Chemistry 106 Fall 2006 Exam 2 Form A
1. When 5.000 grams of RbClO4 are dissolved in 25.00 g of water, the temperature drops
from 25.00ºC initially to 14.53ºC. What is ΔHsoln for RbClO4? Heat capacity of water is
C(H2O) = 4.184 J•g-1•˚C-1.
A. 0.2190 kJ/mol
C. -40.50 kJ/mol
E. 40.50 kJ/mol
B. -10.96 kJ/mol
D. 10.96 kJ/mol
2. Which of the following will have a heat of hydration that is greater than Na+ ?
A. Rb+
B. Be2+
C. I-
D. Cu+
E. K+
3. The sign and magnitude of ΔHsoln depends on
A.
B.
C.
D.
solvent-solvent intermolecular forces.
solute-solvent intermolecular forces.
solute-solute intermolecular forces.
all the above.
4. According to the second law of thermodynamics, the change in the entropy of the universe
(ΔSuniv) during a spontaneous reaction is
A.
B.
C.
D.
E.
negative.
zero.
less than the change in entropy of the system (ΔSsys).
random
positive.
5. Determine ΔSrxn for
H2 (g) + I2 (g)
2HI (g)
given
Substance
H2 (g)
I2 (g)
HI (g)
S∫ (J/mol K)
130.58
116.73
206.3
A. -165.29 J/K mol
C. 165.29 J/K mol
E. 206.3 J/K mol
B. 398.75 J/K mol
D. -41.10 J/K mol
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Chemistry 106 Fall 2006 Exam 2 Form A
6. Processes with __________ are always spontaneous.
A.
B.
C.
D.
E.
ΔH > 0 and ΔS > 0
ΔH > 0 and ΔS < 0
ΔH < 0 and ΔS < 0
ΔH < 0 and ΔS > 0
All of the above
7. Hydrogen reacts with nitrogen to form ammonia (NH3) according to the reaction
3H2 (g) + N2 (g)
2NH3 (g)
The value of ΔHº is -92.38 kJ/mol and ΔSº is -198.2 J/K mol. Determine ΔGº at 298 K.
A.
B.
C.
D.
E.
105.8 kJ/mol
5.897 × 104 kJ/mol
-16.66 kJ/mol
297.8 kJ/mol
-33.32 kJ/mol
8. Which of the following processes will lead to a positive change in entropy of the system?
A.
B.
C.
D.
E.
Sodium chloride crystals form as salt water evaporates.
Stalactites form in a cave.
Helium gas escapes from the hole in a balloon.
A model airplane is put together.
None of the above
9. Which of the following will have the greatest standard molar entropy (Sº)?
A. He (g)
E. C (s, graphite)
C. NH3 (g)
B. H2O(l )
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D. NaCl(s)
Chemistry 106 Fall 2006 Exam 2 Form A
10. What is the maximum amount of work (∆GoRXN) that can be done by the reaction:
C H4 (g) + 2 O2 (g)
CO2 (g) + 2H2 O(g)
given
Substance
CH4 (g)
CO2 (g)
H2O (g)
A.
B.
C.
D.
E.
ΔGºf (kJ/mol)
-50.8
-394.4
- 228.57
Not enough information is provided to answer this question.
-50.8 kJ/mol
-749.9 kJ/mol
572.1 kJ/mol
-800.7 kJ/mol
11. The formation of triglycerides from fatty acids and glycerol produces __________ in
addition to the triglyceride:
B. water (H2O)
D. ammonia (NH3)
A. an acid (H+ )
C. methane (CH4)
E. none of the above
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Chemistry 106 Fall 2006 Exam 2 Form A
12. Which of the following compounds is not an α-amino acid?
A.
B.
C.
D.
E. None are α-amino acids
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Chemistry 106 Fall 2006 Exam 2 Form A
13. Which of the following molecules contains one or more chiral centers? In other words: which
molecules have enantiomers?
A.
B. H2CClBr
C.
D.
E. All of the above
14. A two tablespoon (35 g) serving of peanut butter contains 12 g of fat and a total of 140
Calories. Calculate the number of Calories from fat in the serving. Assume fat has a fuel value
of 38 kJ/g (1 Cal = 4.184 kJ).
A. 65 Calories
C. 109 Calories
E. 33 Calories
B. 9 Calories
D. 456 Calories
15. The fifth step in the catabolism of glucose is the reaction:
C3H2O2(OPO3)24 - + H2O ––––> C3H2O4HOPO32 - + HPO42-
∆G = ?
Simultaneously the body uses the HPO42- ion in the following reaction:
ADP + HPO42- ––––> ATP + H2O
∆G = 30.5 kJ
Which statement about the process is true?
A.
B.
C.
D.
E.
The ∆G > 0 for the first reaction and the overall process is spontaneous.
The ∆G = -30.5 kJ for the first reaction and the overall process is spontaneous.
The ∆G < 0 for the first reaction and the overall process is spontaneous.
The ∆G > 0 for the first reaction and the overall process is nonspontaneous.
The ∆G < 0 for the first reaction and the overall process is nonspontaneous.
16. The subunits of the backbone of DNA are:
A.
B.
C.
D.
E.
carboxylic acids
peptides
sugars
fatty acids
amines
Page 5
Chemistry 106 Fall 2006 Exam 2 Form A
17. The rate of disappearance of HI in the reaction 2 HI (g) → I2 (g) + H2 (g) is shown in the
figure below. What is the instantaneous rate of this reaction at t = 5 sec?
A. -0.025 M/s
C. -0.100 M/s
E. -0.125 M/s
B. -0.005 M/s
D. -0.010 M/s
18. Indicate which of the following compounds is not a component of photochemical smog:
A. NO2
C. H2O
E. they all are components of smog
B. NO
D. O3
19. For the reaction
2CH3CH3(g) + 7O2(g) ---> 4CO2(g) + 6H2O(g)
which expression correctly indicates the relation between the rates of change of CH3CH3
concentratin and H2O concentration?
A.
B.
C.
D.
E.
-3∆[CH3CH3]/∆t = ∆[H2O]/∆t
∆[CH3CH3]/∆t = 6∆[H2O]/∆t
-∆[CH3CH3]/∆t = ∆[H2O]/∆t
-6∆[CH3CH3]/∆t = ∆[H2O]/∆t
-∆[CH3CH3]/∆t = 4∆[H2O]/∆t
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Chemistry 106 Fall 2006 Exam 2 Form A
20. HI dissociates to form I2 and H2:
2 HI (g) → H2 (g) + I2 (g).
If the concentration of HI changes at a rate of -0.45 M/s, what is the rate of appearance of
I2 (g)?
A. 0.90 M/s
C. 0.23 M/s
E. 0.45 M/s
B. -0.23 M/s
D. -0.45 M/s
21. In the combustion of methane
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g)
which reactant has the greatest rate of disappearance?
A. O2
C. CO2
E. All disappear at the same rate
B. CH4
D. H2O
22. The reaction
A + 2B → C
is first order in B and second order in a. The overall order of the reaction is
A. 3rd.
B. 2nd.
C. 1st.
D. 0th.
E. 4th.
23. The reaction 2 NO (g) + O2 (g) → 2 NO2 (g) has the rate law Rate = k[O2][NO]2. If the
concentration of NO is reduced by a factor of two, the rate will
A.
B.
C.
D.
E.
double.
be reduced by a factor of 4.
be increased by a factor of 4
remain the same.
be reduced by a factor of 2.
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Chemistry 106 Fall 2006 Exam 2 Form A
24. Which of the following plots indicates the reaction is second order?
A.
B.
C.
D.
E. All of the above could be second order.
25. What are the units of the rate constant for a first-order reaction?
A. M/s
B. 1/(Ms)
C. 1/(Ms2)
D. 1/(M2s)
E. 1/s
26. The first order reaction A → B, has k = 5.67 s-1. If [A]0 = 0.500 M, how long will it take
[A] = 0.124 M?
A. 8.18 s
B. 0.246 s
C. 0.488 s
D. 0.123 s
E. 0.100 s
27. Determine the overall order of the reaction: H2 (g) + 2 ICl (g) → I2 (g) + 2 HCl (g)
from the following data (remember P, pressure, is proportional to concentration):
Experiment
1
2
3
A. 4th
[H2] (torr)
250
250
50
[ICl] (torr)
325
81
325
B. 3rd
C. 1st
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Rate (torr/s)
1.34
0.331
0.266
D. 2nd
E. 0th
Chemistry 106 Fall 2006 Exam 2 Form A
28. Given the following data, determine the rate constant, k, of the reaction:
H2 (g) + 2 ICl (g) → I2 (g) + 2 HCl (g):
Experiment
1
2
3
[H2] (torr)
250
250
50
[ICl] (torr)
325
81
325
Rate (torr/s)
1.34
0.331
0.266
A. 6.06 × 104 torr-1s-1
C. 8.17 × 10-5 torr-1s-1
E. 3.03 × 10-5 torr-1s-1
B. 1.65 × 10-5 torr-1s-1
D. 1.34 torr-1s-1
Page 9
Chemistry 106 Fall 2006 Exam 2 Form A
Energy profiles for four different reactions
29. Which of the reactions will have the largest rate constant?
A. III
B. IV
C. II
D. I
E. All the same
30. The reaction NO2 (g) + CO (g) → NO (g) + CO2 (g) is thought to occur by the following
mechanism:
Step 1: NO2 (g) + NO2 (g) → NO3 (g) + NO (g)
Step 2: NO3 (g) + CO (g) → NO2 (g) + CO2 (g)
Which of the following species is an intermediate?
A. NO3
B. NO
C. CO2
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D. CO
E. NO2
Chemistry 106 Fall 2006 Exam 2 Form A
31. Given the following data for the reaction A → B, determine the activation energy, Ea, of the
reaction.
k(M/s)
T(K)
4.05 x 10-3
350
6.78 x 10-3
400
A. 0.699 J/mol
C. 172 J/mol
E. 5.81 J/mol
B. 11.9 kJ/mol
D. 1.43 kJ/mol
32. Which point on the energy profile below is the transition state?
A. III
B. II
C. V
D. IV
33. A proposed mechanism for the reaction H2 + 2ICl ---> I2 + 2HCl is
H2 + ICl ---> HI + HCl
HI + ICl ---> I2 + HCl
slow
fast.
What is the molecularity of the rate determining step?
A.
B.
C.
D.
E.
zero-molecular
bimolecular
termolecular
unimolecular
need more information.
Page 11
E. I
Chemistry 106 Fall 2006 Exam 2 Form A
34. The mechanism for the first-order reaction
Step 1: H2O2 (aq) + I− (aq ) → H2O(l ) + OI− (aq)
(slow)
Step 2: H2O2 (aq) + OI− (aq) → H2O(l ) + O2(g) + I− (aq) (fast)
Identify the catalyst in the reaction.
A. H2O2
B. O2
C. H2O
D. OI-
E. I-
35. A proposed mechanism for the reaction H2 + 2ICl ---> I2 + 2HCl is
H2 + ICl ---> HI + HCl
HI + ICl ---> I2 + HCl
slow
fast.
What is the rate law for the second fast step?
A.
B.
C.
D.
E.
R = k[I2][HCl]
R = k([HI][ICl]-[I2][HCl])
R = k[HI][ICl]2
R = k[HI][ICl]
R = k[HI]2[ICl]
36. Which of the following reaction pathways shows the effect of a catalyst (black) on an
uncatalyzed reaction (gray)?
A.
B.
C.
D.
Page 12
Answer Key for Test “Exam 2 F06 Form A”, 10/17/07
No. in No. on
Q-Bank Test Correct Answer
13 10
13 7
13 5
13 16
13 35
13 46
13 49
13 22
13 20
13 55
13 85
13 64
13 84
13 75
13 87
13 91
14 18
14 3
14 98
14 14
14 11
14 26
14 21
14 43
14 25
14 47
14 30
14 40
14 65
14 55
14 84
14 64
14 99
14 94
14 100
14 96
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
E
B
D
E
C
D
E
C
C
E
B
D
A
C
C
C
D
C
A
C
A
A
B
D
E
B
D
B
A
A
B
A
B
E
D
B
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