2015 U.S. NATIONAL CHEMISTRY OLYMPIAD

1 Property of ACS USNCO Not for use as USNCO Local Section Exam after March 31, 2015 Distributed by the american chemical society , 1155 16th Street, , Washington, DC 20036 All rights reserved. Printed in 2015 NATIONAL CHEMISTRY OLYMPIAD LOCAL SECTION EXAM Prepared by the american chemical society CHEMISTRY OLYMPIAD Examinations Task Force OLYMPIAD EXAMINATIONS TASK FORCE Seth N. Brown, Chair, University of Notre Dame, Notre Dame, IN James Ayers, Mesa State College, Grand Junction, CO Mark DeCamp, University of Michigan, Dearborn, MI (retired) Xu Duan, Holton-Arms School, Bethesda, MD Valerie Ferguson, Moore HS, Moore, OK Julie Furstenau, Thomas B.

2 Doherty HS, Colorado Springs, CO Kimberly Gardner, United States Air Force Academy, CO Paul Groves, South Pasadena HS, South Pasadena, CA David W. Hostage, Taft School, Watertown, CT Dennis Kliza, Kincaid School, Houston, TX John Kotz, State University of New York, Oneonta, NY (retired) 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 (retired) 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.

3 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. A periodic table and other useful information are provided on page two of this exam booklet for student reference. Only non-programmable calculators are to be used on the ACS local section exam. The use of a programmable calculator, cell phone, or any other device that can access the internet or make copies or photographs during the exam is grounds for disqualification.

4 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. Page 2 Property of ACS USNCO Not for use as USNCO Local Section Exam after March 31, 2015 ABBREVIATIONS AND SYMBOLS CONSTANTS amount of substance n ampere A atmosphere atm atomic mass unit u Avogadro constant NA Celsius temperature C centi prefix c coulomb C density d electromotive force E energy of activation Ea enthalpy H entropy S equilibrium constant K Faraday constant F free energy G frequency gas constant R gram g hour h joule J kelvin K kilo prefix k liter L measure of pressure mm Hg milli prefix m molal m molar M molar mass M mole mol Planck s constant h pressure P rate constant k reaction quotient Q second s speed of light c temperature.

5 K T time t vapor pressure VP volt V volume V R = J mol 1 K 1R = L atm mol 1 K 1F = 96,500 C mol 1F = 96,500 J V 1 mol 1NA = 1023 mol 1h = 10 34 J s c = 108 m s 1 0 C = K 1 atm = 760 mm Hg Specific heat capacity of H2O = J g 1 K 1 EQUATIONS olnRTEEQnF 1lnconstantHKRT 211211lnaEkkR TT 1 PERIODIC TABLE OF THE ELEMENTS181A8A 1 H 13 14 15 16 17 2A 3A 4A 5A 6A 7A 2 He Li Be B C N O F Ne Na Mg 3B 4 4B 5 5B 6 6B 7 7B 8 8B 9 8B 10 8B 11 1B 12 2B 13 Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc (98)

6 44 Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi 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 (263)107 Bh (262)108 Hs (265)109 Mt (266)110 Ds (281)111 Rg (272)112 Cn (285)113 (Uut)(284)114 Fl (289)115 (Uup)(288)116 Lv (293)117 (Uus)(294)118 (Uuo)(294)58 Ce Pr Nd Pm (145)62 Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U 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)o Property of ACS USNCO Not for use as USNCO Local Section Exam after March 31, 2015 Page 3 Page 3 DIRECTIONS When you have selected your answer to each question, blacken the corresponding space on the answer sheet using a soft, #2 pencil.

7 Make a heavy, full mark, but no stray marks. If you decide to change an answer, erase the unwanted mark very carefully. There is only one correct answer to each question. Any questions for which more than one response has been blackened will not be counted. Your score is based solely on the number of questions you answer correctly. It is to your advantage to answer every question. 1. Benzene, C6H6, reacts with oxygen, O2, to form CO2 and H2O. How much O2 is required for the complete combustion of mol C6H6? (A) mol (B) mol (C) mol (D) 12 mol 2. A g sample of a soluble barium salt is treated with an excess of sodium sulfate to precipitate g BaSO4 (M = ).

8 Which barium salt is it? (A) BaCl2 (M = ) (B) Ba(O2CH)2 (M = ) (C) Ba(NO3)2 (M = ) (D) BaBr2 (M = ) 3. What is the concentration of nitrate ion in a 425 mL solution containing g of Mg(NO3)2 (M = )? (A) M (B) M (C) M (D) M 4. The formula for terbium phosphate is TbPO4. The formula for terbium sulfate is (A) Tb2SO4 (B) TbSO4 (C) Tb2(SO4)3 (D) Tb(SO4)2 5. A mL sample of M silver nitrate, AgNO3, is reacted with a g sample of calcium chloride, CaCl2 (M = ). Which of the following statements is true? (A) Silver nitrate is the limiting reactant and calcium nitrate precipitates. (B) Silver nitrate is the limiting reactant and silver chloride precipitates.

9 (C) Calcium chloride is the limiting reactant and calcium nitrate precipitates. (D) Calcium chloride is the limiting reactant and silver chloride precipitates. 6. Which aqueous solution exhibits the largest freezing point depression? (A) m KBr (B) m C6H12O6 (C) m MgCl2 (D) m Ga2(SO4)3 7. Which calcium compound is not appreciably more soluble in M hydrochloric acid than it is in pure water? (A) Limestone, CaCO3 (B) Slaked lime, Ca(OH)2 (C) Gypsum, CaSO4 2 H2O (D) Hydroxyapatite, Ca5(OH)(PO4)3 8. Which metal reacts most vigorously with water at 25 C? (A) Na (B) Mg (C) K (D) Ca 9. Each of the following forms a colored aqueous solution EXCEPT (A) Cr(NO3)3 (B) Co(NO3)2 (C) Cu(NO3)2 (D) Zn(NO3)2 10.

10 A student wishes to measure 37 mL of a liquid. Which apparatus would be most suitable? (A) 50 mL graduated cylinder (B) 50 mL volumetric pipet (C) 50 mL beaker (D) 50 mL Erlenmeyer flask 11. A mL sample of a colorless solution, when treated with a few drops of 2 M hydrochloric acid, forms a white precipitate which dissolves when the solution is heated to boiling. The original solution could have contained which of the following cations? I. M Ag+ II. M Pb2+ (A) I only (B) II only (C) Either I or II (D) Neither I nor II 12. Which compound has the lowest normal boiling point? (A) HF (B) HCl (C) HBr (D) HI 13. Which of the following would lead to an increase in the vapor pressure of a liquid?