Chemistry 112 Name _______________________

Exam I Form A Section _______________________

January 29, 2013 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%).

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Calculators with text-programmable memory are not allowed. Relevant data and formulas, including the periodic table, are attached at the end of this

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There is no penalty for guessing.

CHEMISTRY 112 EXAM 1 January 29, 2013

FORM A ------------------------------------------------------------------------------------------------------------------------------- 1. Consider the following reaction:

A + B → C Rate = k[B]2

Which of the following will NOT increase the reaction rate?

A. Increasing the concentration of A

B. Increasing the concentration of B

C. Raising the reaction temperature

D. Adding a suitable catalyst

E. All of the above changes will result in an increase in reaction rate ------------------------------------------------------------------------------------------------------------------------------- 2. A possible mechanism for the reaction of hydrogen bromide with oxygen is: HBr (g) + O2(g) HOOBr (g) step 1

HOOBr (g) + HBr (g) 2 HOBr (g) step 2

HOBr (g) + HBr (g) H2O (g) + Br2 (g) step 3

Which of the following is an intermediate in this reaction?

A. HOOBr only

B. HBr and O2 only

C. HOBr only

D. HOOBr and HBr only

E. Br2, HOBr and HOOBr only ------------------------------------------------------------------------------------------------------------------------------- 3. Which one of the following statements about rate constant k is FALSE? A. k is dependent on the concentration of the reactants.

B. k increases with increasing temperature.

C. k decreases with increasing activation energy.

D. k can be increased by adding a catalyst.

E. The reaction rate is directly proportional to k. -------------------------------------------------------------------------------------------------------------------------------

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

4. For the reaction below, = 2.5 x 10–2 atm/s, where ΔP(H2) is the change in pressure of

hydrogen. What is the rate of loss of C6H14 (defined as ) for this reaction for the same time

period?

C6H14 (g) → C6H6 (g) + 4 H2 (g)

A. 2.5 x 10–2 atm/s

B. 6.25 x 10–3 atm/s

C. 2.5 x 10–2 atm/s

D. 0.10 atm/s

E. 2.6 x 10–3 atm/s ------------------------------------------------------------------------------------------------------------------------------- 5. For the following nuclear reaction, what is the value of x?

15 A. 1 B. 3 C. 5 D. 7 E. 9 ------------------------------------------------------------------------------------------------------------------------------- 6. Given the initial rate data shown in the table below, what is the rate law of the following reaction?

Experiment [A] (M) [B] (M) Initial Rate (M/s)

1 0.1 0.2 1.2 x 10−4

2 0.1 0.4 4.8 x 10−4

3 0.2 0.2 1.2 x 10−4

A. Rate = k[A][B]2

B. Rate = k[A]2[B]

C. Rate = k[A]2

D. Rate = k[B]2

E. Rate = k[B]

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

------------------------------------------------------------------------------------------------------------------------------- 7. Which points on the reaction profile below represent intermediates?

A. C and E only

B. B, D and F only

C. A and G only

D. B, C, D, E and F only

E. D only ------------------------------------------------------------------------------------------------------------------------------- 8. Consider the reaction below: Br2 (aq) + HCOOH (aq) → 2 Br− (aq) + 2 H+ (aq) + CO2 (g) Why does the instantaneous reaction rate for this chemical reaction decrease with time? (Assume temperature is constant.) A. The activation energy increases.

B. CO2 gas is escaping into the atmosphere.

C. The concentration of Br2 decreases.

D. The HCOOH is a catalyst.

E. ΔE for the reaction increases. -------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------- 9. What type of particle or radiation is emitted when a F-20 nucleus decays to Ne-20? A. alpha

B. beta

C. neutron

D. positron

E. proton ------------------------------------------------------------------------------------------------------------------------------- 10. The first-order reaction A → B in which A molecules (black circles) are converted to B molecules (white circles) in a 2.0 L container is shown below at two points in time. What is the concentration of A molecules after 40 seconds?

A. 8.0 molecules/L

B. 4.0 molecules/L

C. 2.0 molecules/L

D. 12 molecules/L

E. 6.0 molecules/L -------------------------------------------------------------------------------------------------------------------------------

t = 0 s t = 20 s

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 11. A reaction has the following rate law:

Rate = k[A][B]2

In experiment 1, the concentrations of A and B are both 0.10 M. In experiment 2, the concentrations of A

and B are both 0.30 M. If the temperature stays constant, what is the value of the ratio ?

A. 3.0

B. 6.0

C. 9.0

D. 18

E. 27 ------------------------------------------------------------------------------------------------------------------------------- 12. What does a catalyst do? A. It lowers the overall enthalpy of the reaction.

B. It lowers the activation energy of the forward reaction only.

C. It raises the activation energy of the reverse reaction only.

D. It lowers the activation energy of both the forward and reverse reactions.

E. It raises the energy of the reactant molecules. -------------------------------------------------------------------------------------------------------------- 13. Why does the rate of a reaction increase with increasing temperature? A. The reactant molecules collide less frequently.

B. The reactant molecules collide with greater energy.

C. The activation energy is lowered.

D. The reactant molecules collide with the right orientation.

E. The concentration of the reactant molecules increases. -------------------------------------------------------------------------------------------------------------------------------

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 14. What is the nuclear binding energy per nucleon, in joules, for a 25Mg nucleus? (nuclear mass 24.985839 amu) [Use the following data: proton (mass) = 1.007825 amu; neutron (mass) = 1.008665 amu] A. 0.22076 J/nucleon

B. 3.25 x 10–11 J/nucleon

C. 1.32 x 10–12 J/nucleon

D. 0.999 J/nucleon

E. 2.64 x 10–12 J/nucleon ------------------------------------------------------------------------------------------------------------------------------- 15. Iodine-131, t1/2 = 8.0 days, is used in the diagnosis and treatment of thyroid gland diseases. If a laboratory sample of iodine-131 initially emits 9.95 x 1018 β particles per day, how long will it take for the activity to drop to 6.22 x 1017 β particles per day? A. 2.0 days

B. 16 days

C. 32 days

D. 128 days

E. 64 days -------------------------------------------------------------------------------------------------------------------------------

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 16. The decomposition of NO2 was studied at 656 K and the data was plotted below: The y-intercept of the plot is 9.20 M−1, and the slope of the line is 10.16 M−1sec−1. For a different experiment at the same temperature and an initial NO2 concentration of 0.200 M, how long would it take to decompose half of the NO2? A. 15.1 sec

B. 5.62 sec

C. 1.39 sec

D. 0.492 sec

E. 0.068 sec ------------------------------------------------------------------------------------------------------------------------------- 17. The only stable isotope of aluminum is 27Al. What type of radioactive decay would 23Al be expected to undergo? A. proton emission

B. neutron emission

C. beta decay

D. positron emission

E. alpha decay -------------------------------------------------------------------------------------------------------------------------------

(M−

1 )

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 18. The temperature dependence of the rate constant for a second order reaction is plotted below:

The y-intercept of the plot is 23.2, and the slope of the line is −1.61 x 104 K. Based on this data, what would the rate constant be at 500 K? A. 1.23 x 10−4 M-1 s−1

B. 2.95 x 10−2 M-1 s−1

C. 3.49 x 10−1 M-1 s−1

D. 4.77 M−1 s−1

E. 5.11 x 103 M−1 s−1 ------------------------------------------------------------------------------------------------------------------------------- 19. Potassium-40 undergoes positron emission to form argon-40 with a half-life of 1.2 x 109 years. If a sample of rock from an asteroid contains 82% argon with the remaining portion being potassium, what is the age of the rock? (Assume that all of the argon in the sample is the result of potassium decay.) A. 3.4 x 108 years

B. 2.1 x 109 years

C. 8.3 x 108 years

D. 1.5 x 106 years

E. 3.0 x 109 years -------------------------------------------------------------------------------------------------------------------------------

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 20. What is the balanced nuclear equation represented by the following diagram?

A.

B.

C.

D.

E.

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

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 21. For the overall reaction 2 N2O5 (g) → 4 NO2 (g) + O2 (g) the following mechanism is proposed:

N2O5 (g) NO2 (g) + NO3 (g) (fast equilibrium)

NO2 (g) + NO3 (g) → NO2 (g) + NO (g) + O2 (g) (slow)

NO3 (g) + NO (g) → 2 NO2 (g) (fast)

Which statement is true about the rate law that is consistent with this mechanism? A. The rate law is first order in N2O5.

B. The rate law is second order in NO2 and first order in NO3.

C. The rate law is first order in NO2 and NO3 and second order in N2O5.

D. The rate law is second order in N2O5.

E. None of these choices is consistent with the rate law. ------------------------------------------------------------------------------------------------------------------------------- 22. The isomerization of methyl isocyanide, CH3NC → CH3CN, follows first-order kinetics. The half-lives were found to be 161 min at 199°C and 12.5 min at 230°C. What is the activation energy for this reaction? A. 6.17 x 10–3 kJ/mol

B. 31.4 kJ/mol

C. 78.2 kJ/mol

D. 124 kJ/mol

E. 163 kJ/mol -------------------------------------------------------------------------------------------------------------------------------

Go on to the next page

------------------------------------------------------------------------------------------------------------------------------- 23. Suppose a certain biologically important reaction is quite slow at physiological temperature (37oC) in the absence of a catalyst. Assuming that the collision factor A remains the same, by how much must an enzyme lower the activation energy of the reaction to achieve a million-fold increase (1 x 106) in the reaction rate? A. 10 kJ/mol

B. 36 kJ/mol

C. 51 kJ/mol

D. 74 kJ/mol

E. 82 kJ/mol ------------------------------------------------------------------------------------------------------------------------------- 24. The rate constant k for the reaction 3A → 4B is 6.00 x 10–3 M–1min–1. How long will it take for the concentration of A to drop from 0.75 M to 0.25 M? A. 2.2 x 10–3 min

B. 5.5 x 10–3 min

C. 180 min

D. 440 min

E. 5.0 x 102 min -------------------------------------------------------------------------------------------------------------------------------

Go on to the last page 

------------------------------------------------------------------------------------------------------------------------------- 25. During a medical PET scan a patient is injected with a tracing compound that contains an 18F isotope, which decays through positron emission. When the emitted positron encounters an electron both are completely destroyed through a matter-antimatter reaction, producing two photons that propagate in opposite directions. If the energy of each photon is 8.187 x 10–14 J, what is the mass of the positron? A. 2.174 x 10−4 amu

B. 5.483 x 10−4 amu

C. 2.097 x 10−3 amu

D. 1.0072765 amu

E. 1.0086649 amu ------------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------

END OF TEST

CHEM 112

SPRING 2013 EXAM 1

FORM - A SCRAP PAPER

CHEM 112

SPRING 2013 EXAM 1

FORM - A SCRAP PAPER

Chem 112 Data Sheet 1. Standard Electrode Potentials Half-reaction Eo

1/2(V) F2(g) + 2e– 2F–(aq) +2.87 H2O2(aq) + 2H+(aq) + 2e 2H2O() +1.78 Cl2(g) + 2e– 2Cl–(aq) +1.36 O2(g) + 4H+(aq) + 4e– 2H2O() +1.23 Br2() + 2e– 2Br–(aq) +1.07 Ag+(aq) + e– Ag(s) +0.80 Fe3+(aq) + e– Fe2+(aq) +0.77 O2(g) + 2H+(aq) + 2e– H2O2(aq) +0.68 I2(s) + 2e– 2I–(aq) +0.54 Cu+(aq) + e– Cu(s) +0.52 Cu2+(aq) + 2e– Cu(s) +0.34 Sn4+(aq) + 2e Sn2+(aq) +0.15 Cu2+(aq) + e– Cu+(aq) +0.15 2H+(aq) + 2e H2(g) –0.00 Pb2+(aq) + 2e Pb(s) –0.13 Sn2+(aq) + 2e Sn(s) –0.14 Co+2(aq) + 2e Co(s) 0.28 Ni2+(aq) + 2e– Ni(s) –0.28 Cd2+(aq) + 2e– Cd(s) –0.40 Fe2+(aq) + 2e– Fe(s) –0.44 Cr3+(aq) + 3e– Cr(s) –0.74 Zn2+(aq) + 2e– Zn(s) –0.76 2H2O() + 2e H2(g) + 2OH−(aq) –0.83 SO4

2−(aq) + H2O() + 2e− SO32−(aq) + 2OH−(aq) 0.93

Mn2+(aq) + 2e– Mn(s) –1.18 Al3+(aq) + 3e– Al(s) –1.66 Mg2+(aq) + 2e– Mg(s) –2.37 Na+(aq) + e– Na(s) –2.71 Ca2+(aq) + 2e– Ca(s) –2.76 Li+(aq) + e– Li(s) –3.05

2. Constants R = 8.314 J mol–1K–1

R = 0.0821 L-atm mol–1K–1

F = 96,500 coulombs/mol electrons

h = 6.62606876 x 10–34 J-s

mass 10n = 1.0086649 amu

mass 11p = 1.0072765 amu

1 g = 6.02 x 1023 amu 1 amp = 1 coul sec–1

Avogadro’s no. = 6.02214 x 1023 mol–1 c = 2.99792458 x 108m sec–1

1 J = 2

2

sec

mkg = C-V

3. Equations ∆G = ∆H – T∆S = – nFE ∆Go = –2.303 RT log K = –RT ln K ∆G = ∆Go + RT ln Q ∆G = ∆Go + 2.303 RT log Q

Eo = 0.0592

nlog K (at 25oC)

E = Eo – 0.0592

nlog Q (at 25oC)

pH = pKa + log ][

][

HX

X

Ka x Kb = Kw = [H+] [OH–] pKw = pH + pOH = pKa + pKb

Kp = Kc (RT)Δn Kw = 1 x 10–14 at 25°C

4. MO Theory E Diagrams

ln k = RT

Ea + ln A

ln 2

1

k

k =

R

Ea

12

11

TT

k = Ae(– RTa

)

ln[A] = ln[A]o –kt

ktA][

1

A][

1

o

t1/2 = 0.693/k t1/2 = 1/k[A]o

log o

t

N

N =

2

1

301.0

t

t =

303.2

kt Rate = kN E = mc2

ln o

t

N

N =

2

1

693.0

t

t = –kt k =

2

1

693.0

t

6. Crystal Field Splitting for octahedral complexes

E = hν

c = λν

Nam

e _______________________

eMail_______________________

Δo

dx2‐y2, dz2

dxy, dyz, dxz

E

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]