatile, nonionizing
solute. 1 torr Report your answer with three significant figures. Do NOT include units in your answer.
1.
____________________________________________________________________________
Question #: 18
What is the boiling point of a solution made by dissolving 19.5 mol NaNO3 in 2.50 kg H2O? Kb(H2O) = 0.512 ºC/m and Tb = 100.0 °C for the boiling point of
pure water. Use ideal van't Hoff factors, if needed.
Report your answer with three significant figures. Do NOT include units in your answer. 1 °C
1.
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Question #: 19
Lauryl alcohol is a non-ionizing solute isolated from coconut oil to make detergents. If a solution containing 5.00 g lauryl alcohol in 0.100 kg benzene freezes at 4.10 ºC, what is the molar mass of lauryl alcohol? Kf for benzene is 5.12 °C/m and Tf for benzene is 5.50 °C. Assume ideal van't Hoff factors. .
A. 183 g/mol
B. 658 g/mol
C. 22.6 g/mol
D. 359 g/mol
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Question #: 20
The osmotic pressure of a 0.010 M CaCl2 solution is measured at 0.672 atm at 25 °C. What is imeasured and how would you expect it to change as the concentration of CaCl2 increases? .
A. imeasured = 3.00 and imeasured will increase
B. imeasured = 2.75 and imeasured will decrease
C. imeasured = 3.00 and imeasured will decrease
D. imeasured = 2.75 and imeasured will increase
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Question #: 21
N2O5 decomposes according to: 2 N2O5(g) → 4 NO2(g) + O2(g). If the rate of decomposition of N2O5 was 0.36 M/s over a given time interval, what was the rate of appearance of NO2 over the same time interval? 1 M/s Report your answer with two significant figures. Do NOT include units in your answer.
1.
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Question #: 22
Given the following reaction and data, what is the rate law for the reaction? BF3(g) + NH3(g) → F3BNH3(g) .
[BF3] (M) [NH3] (M) Initial Rate (M/s)
0.250 0.250 0.2130
0.250 0.125 0.1065
0.175 0.100 0.0596
0.350 0.100 0.1193
A. rate = k[NH3]2
B. rate = k[BF3]2[NH3]
C. rate = k[BF3][NH3]
D. rate = k[BF3]
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Question #: 23
The reaction, I–(aq) + OCl–(aq) →Cl–(aq) + OI–(aq), is found to be first-order in I–(aq) and second-order in OCl–(aq). What is the effect on the rate if the concentration of I–(aq) is doubled and the concentration of OCl–(aq) is tripled?
A. The rate increases by a factor of 6.
B. The rate increases by a factor of 12.
C. The rate increases by a factor of 18.
D. The rate increases by a factor of 24.
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Question #: 24
The decomposition of ammonia on a hot tungsten surface proceeds according to 2 NH3(g) → N2(g) + 3 H2(g) k = 3.1 × 10–4 M·s–1 How long does it take for the concentration of ammonia to decrease from 0.750 M to 0.100 M? t = 1 minutes Report your answer with two significant figures. Do NOT include units in your answer. Use the format 2.2E2 or 2.2E-2 for numbers in scientific notation.
1.
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Question #: 25
The decomposition of sulfuryl chloride, SO2Cl2, follows first-order kinetics: SO2Cl2(g) → SO2(g) + Cl2(g) t½ = 533 min at 320 ºC. If the initial concentration of SO2Cl2 is 3.27 M, what is the concentration after 6.00 hours of running this reaction at 320 °C? Report your answer to three significant figures. Do NOT include units in your answer. Use the format 2.22E2 or 2.22E-2 for numbers in scientific notation. 1 M
1.
DRAFTDo Not Use Until Posted.
CHE 107 Summer 2018 Exam 2 - Confidential
Your Name: Your ID:
attachment_for_pubExamUID_lnxp115308419424244486XX_288.jpg
Question #: 1
Which two pairs have the larger lattice energy listed first?
✓A. ZnS, ZnCl2
B. NaCl, MgCl2 ✓C. Al2O3, Al2Se3
D. CsBr, LiBr
Question #: 2
For the ionic compound KF, the steps of the Born-Haber cycle are shown. Fill in the letter that
best describes the name of the enthalpy change for each step.
Reaction Enthalpy Choices
.
1. C
2. A
3. D
4. B
5. E
Question #: 3
Which process is nonspontaneous?
A. Sliced fruit turning brown at room temperature.
B. Ice melting at room temperature.
C. Blue dye mixing in warm water.
Step 1: K(s) K(g) 1 A. ½ D, half the bond
energy
Step 2: ½F2(g) F(g) 2 B. EA, electron affinity
Step 3: K(g) K+(g) 3 C. HsubStep 4: F(g) F–(g) 4 D. IE, ionization energy
Step 5: K+(g) + F–(g) KF(s) 5 E. Lattice energy
Overall: K(s) + ½F2(g) KF(s) Hf
✓D. Rusty chains (left) becoming less oxidized (right) when exposed to air and water.
Question #: 4
Which statement is true?
A. All exothermic reactions are spontaneous. B. All endothermic reactions are nonspontaneous. C. Entropy increases with the number of energetically non-equivalent ways to arrange
components in a system. ✓D. Entropy depends only on the initial and final states, not on the path taken.
Question #: 5
Block A has an initial temperature, TA
, lower than the initial temperatureof Block B, T
B. What happens?
A. Heat flows from Block A to Block B; the final temperature of Block A will be equal to that
of Block B (TA
= TB
).
✓B. Heat flows from Block B to Block A; the final temperature of Block A will be equal to that
of Block B (TA
= TB
).
C. Heat flows from Block A to Block B; the final temperature of Block A will be less than that
of Block B (TA
< TB
).
D. Heat flows from Block B to Block A; the final temperature of Block A will be greater than
that of Block B (TA
> TB
).
Question #: 6
Which reaction demonstrates a clear decrease in entropy?
A. 2 C6H6(l) + 15 O2(g) →12 CO2(g) + 6 H2O(g)
✓B. N2(g) + 3 H2(g) → 2 NH3(g) C. 2 N2O5(g) → 2 N2(g) + 5 O2(g) D. O2(g) + N2(g) → 2 NO(g)
Question #: 7
The formation of crystalline sodium chloride from the elements in their standard states is a
violent, spontaneous reaction:
Na(s) + ½Cl2
(g) → NaCl(s) ΔHº = –411 kJ
The sign of the entropy change for the system, ΔSsys, is 1 [positive, negative].
The sign of the entropy change for the surroundings, ΔSsurr, is 2 [positive, negative].
The sign of the entropy change for the universe, ΔSuniv, is 3 [positive, negative].
.
1. negative|-|
2. positive|+|
3. positive|+|
Question #: 8
What is ΔSsublimation for dry ice, CO2(s), given Tsublimation = –78.50 °C (194.65 K) and ΔH
sublimation = 25.2 kJ/mol?
ΔSsublimation = 1 J/mol·K
Answer to three significant figures. Do not include units.
1. 129|127|128|130|130.|131|132|
Question #: 9
An endothermic reaction increases in entropy. What is the most accurate way to characterize the
reaction?
A. The reaction is spontaneous as written at all temperatures. B. The reaction is spontaneous in reverse at all temperatures.
✓C. The reaction is spontaneous as written above a certain temperature. D. The reaction is spontaneous as written below a certain temperature.
Question #: 10
Given the information below, calculate ΔG°rxn for
C2H6(g) + 7 Cl2(g) → 2 CCl4(g) + 6 HCl(g).
.
✓A. –667 kJ
B. –189 kJ C. 272 kJ D. –780. kJ
Question #: 11
Which choice correctly describes the solution formed?
Substance G°f (kJ/mol)
C2H6(g) –32.9
CCl4(g) –64.0
HCl(g) –95.3
A. χN2 = 0.78, χO2 = 0.21; nitrogen is the solute, oxygen is the solvent, and the solution is
gas-phase. ✓B. 10. mL methanol (CH3OH), 20. mL water; methanol is the solute, water is the solvent,
and the solution is liquid-phase. C. 2.2 g CO2(g), 355 mL H2O(l); carbon dioxide is the solute, water is the solvent, and the
solution is gas-phase. D. 125 g Pd(s), 2.5 g H2(g); palladium is the solute, hydrogen is the solvent, and the solution
is solid-phase.
Question #: 12
Given the figure below, which statement is true?
A. A solution will not form.
✓B. Solute-solvent intermolecular forces are weaker than the solute-solute and solvent-solvent intermolecular forces.
C. The process is not driven by entropy. D. ΔHmix >ΔHsolute + ΔHsolvent
Question #: 13
Using the data below, which solution is saturated at 50 ºC?
A. 1.0 g Ce2(SO4)3 in 200. g H2O
✓B. 10.0 g KClO3 in 50. g H2O C. 25.0 g K2Cr2O7 in 100. g H2O D. 95.0 g KNO3 in 200. g H2O
Question #: 14
An aqueous solution is saturated in both O2(aq) and C6H12O6(aq) at 10 ºC. If the solution is
quickly warmed to room temperature, what is most likely to occur?
.
✓A. Some O2 bubbles out of solution but no C
6H
12O
6 precipitates.
B. No O2 bubbles out of solution but some C6
H12
O6
precipitates. C. Some O2 bubbles out of solution and some C
6H
12O
6 precipitates.
D. No O2 bubbles out of solution but no C6
H12
O6
precipitates.
Question #: 15
What is the concentration of Xe(aq) when the partial pressure of xenon, PXe, is 2.8 atm above a
solution at 20 °C? When PXe is 1.0 atm at 20 °C, the concentration is 5.0 × 10–3 M.
.
✓A. 1.4 × 10–2
M B. 1.5 × 10–4
M C. 1.8 × 10–2
M D. 1.9 × 10–3
M
Question #: 16
Fill in the ideal van't Hoff factors for the following aqueous solutions using whole numbers. If
the answer is 1, enter 1 in the blank.
(NH4)2CO3 1
C12H22O11 2
Li2Cr2O7 3
Mg3(PO4)2 4
1. 3|three|
2. 1|one|
3. 3|three|
4. 5|five|
Question #: 17
What is the vapor pressure of a solution prepared by dissolving 15.2 g of biphenyl, C12H10 (154.2 g/mol), in 55.8 g of benzene, C
6H
6 (78.1 g/mol), at 50.0 ºC? The vapor
pressure of pure benzene, is 271 torr at 50.0 ºC and biphenyl is a nonvolatile,
nonionizing solute.
1 torr
Report your answer with three significant figures. Do NOT include units in your answer.
1. 238
Question #: 18
What is the boiling point of a solution made by dissolving 19.5 mol NaNO3 in 2.50 kg H2O? Kb(H2O) = 0.512 ºC/m and Tb = 100.0 °C for the boiling point of
pure water. Use ideal van't Hoff factors, if needed.
Report your answer with three significant figures. Do NOT includeunits in your answer.
1 °C
1. 108
Question #: 19
Lauryl alcohol is a non-ionizing solute isolated from coconut oil to make detergents. If a solution
containing 5.00 g lauryl alcohol in 0.100 kg benzene freezes at 4.10 ºC, what is the molar mass of
lauryl alcohol? Kf for benzene is 5.12 °C/m and T
f for benzene is 5.50 °C. Assume ideal van't Hoff
factors.
.
✓A. 183 g/mol
B. 658 g/mol C. 22.6 g/mol D. 359 g/mol
Question #: 20
The osmotic pressure of a 0.010 M CaCl2 solution is measured at 0.672 atm at 25 °C. What is i
measured and how would you expect it to change as the concentration of CaCl2 increases?
.
A. imeasured = 3.00 and imeasured will increase
✓B. imeasured = 2.75 and imeasured will decrease C. imeasured = 3.00 and imeasured will decrease D. imeasured = 2.75 and imeasured will increase
Question #: 21
N2O5 decomposes according to:
2 N2O5(g) → 4 NO2(g) + O2(g).
If the rate of decomposition of N2O5 was 0.36 M/s over a given time interval, what was the rate
of appearance of NO2 over the same time interval?
1 M/s
Report your answer with two significant figures. Do NOT include units in your answer.
1. 0.72
Question #: 22
Given the following reaction and data, what is the rate law for the reaction?
BF3(g) + NH3(g) → F3BNH3(g)
.
[BF3] (M) [NH3] (M)Initial Rate
(M/s)
0.250 0.250 0.2130
0.250 0.125 0.1065
0.175 0.100 0.0596
0.350 0.100 0.1193
A. rate = k[NH3]2
B. rate = k[BF3]2[NH3]
✓C. rate = k[BF3][NH3] D. rate = k[BF3]
Question #: 23
The reaction,
I–(aq) + OCl–(aq) →Cl–(aq) + OI–(aq),
is found to be first-order in I–(aq) and second-order in OCl–(aq). What is the effect on the rate
if the concentration of I–(aq) is doubled and the concentration of OCl–(aq) is tripled?
A. The rate increases by a factor of 6. B. The rate increases by a factor of 12.
✓C. The rate increases by a factor of 18. D. The rate increases by a factor of 24.
Question #: 24
The decomposition of ammonia on a hot tungsten surface proceeds according to
2 NH3(g) → N2(g) + 3 H2(g) k = 3.1 × 10–4 M·s–1
How long does it take for the concentration of ammonia to decrease from 0.750 M to 0.100 M?
t = 1 minutes
Report your answer with two significant figures. Do NOT include units in your answer. Use the
format 2.2E2 or 2.2E-2 for numbers in scientific notation.
1. 35|34|36|
Question #: 25
The decomposition of sulfuryl chloride, SO2Cl2, follows first-order kinetics:
SO2Cl2(g) → SO2(g) + Cl2(g) t½ = 533 min at 320 ºC.
If the initial concentration of SO2Cl2 is 3.27 M, what is the concentration after 6.00 hours of
running this reaction at 320 °C?
Report your answer to three significant figures. Do NOT include units in your answer. Use the
format 2.22E2 or 2.22E-2 for numbers in scientific notation.
1 M
1. 2.05|2.04|2.03|2.02|2.01|2.06|2.07|2.08|2.09|
