Chemistry 112 Name _______________________

Exam I Form A Section _______________________

February 3, 2015 eMail _______________________

IMPORTANT: On the scantron (answer sheet), you MUST clearly fill your name, your student number, section number, and test form (white cover = test form A; yellow cover = test form B). Use a #2 pencil.

There are 25 questions on this exam. Check that you have done all of the problems and filled in the first 25 bubbles on the scantron.Your score will be reported in percent (max 100%).

Exam policy

• Calculators with text-programmable memory are not allowed. • Relevant data and formulas, including the periodic table, are attached at the end of this exam. • Your grade will be based only on what is on the scantron form. • The answer key will be posted on the web after the exam (on the Exam Schedule page). • You must turn in your cover sheet with your scantron answer form.

Hints

• As you read the question, underline or circle key words to highlight them for yourself. Avoid errors from "mis-reading" the question.

• Pay attention to units and magnitudes (decimal places) of numbers obtained from calculations. • There is no penalty for guessing.

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CHEMISTRY 112 EXAM 1 Feb. 3, 2015

FORM A ------------------------------------------------------------------------------------------------------------------------------- 1. A gas phase reaction is studied and the activation energy and reaction energy are

determined. Which of the following reaction profiles is consistent with this information?

Ea = 20 kJ/mol, ∆E = + 7.5 kJ/mol

A. B.

C. D.

E.

-------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 2. When N2O5(g) decomposes as shown below at a fixed temperature, the rate of formation of

NO2 is 3.7 × 10−3 M/s

2 N2O5(g) → 4 NO2(g) + O2(g)

What is the rate of loss of N2O5 under these conditions?

A. 9.3 × 10−4 M/s

B. 1.9 × 10−3 M/s

C. 3.7 × 10−3 M/s

D. 7.4 × 10−3 M/s

E. 1.5 × 10−2 M/s ------------------------------------------------------------------------------------------------------------------------------- 3. The rate law for the following reaction is rate = k [NO]2[H2]

2 NO(g) + 2 H2(g) → N2(g) + 2 H2O(g)

If the concentration of NO is tripled, while everything else is kept the same, what will happen to the rate of the reaction?

A. It remains unchanged.

B. It triples.

C. It is reduced by a factor of 3.

D. It increases by a factor of 6.

E. It increases by a factor of 9. ------------------------------------------------------------------------------------------------------------------------------- 4. The experimentally determined rate law for the following reaction is:

rate = k [Cl2]½

[CHCl3]

Cl2(g) + CHCl3(g) →HCl(g) + CCl4(g)

What is the unit of the rate constant for this reaction?

A. M s−1 B. M−1 s−1

C. M–½ s−1

D. M½

s−1

E. M−½ s−½

-------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 5. One way enzyme catalysts increase the rate of reactions is by:

A. decreasing the energy of the products.

B. shifting the equilibrium to favor product formation.

C. increasing the temperature during the reaction.

D. decreasing the activation energy of the reaction.

E. increasing the activation energy of the reaction. ------------------------------------------------------------------------------------------------------------------------------- 6. The isotope cadmium-116 is most likely to decay by which of the following decay modes?

A. alpha decay

B. beta decay

C. electron capture

D. positron emission

E. Both C and D ------------------------------------------------------------------------------------------------------------------------------- 7. An atom of 238U undergoes 6 rounds of alpha decay and 5 rounds of beta decay. What is

the resultant isotope?

A. 214Bi

B. 214Re

C. 226At

D. 226Re

E. 214At ------------------------------------------------------------------------------------------------------------------------------- 8. Why do the rates of reactions increase when the concentrations of reactants are increased?

A. There is an increase in the magnitude of the rate constant.

B. The average kinetic energy of the reactants increases.

C. It ensures that all of the reactants will collide with the proper orientation for reaction.

D. It lowers the energy of the transition state.

E. It increases the frequency of collisions. -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 9. An experiment was run at 298 K and the following data were collected and plotted:

The slope is –0.014 s–1 and the y-intercept is –0.2867. What is the order of the reaction, and what is the half-life?

Order Half-life A. second 49.5 sec

B. second 0.014 sec

C. first 2.4 sec

D. first 49.5 sec

E. first 0.014 sec ------------------------------------------------------------------------------------------------------------------------------- 10. A first-order reaction is 4 times faster at 50°C than it is at 25°C. What is the activation

energy of this reaction?

A. 0.576 kJ/mol

B. 5.34 kJ/mol

C. 26.1 kJ/mol

D. 44.3 kJ/mol

E. 52.2 kJ/mol -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 11. The following data was collected for the recombination reaction of iodine atoms in the

presence of Ar. What is the rate law for this reaction?

2 I(g) + Ar(g) → I2(g) + Ar(g)

[I] (M) [Ar] (M) Initial rate (M/s) 1.0 × 10–5 1.0 × 10–3 8.7 × 10–4 2.0 × 10–5 1.0 × 10–3 3.5 × 10–3 4.0 × 10–5 1.0 × 10–3 1.4 × 10–2 2.0 × 10–5 4.0 × 10–3 1.4 × 10–2

A. rate = k [I] [Ar]

B. rate = k [I]2

C. rate = k [Ar]

D. rate = k [I]

E. rate = k [I]2[Ar] ------------------------------------------------------------------------------------------------------------------------------- 12. The progress of a reaction of A → 2 B is shown below. Each white sphere represents

1.0 × 10–2 M of A, each gray sphere represents 1.0 × 10–2 M of B. What is the average rate of disappearance of A during this time interval?

t = 0 s t = 35 s

A. 1.4 × 10–3 M s–1

B. 2.9 × 10–3 M s–1

C. −1.4 × 10–3 M s–1

D. −2.9 × 10–3 M s–1

E. 7.1 × 10–4 M s–1 -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 13. The observed rate law for the reaction: 2 NO (g) + Br2 (g) → 2 NOBr (g) is

Rate = k [NO]2[Br2]

Which of the following mechanisms is/are consistent with the observed rate law?

Mechanism I: NO (g) + Br2 (g) ⇌ NOBr2 (g) (fast) NOBr2 (g) + NO (g) → 2 NOBr (g) (slow) Mechanism II: NO (g) + Br2 (g) → NOBr2 (g) (slow) NOBr2 (g) + NO (g) → 2 NOBr (g) (fast) Mechanism III: NO (g) + NO (g) ⇌ N2O2 (g) (fast) N2O2 (g) + Br2 (g) → 2 NOBr (g) (slow)

A. I only

B. II only

C. III only

D. I and III only

E. II and III only ------------------------------------------------------------------------------------------------------------------------------- 14. Dr. Rick T. Cat, a famous scientist, and his team of intrepid graduate students invent a new

element, Nittnium. One isotope of Nittnium is radioactive and decays with a half-life of 409 seconds. At this rate, how long will it take for 87.5% of a sample to be consumed?

A. 79 sec

B. 358 sec

C. 562 sec

D. 818 sec

E. 1,227 sec -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 15. Each line in the graph below represents a different reaction. Rank the reactions in order of increasing activation energy.

A. 1 < 2 < 3

B. 1 < 3 < 2

C. 2 < 3 < 1

D. 3 < 1 < 2

E. 3 < 2 < 1

------------------------------------------------------------------------------------------------------------------------------- 16. A wooden artifact discovered in the Sahara desert by Rick T. Cat is sent to the lab to be

carbon dated. It possesses a 14C activity of 10.2 disintegrations per second. Given that the half-life of 14C is 5,715 years and the activity of an equal mass of freshly cut wood has a constant value of 15.2 disintegrations per second, how old is the artifact?

A. 1.9 × 106 years

B. 1,234 years

C. 10,928 years

D. 4,230 years

E. 3,290 years -------------------------------------------------------------------------------------------------------------------------------

Rxn 1: Rxn 2: Rxn 3:

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------------------------------------------------------------------------------------------------------------------------------- 17. Butadiene (C4H6) is used mainly in the production of synthetic rubber. A reaction of C4H6 was studied at 326 °C, and the results (1/[C4H6] as a function of time) are shown in the figure below.

The y-intercept of the plot is 58.1 M–1, and the slope of the line is 0.0131 s–1. If the experiment is repeated with an initial C4H6 concentration of 0.0325 M, how long would it take to decompose half of the C4H6?

A. 2.35 × 103 sec

B. 1.22 × 103 sec

C. 3.64 × 103 sec

D. 4.21 × 103 sec

E. 5.10 × 103 sec -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 18. A student studies a first order reaction under several different conditions and gets the

results shown in the plot below. Which of the following conclusions about these experiments are correct?

ln[A

]

Time

3

2

1

1. Reactions 1 and 2 were done at the same temperature but with different starting concentrations.

2. Reactions 2 and 3 were done at the same temperature but with different starting concentrations.

3. Reaction 2 was done at a lower temperature than reaction 3. A. only 1 is correct

B. only 2 is correct

C. only 3 is correct

D. 1 and 3 are correct.

E. 2 and 3 are correct. -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- For the next two questions, consider the following mechanism which involves the oxidation of iodide ion by hydrogen peroxide in acid solution: Step 1 (slow) H2O2(aq) + I–(aq) H2O(l) + OI–(aq) Step 2 (fast) H+(aq) + OI–(aq) HOI(aq) Step 3 (fast) HOI(aq) + H+(aq) + I–(aq) I2(aq) + H2O(l)

--------------------------------------------------------------------------

19. Which of the following statements are true?

A. OI– and HOI are catalysts

B. OI– and HOI are intermediates

C. OI– is a catalyst and HOI is an intermediate

D. HOI is a catalyst and OI– is an intermediate

E. There are no catalysts or intermediates in this mechanism.

-------------------------------------------------------------------------- 20. For the mechanism above to be consistent with the kinetic data, what must be the

experimental rate law?

A. Rate = k [H2O2][H+]2[I–]2

B. Rate = k [I2][H2O]2

C. Rate = k [H2O2][I–]

D. Rate = k [H+][OI–]

E. Rate = k [HOI][H+][I–] -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 21. The following graph depicts the belt of stability:

Which one of the following statements concerning nuclear decay processes is TRUE?

A. A 1:1 neutron-to-proton ratio is ideal for maximum nuclear stability for ALL elements on the periodic table.

B. Isotopes above the belt have too many neutrons; during decay neutrons are converted into protons.

C. Isotopes below the belt have too many neutrons; during decay electrons are captured and converted into protons.

D. Isotopes that decay via positron emission convert neutrons into protons.

E. No element undergoes alpha decay unless bombarded with neutrons in a nuclear reactor.

-------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 22. What is the nuclear binding energy of iron-56 in kJ/mol?

The mass of the iron-56 nucleus is 55.92068 amu.

A. 7.90 × 10–11 kJ/mol

B. 4.76 × 1010 kJ/mol

C. 2.78 × 109 kJ/mol

D. 8.78 × 10–28 kJ/mol

E. 5.38 × 1012 kJ/mol ------------------------------------------------------------------------------------------------------------------------------- 23. The activation energy for the industrial drying of tomato, an important method of food

preservation, is 33.3 kJ/mol. How many times faster does this process proceed at 200°C than at 25°C?

A. 1.2

B. 5.0

C. 144

D. 1.31 × 104

E. 7.6 × 1060 ------------------------------------------------------------------------------------------------------------------------------- 24. Rick T. Cat participated in the first manned mission to Mars! He collected a mineral sample

from Mars to send back to earth for analysis. It contains 68 mg of uranium-235 and 22 mg of lead-206. Assuming that the mineral sample started as pure uranium-235, what is the age of the Martian rock? The half-life process for uranium-235 → lead-206 is 4.5 × 109 years.

A. 7.33 × 109 years

B. 2.74 × 1010 years

C. 2.06 × 109 years

D. 5.92 × 105 years

E. 4.09 × 108 years -------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------- 25. In organic chemistry, cis/trans isomerism describes the relative orientation of functional groups within a molecule. Alkene containing compound but-2-ene can interconvert from the cis isomer to the trans isomer at 80 oC with an activation energy of 65.0 kJ/mol. At the same temperature with a nitric oxide (NO) catalyst, the activation energy decreases to 27.5 kJ/mol. Assuming the frequency factor is the same for the catalyzed and uncatalyzed reactions, how many times faster is the catalyzed reaction than the uncatalyzed reaction at 80 oC?

A. 3.5 × 105

B. 2.8 × 10–6

C. 5.1 × 108

D. 1.0 × 1010

E. 1.7 × 10–2 ------------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------

END OF EXAM

cis-but-2-ene trans-but-2-ene

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CH

EM 112 Sp15

Exam 1 - Form

A

Scrap Paper

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CHEM 112 Sp15 Exam 1 - Form A

Scrap Paper

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Chem 112 Equations Constants, Conversions And Equations For Use During Exams And Quizzes

 

Conversions    Constants 

1J kg m2 s2 C V     c 2.99792458 108 m s1    R 0.08206 L atm mol1 K1 

1A C s1    h 6.63 1034 J s     R 8.314 J mol1 K1 

1g 6.021023 amu    F 96,485 C mol1    01 n 1.0086649 amu  

    NA 6.0221023 mol1     1

1 p 1.0072765 amu  

    KW 11014 at 25 oC      

Equations 

k Ae

Ea

RT

 Rate kN   G H TS nFE  

ln k E

a

RT ln A   ln

Nt

N0

0.693t

t1 2

kt   Go 2.303 RT log K RT ln K  

ln A ln A 0 kt   E= h hc

  G Go RT ln Q  

lnk

1

k2

E

a

R

1T

2

1T

1

  E = mc2   G Go 2.303 RT log Q  

t1 2

ln2k

0.693

k  K

aK

b K

W H OH   Eo

0.0592n

log K at 25 oC  

1A

1

A 0

kt   pH pKa log

X HX

  E Eo 0.0592

nlog Q at 25 oC  

Kp

= Kc

RT n pKW pHpOH pK

a pK

b  

Molecular Orbital Theory Diagrams  Crystal Field Theory Diagram                                        Color Wheel with Wavelength Ranges                                                         

   

PERIODIC TABLE of the ELEMENTS MAIN GROUPS MAIN GROUPS

1A 1

8A 18

1 H

1.008

2A 2

3A 13

4A 14

5A 15

6A 16

7A 17

2 He

4.003

3 Li

6.941

4 Be

9.012

TRANSITION METALS

5 B

10.811

6 C

12.011

7 N

14.007

8 O

15.999

9 F

18.998

10 Ne

20.180

11 Na

22.990

12 Mg

24.305

3B 3

4B 4

5B 5

6B 6

7B 7

8B 8

8B 9

8B 10

1B 11

2B 12

13 Al

26.982

14 Si

28.086

15 P

30.974

16 S

32.066

17 Cl

35.453

18 Ar

39.948

19 K

39.098

20 Ca

40.078

21 Sc

44.956

22 Ti

47.867

23 V

50.942

24 Cr

51.996

25 Mn

54.938

26 Fe

55.845

27 Co

58.933

28 Ni

58.693

29 Cu

63.546

30 Zn

65.39

31 Ga

69.723

32 Ge 72.61

33 As

74.992

34 Se

78.96

35 Br

79.904

36 Kr

83.80

37 Rb

85.468

38 Sr

87.62

39 Y

88.906

40 Zr

91.224

41 Nb

92.906

42 Mo 95.94

43 Tc [98]

44 Ru

101.07

45 Rh

102.90

46 Pd

106.42

47 Ag

107.87

48 Cd

112.41

49 In

114.82

50 Sn

118.71

51 Sb

121.76

52 Te

127.60

53 I

126.90

54 Xe

131.29

55 Cs

132.91

56 Ba

137.33

57 La*

138.91

72 Hf

178.49

73 Ta

180.95

74 W

183.84

75 Re

186.21

76 Os

190.23

77 Ir

192.22

78 Pt

195.08

79 Au

196.97

80 Hg

200.59

81 Tl

204.38

82 Pb

207.2

83 Bi

208.98

84 Po [209]

85 At

[210]

86 Rn [222]

87 Fr

[223]

88 Ra [226]

89 Ac** [227]

104 Rf

[261]

105 Db [262]

106 Sg [266]

107 Bh [264]

108 Hs [265]

109 Mt [268]

110

[269]

111

[272]

112

[277]

114

[285]

116

[289]

118

[293]

* LANTHANOIDS 58 Ce

140.12

59 Pr

140.91

60 Nd

144.24

61 Pm [145]

62 Sm

150.36

63 Eu

151.96

64 Gd

157.25

65 Tb

158.92

66 Dy

162.50

67 Ho

164.93

68 Er

167.26

69 Tm

168.93

70 Yb

173.04

71 Lu

174.97

** ACTINOIDS

90 Th

232.04

91 Pa

231.04

92 U

238.03

93 Np [237]

94 Pu [244]

95 Am [243]

96 Cm [247]

97 Bk [247]

98 Cf

[251]

99 Es [252]

100 Fm [257]

101 Md [258]

102 No [259]

103 Lr

[262]