2010 U.S.NATIONAL CHEMISTRY OLYMPIAD LOCAL SECTION EXAM Prepared by the American Chemical Society Chemistry Olympiad Examinations Task Force OLYMPIAD EXAMINATIONS TASK FORCE Arden P. Zipp, Chair, State University of New York, Cortland, NY James Ayers, Mesa State College, Grand Junction, CO Sherry Berman-Robinson, Consolidated HS, Orlando Park, IL (retired) Seth Brown, University of Notre Dame, Notre Dame, IN Peter Demmin, Amherst HS, Amherst, NY (retired) Marian Dewane, Centennial HS, Boise, ID Xu Duan, Queen Anne School, Upper Marlboro, MD Valerie Ferguson, Moore HS, Moore, OK Julie Furstenau, Thomas B. Doherty HS, Colorado Springs, CO Kimberly Gardner, United States Air Force Academy, CO Regis Goode, Ridge View High School, Columbia, SC Paul Groves, South Pasadena HS, South Pasadena, CA Preston Hayes, Glenbrook South HS, Glenbrook, IL (retired) David Hostage, Taft School, Watertown, CT Dennis Kliza, Kincaid School, Houston, TX Adele Mouakad, St. John's School, San Juan, PR Jane Nagurney, Scranton Preparatory School, Scranton, PA Ronald Ragsdale, University of Utah, Salt Lake City, UT DIRECTIONS TO THE EXAMINER This test is designed to be taken with an answer sheet on which the student records his or her responses. All answers are to be marked on that sheet, not written in the booklet. Each student should be provided with an answer sheet and scratch paper, both of which must be turned in with the test booklet at the end of the examination. Local Sections may use an answer sheet of their own choice. The full examination consists of 60 multiple-choice questions representing a fairly wide range of difficulty. Students should be permitted to use non-programmable calculators. A periodic table and other useful information are provided on page two of this exam booklet for student reference. Suggested Time: 60 questions—110 minutes DIRECTIONS TO THE EXAMINEE DO NOT TURN THE PAGE UNTIL DIRECTED TO DO SO. This is a multiple-choice examination with four choices for each question. There is only one correct or best answer to each question. When you select your choice, blacken the corresponding space on the answer sheet with your pencil. Make a heavy full mark, but no stray marks. If you decide to change your answer, be certain to erase your original answer completely. Distributed by American Chemical Society, 1155 16th Street, N.W., Washington, DC 20036 All rights reserved. Printed in U.S.A. Property of ACS USNCO -Not for use as an USNCO Local Exam after March 31, 2010 4 62 Sm 94 Pu 152.31 12 Mg 20 Ca 38 Sr 39.626 × 10–34 J·s c = 2. K measure of pressure mmHg time milli– prefix m volt molal m volume CONSTANTS M M mol h P k Q s c T t V V R = 8.81 13 3A 5 B 13 Al 12.003 18 8A 2 He 10 Ne 18 Ar 20.93 9 8B 27 Co 10 8B 28 Ni 46 Pd 78 Pt 58.0821 L·atm·mol–1·K–1 1 F = 96.1 44 Ru 76 Os 102.9 183.61 32 Ge 50 Sn 74.0 63 Eu 157.7 121.3 132.0 93 Np (237) 95 Am (243) 96 Cm (247) 97 Bk (247) 100 Fm (257) 101 Md (258) 102 No (259) 103 Lr (262) (244) (251) (252) Page 2 Property of ACS USNCO Not for use as an USNCO Local Exam after March 31.94 42 Mo 74 W 101.22 92.3 64 Gd 158.09 30.62 88.9 45 Rh 77 Ir 106.10 40.00 16 6A 8 O 16 S 19.4 107.4 207.99 11 Na 19 K 24.9 67 Ho 99 Es 167.0 71 Lu 232.3 68 Er 168.55 11 1B 29 Cu 47 Ag 65.9 57 La 178.94 55.6 52 Te 126.4 48 Cd 114.8 186.39 12 2B 30 Zn 26.72 31 Ga 49 In 81 Tl 72.8 51 Sb 83 Bi 127.9 112.96 47.80 36 Kr 54 Xe 85.2 195.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 free energy G molar mass frequency ν mole gas constant R Planck’s constant gram g pressure hour h rate constant joule J reaction quotient kelvin K second kilo– prefix k speed of light liter L temperature.9 65 Tb 162.500 C·mol–1 1 F = 96.2 60 Nd 92 U 61 Pm (145) 150.008 1 1A 1 H 3 Li PERIODIC TABLE OF THE ELEMENTS 2 2A 4 Be 3 3B 21 Sc 39 Y 4 4B 22 Ti 40 Zr 5 5B 23 V 6 6B 24 Cr 7 7B 25 Mn 43 Tc (98) 6.0 91 Pa 238.2 75 Re 190.500 J·V–1·mol–1 NA = 6.012 10.5 66 Dy 98 Cf 164.1 58 Ce 140.9 137.85 8 8B 26 Fe 58.998 × 108 m·s–1 0 °C = 273.00 54.0 84 Po (209) 85 At (210) 86 Rn (222) 88 Ra (226) 89 Ac (227) 104 Rf (261) 105 Db (262) 106 Sg (266) 107 Bh (264) 108 Hs (277) 109 Mt (268) 110 Ds (281) 111 Rg (272) 112 (277) 113 (Uut) 114 (Uuq) 115 (Uup) 116 (Uuh) 117 (Uus) 118 (Uuo) (223) 140.15 K 1.96 34 Se 79.8 118.0 90 Th 231.0 70 Yb 175.2 192.47 37 Rb 55 Cs 87 Fr 87.97 15 P 32.91 41 Nb 73 Ta 95.9 59 Pr 144.45 39.2 82 Pb 209.022 × 1023 mol–1 h = 6.92 33 As 78.95 69.91 91.00 17 7A 9 F 17 Cl 4.01 15 5A 7 N 16.18 22.98 28.3 56 Ba 138.01 14 4A 6 C 14 Si 14.90 35 Br 53 I 83. 2010 .941 9.08 44.94 52.0 79 Au 200.69 63.6 80 Hg Uub 204.5 72 Hf 180.9 131.9 69 Tm 173.1 197.07 35.88 50.314 J·mol–1·K–1 R = 0. Any questions for which more than one response has been blackened will not be counted. The formula obtained experimentally was CuSO4 •5.512 kg (D) 7. blacken the corresponding space on the answer sheet using a soft. but no stray marks.5 kg of glucose? (A) 0.4 mL (B) 30.96 kg (B) 0. Which error best accounts for the difference in results? (A) During heating some of the hydrated copper(II) sulfate was lost. A student performed an experiment to determine the ratio of H2O to CuSO4 in a sample of hydrated copper(II) sulfate by heating it to drive off the water and weighing the solid before and after heating.20 M NaCl (B) 0.20 M NaOH (C) 0. The best explanation for this behavior is that camphor is a(n) (A) ionic solid (C) molecular solid (B) metallic solid (D) network solid 10. Magnesium chloride dissolves in water to form (A) hydrated MgCl2 molecules (B) hydrated Mg2+ ions and hydrated Cl– ions (C) hydrated Mg2+ ions and hydrated Cl22– ions (D) hydrated Mg atoms and hydrated Cl2 molecules 11. The result was a green flame.0 g? (A) 23. When phenolphthalein is added to an aqueous solution containing one of the following solutes the solution turns pink.0) (C) N2O3 (M = 76.9 mL 6. Enzymes convert glucose (M= 180.93 kg 5. (B) The hydrated sample was not heated long enough to drive off all the water. #2 pencil.0 g of methanol (d = 0. What is the coefficient for O2 when the following reaction __As2S3 + __O2 → __ As2O3 + __SO2 is correctly balanced with the smallest integer coefficients? (A) 5 (B) 6 (C) 8 (D) 9 2. If you decide to change an answer. Mg2+. Property of ACS USNCO – Not for use as an USNCO Local Exam after March 31. 2010 Page 3 . full mark. Make a heavy.256 kg (C) 3.7 mL (C) 32.7914 g/mL at 25˚C) but has only a graduated cylinder with which to measure it. 1. Which solute is present? (A) NaCl (C) LiBr (B) KC2H3O2 (D) NH4NO3 9. erase the unwanted mark completely.2) to ethanol (M= 46.DIRECTIONS When you have selected your answer to each question.6 × 1023 (D) 8. Which reagent should be used to selectively precipitate the Ag+? (A) 0.1) according to the equation C6H12O6 → 2C2H5OH + 2CO2 What is the maximum mass of ethanol that can be made from 15.5 × 1022 (C) 4. Which compound contains the highest percentage of nitrogen by mass? (A) NH2OH (M = 33. A student is asked to measure 30.1) 3.5 × 1023 (B) 3. An aqueous solution is known to contain Ag+.0) (B) NH4NO2 (M = 64. (D) The student used a balance that gave weights that were consistently too high by 0. It is to your advantage to answer every question. There is only one correct answer to each question.1 × 1023 4.025 mol of the isotope 54 Cr ? 24 (A) 1. (C) The student weighed out too much sample initially. What volume of methanol should the student use to obtain the required 30.20 M Na3PO4 7. How many neutrons are in 0. A flame test was performed to confirm the identity of a metal ion in solution. and Sr2+ ions.20 M Na2SO4 (D) 0. Which of the following metal ions is indicated? (A) copper (C) strontium (B) sodium (D) zinc 8.10 g.5H2O but the accepted formula is CuSO4 •5H2O. Solid camphor is insoluble in water but is soluble in vegetable oil.0 mL (D) 37. Your score is based solely on the number of questions you answer correctly.1) (D) NH4NH2CO2 (M = 78. Which process is exothermic? (A) condensation (C) sublimation (B) fusion (D) vaporization 13. ∆S is positive Page 4 Property of ACS USNCO Not for use as an USNCO Local Exam after March 31. What is the molarity of acetic acid in vinegar? [density of vinegar = 1.4 kJ ∆Hf˚ kJ/mol –825. 2010 .2 15.833 M (C) 1. (B) H2O has a higher boiling point than N2 or O2. Moist air is less dense than dry air at the same temperature and barometric pressure.8 kJ (C) –52.06 L (D) 2.8 kJ/mol 2NO2(g) → N2O4(g) ∆H˚ = –58. The critical temperature of water is the (A) temperature at which solid.00 L balloon at 20.2 kJ (D) –77.20 L 14.6 (D) 171. (B) temperature at which water vapor condenses.12. Which family of elements has solid.0 kJ/mol to calculate ∆H˚ in kJ/mol for the reaction: 2NO(g) + O2(g) → N2O4(g) (A) –171. What is the new volume of the balloon? (A) 0.0˚C and 745 mmHg floats to an altitude where the temperature is 10. A 2.0). Which reaction has the most positive entropy change under standard conditions? (A) H2O(g) + CO(g) → H2(g) + CO2(g) (B) CaCO3(s) → CaO(s) + CO2(g) (C) NH3(g) → NH3(aq) (D) C8H18(l) → C8H18(s) 23.4 kJ/mol ½ N2(g) + O2(g) → NO2(g) ∆H˚ = 33.00% by mass aqueous solution of acetic acid. ∆S is negative (A) A → B (B) A → C (C) B → C (D) C → B (C) ∆H is negative. ∆S is positive (B) ∆H is positive.0˚C and the air pressure is 700 mmHg. CH3CO2H (M = 60.06 L (C) 2.4 (B) –26. liquid and gaseous members at 25˚C and 1 atm pressure? (A) alkali metals (Li – Cs) (C) chalcogens (O – Te) (B) pnictogens (N – Bi) (D) halogens (F – I) 20. (C) H2O has a lower molar mass than N2 or O2.94 L (B) 1.20 M (B) 1. What are the signs of ∆H and ∆S for a reaction that is spontaneous only at low temperatures? (A) ∆H is positive. Under certain conditions CO2 melts rather than sublimes. (D) H2O has a higher heat capacity than N2 or O2.00 g of Fe2O3 with aluminum metal according to the equation Fe2O3(s) + 2Al(s) → Al2O3(s) + 2Fe(l) Substance Fe2O3(s) Al2O3(s) Fe(l) (A) –25.00 g/mL] (A) 0. Determine the enthalpy change for the reaction of 5.5 –1675.00 M 18. liquid and gaseous water coexist. Commercial vinegar is a 5. (D) minimum temperature at which water vapor can exist. This gas could be (A) He (M = 4) (C) C7H12 (M = 96) (B) C2H5F (M = 48) (D) C5F12 (M = 288) 16. ∆S is negative (D) ∆H is negative. Which is the best explanation for this observation? (A) H2O is a polar molecule but N2 and O2 are not.9 kJ 22.6 (C) 114.00 M (D) 3. To which transition in the phase diagram does this change correspond? 21.2 (B) –114. Use the thermodynamic information: ½ N2(g) + ½O2(g) → NO(g) ∆H˚ = 90. (C) maximum temperature at which liquid water can exist. A gas diffuses one-third as fast as O2 at 100 ˚C. 17. 19.7 12. Kc. In which reaction at equilibrium will the amount of reactants present increase with an increase in the container volume? (A) C(s) + CO2(g) (B) H2(g) + F2(g) (C) CO(g) + NO2(g) (D) N2(g) + 3 H2(g) 2CO(g) 2 HF(g) CO2(g) + NO(g) 2NH3(g) 33. The reaction C3H7I + Cl → C3H7Cl + I is thought to occur in the polar solvent CH3OH by the mechanism: Step 1 C3H7I → C3H7+ + I (slow) Step 2 C3H7+ + Cl → C3H7 Cl (fast) Which species is an intermediate in this reaction? (A) CH3OH (B) C3H7+ (C) I– (D) Cl– 30. Consider the following reactions: X(NO3)2 + Y → X + Y(NO3)2 X(NO3)2 + Z → X + Z(NO3)2 Y(NO3)2 + Z → No reaction What is the correct order of increasing activity for the metals. The first-order disappearance of a substance has a halflife of 34.7% (C) 1.24. For the cell E˚ = 0.27 g (C) 102 s – (D) 272 s 29. M Time (sec) – – – 37. mL of 0. kJ/mol (D) 240.3% 27.0400 0.8 ×10–4] (A) 4. What is the equilibrium expression.8 × 10–3 mol/min (D) 8.20 M in HF and 0. The times listed are those recorded at 25˚C for the reaction below to produce a measurable amount of I2(aq): S2O82–(aq) + 2I (aq) → I2(aq) + 2SO42–(aq) Experiment Initial [S2O82–].0100 0.0 × 10 5] (A) 0. (C) size of the solid particles. How long does it take for the concentration of that substance to fall to 12. kJ/mol (B) 100.0 × 10–4 mol/min 32. what is the rate of appearance of NH3(g)? (A) 2. (B) volume of the container.04 (B) 2.92 (B) 2.0200 0.20 g (B) 0.2 × 10–3 mol/min.0013 g (C) 0.107 M HCl. A reaction is endothermic with ∆H = 100. kJ/mol. Y.5% of its initial value? (A) 11 s (B) 68 s – 36.0200 39 78 156 ? 38. kJ/mol (C) 140. If the activation enthalpy of the forward reaction is 140.0400 0. If the rate of disappearance of H2(g) is 1. what is the activation enthalpy of the reverse reaction? (A) 40. (D) Increasing the pressure of the H2(g).40 M in NaF? [Ka = 7.14 (D) 3.2 × 10–4] (A) 1. mL by evaporation. (D) temperature. mL saturated solution of MgCO3 (M = 84) is reduced to 120. (B) Increasing the [Zn2+].76 V Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g) Which change will increase the voltage of the cell? (A) Increasing the size of the Zn electrode. M Initial – [I ]. What mass of solid – MgCO3 is formed? [Ksp = 4. mL of H2O? (A) 3. What is the percentage ionization of HCOOH molecules in a 0. X. kJ/mol.2% (B) 2. kJ/mol 35. 140. 26.43 (D) 2. Factors that can affect the rate of a chemical reaction between a solid and a solution include all of the following EXCEPT the (A) concentration of the reactants in solution. 2010 . Z? (A) X < Y < Z (C) Z < Y < X (B) X < Z < Y (D) Z < X < Y 1 2 3 4 0.4 × 10–3 mol/min (C) 1.0800 0.44 28.8% (D) 1. A 500.0 s. What is the pH of a solution that is 0.84 (C) 3.0800 0. and 160. Page 5 What is the expected time for experiment 4? (A) 156 sec (B) 234 sec (C) 312 sec (D) 624 sec Property of ACS USNCO – Not for use as an USNCO Local Exam after March 31.27 34.0400 0. What is the pH of a solution made by mixing 200.10 M solution? [Ka = 1.2 × 10–3 mol/min (B) 1.74 (C) 2. The commercial production of ammonia is represented by the equation N2(g) + 3H2(g) → 2NH3(g).0657 M NaOH.064 g (D) 0. Which substance has a non-zero standard free energy of formation? (A) Pb(s) (B) Hg(l) (C) Cl2(g) (D) O3(g) 31. (C) Increasing the [H+]. mL of 0. for the reaction: 2SO3(g)? 2S(s) + 3O2(g) (A) Kc = 2[SO3]/(2[S]+3[O2]) (C) Kc = [SO3] /[S] [O2] 2 2 3 (B) Kc = 2[SO3]/3[O2] (D) Kc = [SO3]2/[O2]3 25. 44. 2010 .66V (C) 1. are best described as being (A) all 120˚ (C) all 90˚ (B) all 109. How many unpaired electrons are in a gaseous Co3+ ion in its ground state? (A) 0 (B) 2 (C) 4 (D) 6 40. Which ionic solid has the greatest lattice energy? (A) NaCl (B) MgO (C) KBr (D) SrS 55. (D) Green light has a higher frequency than blue light. (B) electron.0A is passed through a solution of copper(II) nitrate for 30. SO52–? (A) 32 (B) 34 (C) 36 (D) 38 (B) ClO3 (aq) and Cl (aq) (D) Cl (aq) and H (aq) E˚ = 0. Which statement concerning visible light is correct? (A) The product of wavelength and frequency is a constant for visible light in a vacuum. (C) neutron.5˚ (D) two 90˚. Ernest Rutherford’s scattering experiment demonstrated the existence of the (A) alpha particle. one 180˚ 42. and CH4 are listed in order of increasing boiling point.403g (D) 6. (C) As the wavelength of light increases its amplitude also increases. What is the IUPAC name for the molecule below? 45. which order is correct? (A) CH4 < NH3 < H2O < HF (B) NH3 < CH4 < H2O < HF (C) HF < CH4 < H2O < NH3 (D) CH4 < NH3 < HF < H2O 54. The O–N–O bond angles in the nitrate ion. Which diatomic molecule contains the strongest bond? (A) H–Cl (B) H–F (C) Cl–Cl (D) F–F Co (aq) + 2e → Co(s) E˚ = –0. (D) nucleus.88V – 51. ____ electron(s) is (are) _____. (B) As the wavelength of light increases the energy of a photon increases.28 V Use the standard reduction potentials to determine the standard potential for the reaction: Co(s) + 2Ag+(aq) → Co2+(aq) + 2Ag(s) (A) 0.04g 52. (A) Cl (aq) and ClO3 (aq) (C) ClO3 (aq) and H (aq) 41. For which pair of species is the difference in radii the greatest? (A) Li and F (C) Li+ and O2– (B) Li+ and F– (D) O2– and F– 56. The removal of an electron from which gaseous atom requires the greatest amount of energy? (A) Na (B) Cl (C) K (D) Br (A) heptane (C) 3-methylhexane (B) 2-ethylpentane (D) 4-ethylpentane 46. How many valence electrons are in a persulfate ion.39. How many different aldehydes have the formula C5H10O? (A) 2 (B) 3 (C) 4 (D) 5 Page 6 Property of ACS USNCO Not for use as an USNCO Local Exam after March 31. When the compounds HF.08V (D) 1. respectively. H2O. Ag+(aq) + e–→ Ag(s) 2+ – + – – 48.6 seconds? (A) 0. (A) 3 gained (C) 1 lost (B) 1 gained (D) 3 lost – 47. What mass of copper is deposited when a current of 10. Which element has the greatest electrical conductivity? (A) As (B) Ge (C) P (D) Sn 49. NO3–.52V (B) 0. NH3. The electron configuration of cobalt (Z = 27) is 1s22s22p63s23p63d74s2. 53. Which molecule has no permanent dipole moment? (A) BCl3 (B) NCl3 (C) CHCl3 (D) PCl3 43.80 V – + – – 50.101g (B) 0. In the reaction – – ClO3 (aq) + 5Cl (aq) + 6H+(aq) → 3Cl2(g) + 3H2O(l) the oxidizing and reducing agents are. When the half-reaction NO3 → NO is balanced for one – NO3 in acid solution.201g (C) 0. Which element is used to form cross-links between the strands of latex rubber? (A) Fe (B) N (C) P (D) S 60. END OF TEST Property of ACS USNCO -Not for use as an USNCO Local Exam after March 31. (D) it is of animal origin. Which compound will rapidly decolorize bromine in CHCl3? (A) benzene (C) hexane (B) cyclohexane (D) 1-hexene 58. The classification of a fat as saturated or unsaturated is based on whether (A) it can be metabolized by humans. 2010 .57. (B) it contains carbon – carbon double bonds. (C) it has twenty or more carbon atoms. Which combination of reactants produces an ester? (A) acid and alcohol (C) alcohol and aldehyde (B) acid and aldehyde (D) aldehyde and potassium permanganate 59. 17. 48. 53. 14. 15. 51. 42. 5. 3. 27. 47. 43. 18. 8. 36.S. 35. 10. 40. 20. 34.2010 U. 46. 60. 37. 2. 29. 11. 4. 24. 52. 44. 16. 57. Answer D D C A D C B C A B C A A D B C C D D B A A D B C C D A D B Not for use as a USNCO Local Section Exam after March 31. 56. 22. 6. 19. 58. 49. 2010 . 38. 30. 23. 54. Answer D A B C A A D B C B D A C D D C A C A A A B C D B D A C B C Number 31. 26. 39. 55. 50. 33. 32. 21. 9. 28. 41. 45. 59. 7. National Chemistry Olympiad Local Section Exam KEY Number 1. 13. 12. 25.