# 2014美国奥林匹亚化学试题1

NATIONAL EXAM PART I

Arden P. Zipp, Chair, State University of New York, Cortland, NY (deceased)
James Ayers, Mesa State College, Grand Junction, CO Mark DeCamp, University of Michigan, Dearborn, MI Marian DeWane, Centennial HS, Boise, ID Xu Duan, Holton-Arms School, Bethesda, MD Valerie Ferguson, Moore HS, Moore, OK Julie Furstenau, Thomas B. Doherty HS, Colorado Springs, CO Kimberly Gardner, United States Air Force Academy, CO Paul Groves, South Pasadena HS, South Pasadena, CA Preston Hayes, Glenbrook South HS, Glenbrook, IL (retired) Adele Mouakad, St. John's School, San Juan, PR (retired) Jane Nagurney, Scranton Preparatory School, Scranton, PA Ronald Ragsdale, University of Utah, Salt Lake City, UT

Property of ACS USNCO – Not for use as USNCO National Exam after April 28, 2014 Distributed by the American Chemical Society, 1155 16 th Street, N.W., Washington, DC 20036 All rights reserved. Printed in U.S.A.

amount of substance ampere atmosphere atomic mass unit Avogadro constant Celsius temperature centi– prefix coulomb density electromotive force energy of activation enthalpy entropy equilibrium constant

n A atm u NA °C c C d E Ea H S K

ABBREVIATIONS AND SYMBOLS Faraday constant F molar mass free energy G mole frequency ? Planck’s constant gas constant R pressure gram g rate constant hour h reaction quotient joule J second kelvin K speed of light kilo– prefix k temperature, K liter L time measure of pressure mm Hg vapor pressure milli– prefix m volt molal m volume molar M

CONSTANTS M mol h P k Q s c T t VP V V R = 8.314 J?mol 1?K 1 – – R = 0.0821 L?atm?mol 1?K 1 – 1 F = 96,500 C?mol 1 – –1 1 F = 96,500 J?V ?mol 1 – NA = 6.022 × 1023 mol 1 h = 6.626 × 10–34 J?s c = 2.998 × 108 m?s–1 0 °C = 273.15 K 1 atm = 760 mm Hg
– –

EQUATIONS

E ? Eo ?

RT ln Q nF

? ??H ?? 1 ? ln K ? ? ?? ? ? constant ? R ?? T ?

?k ? E ? 1 1 ? ln ? 2 ? ? a ? ? ? ? k1 ? R ? T1 T2 ?

1 1A 1 H
1.008

PERIODIC TABLE OF THE ELEMENTS
2 2A 4 Be
9.012

3 Li
6.941

13 3A 5 B
10.81

14 4A 6 C
12.01

15 5A 7 N
14.01

16 6A 8 O
16.00

17 7A 9 F
19.00

18 8A 2 He
4.003

10 Ne
20.18

11 Na
22.99

12 Mg
24.31

19 K
39.10

20 Ca
40.08

3 3B 21 Sc
44.96

4 4B 22 Ti
47.88

5 5B 23 V
50.94

6 6B 24 Cr
52.00

7 7B 25 Mn
54.94

8 8B 26 Fe
55.85

9 8B 27 Co
58.93

10 8B 28 Ni
58.69

11 1B 29 Cu
63.55

12 2B 30 Zn
65.39

13 Al
26.98

14 Si
28.09

15 P
30.97

16 S
32.07

17 Cl
35.45

18 Ar
39.95

31 Ga
69.72

32 Ge
72.61

33 As
74.92

34 Se
78.96

35 Br
79.90

36 Kr
83.80

37 Rb
85.47

38 Sr
87.62

39 Y
88.91

40 Zr
91.22

41 Nb
92.91

42 Mo
95.94

43 Tc
(98)

44 Ru
101.1

45 Rh
102.9

46 Pd
106.4

47 Ag
107.9

48 Cd
112.4

49 In
114.8

50 Sn
118.7

51 Sb
121.8

52 Te
127.6

53 I
126.9

54 Xe
131.3

55 Cs
132.9

56 Ba
137.3

57 La
138.9

72 Hf
178.5

73 Ta
180.9

74 W
183.8

75 Re
186.2

76 Os
190.2

77 Ir
192.2

78 Pt
195.1

79 Au
197.0

80 Hg
200.6

81 Tl
204.4

82 Pb
207.2

83 Bi
209.0

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
(271)

107 Bh
(270)

108 Hs
(277)

109 Mt
(276)

110 Ds
(281)

111 Rg
(280)

112 Cn
(285)

113
(Uut) (284)

114 Fl
(289)

115
(Uup) (288)

116 Lv
(293)

117
(Uus) (294)

118
(Uuo) (294)

58 Ce
140.1

59 Pr
140.9

60 Nd
144.2

61 Pm
(145)

62 Sm
150.4

63 Eu
152.0

64 Gd
157.3

65 Tb
158.9

66 Dy
162.5

67 Ho
164.9

68 Er
167.3

69 Tm
168.9

70 Yb
173.0

71 Lu
175.0

90 Th
232.0

91 Pa
231.0

92 U
238.0

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)

Page 2

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2. A compound with 69.41% C, 4.16% H and 26.42% O has – a molar mass of 230 – 250 g?mol 1. What is its molecular formula? (A) C13H9O4 (C) C13H6O4 (B) C14H10O4 (D) C15H14O3

3. Aluminum reacts with sulfur to form aluminum sulfide. If 31.9 g of Al are reacted with 72.2 g of S, what is the theoretical yield of aluminum sulfide in grams? (A) 88.8 g (B) 69.7 g (C) 57.2 g (D) 113 g

10. According to the Tyndall effect, a beam of light becomes visible when passed through all of the following except a(n) (A) aerosol. (C) emulsion. (B) colloid. (D) solution.

4. According to EPA guidelines the permissible level for lead in drinking water is 15 parts per billion (ppb). What is the maximum allowable mass of lead that could be present in 1.00 L of H2O? (A) 0.015 ng (C) 0.015 mg (B) 0.015 ?g (D) 0.015 g

11. All of the following can be used as primary standards in acid-base titrations EXCEPT (A) oxalic acid. (B) potassium hydrogen phthalate. (C) sodium carbonate. (D) sodium hydroxide. 12. Which of the graphs shown below would best represent the changes when 0.10 M barium hydroxide was titrated with 0.10 M sulfuric acid? (A) (B)

5. Aqueous solutions of electrolytes that produce two ions upon ionization typically exhibit freezing point depressions that are twice as large as solutions of nonelectrolytes with the same concentration. Which 0.10 M electrolyte solution will show the smallest depression? (A) HCl (B) NaBr (C) KNO3 (D) MgSO4

6. Interferon is a water-soluble protein. A solution prepared by dissolving 15.0 mg of interferon in 2.50 mL of H 2O exhibits an osmotic pressure of 5.80 mm Hg at 25 °C. What is the molar mass of interferon? (A) 1.92 × 104 g?mol (C) 1.95 × 106 g?mol
–1

(B) 1.92 × 107 g?mol

–1 –1

–1

(D) 1.61 × 103 g?mol

(C)

(D)

7. Which noble gas is most abundant in the earth's atmosphere? (A) He (B) Ne (C) Ar (D) Rn

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Page 3

13. Which physical property decreases with an increase in intermolecular molecular forces? (A) boiling point (B) enthalpy of vaporization (C) vapor pressure (D) viscosity 14. A 0.180 g sample of liquid H2O is injected into a 5.00 L flask at 25 °C. What will be present in the flask when equilibrium is established? (Vapor pressure H2O at 25 °C = 23.8 mm Hg) (A) H2O vapor at a pressure of 186 mm Hg (B) H2O vapor at a pressure of 37.2 mm Hg (C) liquid H2O and H2O vapor at a pressure of 37.2 mm Hg (D) liquid H2O and H2O vapor at a pressure of 23.8 mm Hg 15. The atmospheric pressure on the summit of Mt. Everest is 0.333 atmospheres. At what temperature (in °C) does – H2O boil there? (?Hvap H2O = 40.7 kJ?mol 1) (A) 71 °C (B) 87 °C (C) 96 °C (D) 98 °C

19. The combustion of 2-propanol (M = 60.0 g?mol 1) occurs according to the equation, 2 CH3CHOHCH3(l) + 9 O2(g) ? 6 CO2(g) + 8 H2O(l) What is q for the combustion of 15.0 g of 2-propanol? ?Hf, kJ?mol
–1

CH3CHOHCH3(l) –318.2

CO2(g) –393.5

H2O(l) –285.8

(A) –5.01 × 102 kJ (C) –2.01 × 103 kJ

(B) –1.00 × 103 kJ (D) –4.01 × 103 kJ

20. At what temperature does the reaction below change from favoring products to favoring reactants? SO2(g) + ? O2(g) SO3(g) ?Hf°, kJ?mol 1 – S°, kJ?mol 1?K-1 (A) 162 K

SO2(g) –296.8 0.248

O2(g) 0.205

SO3(g) –395.7 0.257 (D) 1540 K

(B) 509 K

(C) 1060 K

21. Which isomer of C4H8 has the lowest absolute entropy at 25 °C? (A) 1-butene (C) trans-2-butene (B) cis-2-butene (D) cyclobutane

16. The arrangement of ions in a solid is best investigated by means of (A) infrared spectroscopy. (B) mass spectroscopy. (C) UV-visible spectroscopy. (D) x-ray crystallography. 17. Benzene and toluene form an ideal solution. The vapor pressure of benzene at 55 °C is 400 mm Hg while the vapor pressure of toluene at 55 °C is 130 mm Hg. What is the vapor pressure of a solution consisting of 0.5 mole fraction of benzene and 0.5 mole fraction of toluene at 55 °C? (A) lower than 130 mm Hg (B) between 130 and 400 mm Hg (C) exactly 400 mm Hg (D) greater than 400 mm Hg 18. An oxide of rhenium crystallizes with eight rhenium atoms at the corners of the unit cell and 12 oxygen atoms on the edges between them. What is the formula of this oxide? (A) ReO (B) Re2O3 (C) ReO2 (D) ReO3

22. A 10.0 g piece of gallium (M = 69.7) at 25.0 °C is placed in 10.0 g of H2O at 55.0 °C. What is the final temperature when this system comes to equilibrium? (Assume the specific heat capacity of liquid Ga is the same as that of solid Ga.) Cp, J?g 1?K Ga H2O (A) 35.0 °C (C) 41.8 °C 0.371 4.184
– –1

melting point °C 30.0

?Hfus, kJ?mol 5.576

–1

(B) 38.1 °C (D) 52.6 °C

23. In the Born-Haber calculation of the lattice enthalpy of LiF from its elements, which process is exothermic? (A) dissociation energy of F2(g) (B) electron affinity of F(g) (C) ionization energy of Li(g) (D) sublimation energy of Li(s) 24. How much work is done by the gas when 1.00 g of sodium – azide, NaN3 (M = 65.01 g?mol 1), decomposes in a container of changeable volume (e.g. an airbag in a car) against a constant pressure of 1.00 atm at 298 K? 2 NaN3(s) ? 2 Na(s) + 3 N2(g) (A) +114 J (B) +57.2 J (C) –114 J (D) –57.2 J

Page 4

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25. When the kinetics of the reaction, 2 A + 2 B ? C, were studied using the method of initial rates, the data in the table below were obtained. Initial Rate of – Trial [A]0 in mol?L 1 [B]0 in Formation of C – – – mol?L 1 in mol?L 1?s 1 – 1 0.060 0.040 3.6 × 10 4 – 2 0.060 0.080 7.2 × 10 4 – 3 0.030 0.12 5.4 × 10 4 What is the rate law for the reaction? (A) Rate = k[A][B] (C) Rate = k[A][B]2 26. (B) Rate = k[A]2[B] (D) Rate = k[A]2[B]2

30. For the reaction, 2 A + B ? C + D, the rate law is rate = k[B]. Which of the following mechanisms would be consistent with this information? (A) A + B ? M (slow) (B) A + A ? M (fast) A + M ? C + D (fast) (C) B ? M M+A?N (slow) (fast) B + M ? C + D (slow) (D) B ? M M+A?N (fast) (slow)

N + A ? C + D (fast)

N + A ? C + D (fast)

2 NO2(g) ? 2 NO(g) + O2(g) For the reaction above, a straight line for which plot indicates a second order reaction? (A) [NO2] vs. time (C) 1/[NO2] vs. time (B) [NO2] vs. time (D) 1/[NO2]2 vs. time
2

31. A 50.0 mL sample of a 1.00 M solution of a diprotic acid – – H2A (Ka1 = 1.0 × 10 6 and Ka2 = 1.0 × 10 10) is titrated with 2.00 M NaOH. What is the minimum volume of 2.00 M NaOH needed to reach a pH of 10.00? (A) 12.5 mL (C) 25.0 mL (B) 37.5 mL (D) 50.0 mL

27. What are the units for the rate constant of a zero-order reaction? (A) time (C) M?time (B) time
–1 –1

2 OF2(g), Kp = 41.0. 32. For the reaction, O2(g) + 2 F2(g) If PO2(g) = 0.116 atm and PF2(g) = 0.0461 atm at equilibrium, what is the pressure of OF2(g)? (A) 0.101 atm (C) 0.760 atm (B) 0.132 atm (D) 166 atm

(D) M?time

28. From the energy profiles for the two unimolecular reactions below, how will the rates of the two reactions compare if the temperature of each reaction is increased from 25 °C to 75 °C?

H2(g) + I2(g), what is the 33. For the reaction 2 HI(g) relationship between Kc and Kp at 25 °C? (A) Kc = Kp (B) Kc > Kp (C) Kc < Kp (D) The relationship varies depending on the pressure. 34. Calcium hydroxide is slightly soluble in water with a Ksp – of 1.3×10 6. What is the pH of a saturated solution of calcium hydroxide at 25 °C?

(A) The rate of reaction A ? B will increase more than the rate of reaction C ? D. (B) The rate of reaction C ? D will increase more than the rate of reaction A ? B. (C) The rates of the two reactions will increase by the same amount. (D) The rate of reaction A ? B will increase but the rate of reaction C ? D will decrease. 29. The half-life of a first-order reaction is 1.5 hours. How much time is needed for 94% of the reactant to change to product? (A) 0.13 hours (C) 2.3 hours (B) 6.1 hours (D) 36 hours

(A) 12.34

(B) 12.14

(C) 12.04

(D) 11.84

35. For the reaction, ADP + phosphate ? ATP, – ?G° = 30.50 kJ?mol 1. What is the value of the equilibrium constant, K, for this process under physiological conditions of 37.5 °C? (A) 4.5 × 10
–6

(B) 7.4 × 10

–6

(C) 1.3 × 105

(D) 2.2 × 105

36. When 0.0030 mol of HCl is added to 100. mL of a 0.10 M solution of a weak base, R2NH, the solution has a pH of 11.10. What is Kb for the weak base? (A) 2.9 × 10 (C) 4.1 × 10
–3 –5

(B) 5.4 × 10 (D) 1.6 × 10

–4 –5

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Page 5

37. Based on the reactions and data below, which reaction is least spontaneous? Reduction E° (V) 2 Hg2+ + 2 e– ? Hg22+ 1.82 I 2 + 2 e– ? 2 I – 0.53 2 H2O + 2 e– ? H2 + 2 OH– –0.83 (A) 2 Hg2+ + 2 I– ? Hg22+ + I2 (B) H2 + 2 OH– + I2 ? 2 H2O + 2 I– (C) 2 H2O + Hg2 ? H2 + 2 OH + 2 Hg (D) H2 + 2 OH + 2 Hg ? 2 H2O + Hg2
– 2+ 2+ – 2+ 2+

44. For the transition metal with the electron configuration 1s22s22p63s23p64s23d6, how many unpaired electrons are present in its +2 ion in the ground state? (A) 0 (B) 2 (C) 4 (D) 6
–28

45. What is the velocity of an electron (m = 9.11 × 10 that exhibits a de Broglie wavelength of 10.0 nm? [1 J = 1 kg?m2?s–2] (A) 72.7 m?s–1 (C) 7.27 × 104 m?s–1 (B) 270 m?s–1

g)

(D) 7.27 × 106 m?s–1

46. Which atom has the highest first ionization energy? (A) Al (B) Si (C) P (D) S

38. An increase in pH will promote which of the reactions below? I. 2 MnO4– + MnO2 + 4 OH– ? 3 MnO42– + 2 H2O II. 6 Cl2 + 2 I– + 6 H2O ? 12 Cl– + 2 IO3– + 12 H+ (A) I only (C) Both I and II (B) II only (D) Neither I nor II

47. What are the two most common oxidation states for antimony? (A) –1 and –3 (C) +3 and –3 (B) –1 and +2 (D) +3 and +5

39. Given the reactions and data below, what is the K value for this electrochemical cell? Cu|CuNO3(1.0 M)|| I–(1.0 M),I2(1.0 M)|Pt at 25 °C Reaction E° (V) Cu+ + e– ? Cu 0.518 I2 + 2 e– ? 2 I – 0.534 (A) 0.288 (B) 1.86 (C) 2.23 (D) 3.48

48. For which pair of species are the radii most similar? (A) Li and Na (C) Mn and Fe (B) Na and Mg (D) Fe2+ and Fe3+

49. When arranged in order of increasing bond strength, which order is correct? (A) O–O < S–S < O=O < S=S (B) O–O < S–S < S=S < O=O (C) S–S < O–O < O=O < S=S (D) S–S < O–O < S=S < O=O 50. Molecules with a permanent dipole moment include which of the following? I. HCN II. O3 III. XeF2 (A) I only (C) II and III only (B) I and II only (D) I, II, and III

40. The advantages of methane fuel cells over internal combustion engines (ICEs) that burn methane include which of the following? I. Methane fuel cells are less polluting. II. Methane fuel cells are more efficient. III. Methane fuel cells are less expensive. (A) I only (C) I and III only (B) I and II only (D) II and III only

41. A steady current of 1.20 Ampere is passed through a solution of MClx for 2 hours and 33 minutes. If 2.98 g of metal M are plated out, what is the identity of the metal? (A) Al (B) Cr (C) Ni (D) Zn

51. How many stable resonance forms can be written for the oxalate ion, C2O42–? (A) two (B) three

42. MnO4– + 5 Fe2+ + 8 H+ ? Mn2+ + 5 Fe3+ + 4 H2O E° = 0.743 V What is the value of E for the cell based on the reaction above at 25 °C for the following conditions? [MnO4–] 2.3×10–2 M (A) 0.20 V [Fe2+] 1×10–4 M (B) 0.45 V [Mn2+] 1.0 M [Fe3+] 1.0 M pH 3.00

(C) four

(D) five

52. What is the geometry of ICl4 according to VSEPR theory? (A) see-saw (C) tetrahedral (B) square planar (D) T-shaped

(C) 0.64 V

(D) 1.28 V

43. How many angular nodes does a d orbital possess? (A) 1 (B) 2 (C) 3 (D) 4

53. According to the molecular orbital theory, what is the bond order of the He–H bond? (A) ? (B) ? (C) 1 (D) 1 ?

Page 6

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54. As two atoms approach one another in space, the potential energy decreases then increases as shown in the diagram below.

59. Which of the compounds below can exist as a pair of enantiomers?

I. (A) I only (C) Both I and II To what are these two changes attributed? [NOTE: p+ = proton, e– = electron] decrease (from 0.40 to 0.15 nm) increase (from 0.15 to 0 nm)

II. (B) II only (D) Neither I nor II

60. Which type of dietary fat is the least healthy for humans? (A) cis-monounsaturated fat (B) polyunsaturated fat (C) saturated fat (D) trans-monounsaturated fat

(A) increased p+ e– attraction increased p+ p+ repulsion (B) increased p+ e– attraction increased e– e– repulsion (C) decreased p+ p+ repulsion increased e– e– repulsion (D) decreased p+ e– repulsion increased p+ p+ repulsion 55. Mild oxidation of 1-propanol, CH3CH2CH2OH, leads to the formation of (A) propanal, CH3CH2CHO. (B) propanoic acid, CH3CH2COOH. (C) 2-propanone, CH3COCH3. (D) dipropyl ether, CH3CH2CH2OCH2CH2CH3. 56. Which is the principal cation within cellular fluid? (A) Na+ (B) K+ (C) Mg2+ (D) Ca2+

END OF TEST
When you have finished answering this examination or time has been called by the Examiner, please provide responses to the following 4 items. Your answers will not affect your score on the exam but will help with a study being conducted by the U.S. National Chemistry Olympiad (USNCO) Subcommittee. 61. The amount of time I spend doing experiments in the laboratory per week on average during my chemistry course was/is? (A) less than ? hour (B) between ? and 1 hour (C) between 1 and 2 hours (D) more than 2 hours The following questions should be answered using the scale (A) Strongly agree (B) Agree (C) Disagree (D) Strongly disagree 62. As a result of my participation in the USNCO program, I plan to study more chemistry. 63. As a result of my participation in the USNCO program, I plan to major in chemistry in college. 64. As a result of my participation in the USNCO program, I have a more positive view of chemistry than I did before participating.

57. The shape of a chain segment of polypeptide chains in a protein is known as its (A) primary structure. (C) tertiary structure. (B) secondary structure. (D) quaternary structure.

58. Which property that polyacetylene exhibits is unusual for an organic polymer? (A) electrical conductivity (B) flexibility (C) high boiling point (D) strength

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Page 7

AMERICAN CHEMICAL SOCIETY

Olympiad 2014 USNCO National Exam Part I KEY

Number 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.

Answer D B A C D A C A C D D C C D A D B D A C D A B B A C D C B C

Number 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60.

Answer B A A B B B C C D B B A B C C C D C B B C B A A A B B A B D

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