2008 Academic Challenge

Transcription

1 2008 Academic Challenge CHEMISTRY TEST - REGIONAL - - This Test Consists of 40 Questions - - Chemistry Test Production Team Don DeCoste, University of Illinois at Urbana - Champaign Author/Team Leader Gretchen Adams, University of Illinois at Urbana - Champaign Author Nancy Carter Dopke, Alma College Reviewer Don Wayman, WYSE Coordinator of Test Production GENERAL DIRECTIONS Please read the following instructions carefully. This is a timed test; any instructions from the test supervisor should be followed promptly. The test supervisor will give instructions for filling in any necessary information on the answer sheet. Most Academic Challenge sites will ask you to indicate your answer to each question by marking an oval that corresponds to the correct answer for that question. Only one oval should be marked to answer each question. Multiple ovals will automatically be graded as an incorrect answer. Be sure ovals are marked as. Not as,,, etc. If you wish to change an answer, erase your first mark completely before marking your new choice. You are advised to use your time effectively and to work as rapidly as you can without losing accuracy. Do not waste your time on questions that seem too difficult for you. Go on to the other questions, and then come back to the difficult ones later if time remains. *** TIME: 40 MINUTES *** DO NOT OPEN TEST BOOKLET UNTIL YOU ARE TOLD TO DO SO! 2008 Worldwide Youth in Science and Engineering WYSE, Worldwide Youth in Science and Engineering and the WYSE Design are service marks of and this work is Copyright 2008 by the Board of Trustees of the University of Illinois at Urbana - Champaign. All rights reserved.

2 Periodic Table of the Elements *Lanthanides **Actinides 1A 2A 3A 4A 5A 6A 7A 8A 19 K Ca Rb Sr Cs Ba Li Be Na Mg H Fr (223) 88 Ra Sc Ti V Cr Mn Fe Co Ni Cu Zn Y Zr Nb Mo Tc (98) 44 Ru Rh Pd Ag Cd La* Hf Ta W Re Os Ir Pt Au Hg Unq 105 Unp 106 Unh 107 Uns 108 Uno 109 Une 89 Ac** (227) 31 Ga In Tl B Al Ge Sn Pb C Si As Sb Bi N P Se Te Po (209) 8 O S Br I At (210) 9 F Cl He Kr Xe Rn (222) 10 Ne Ar Ce Pr Nd Pm (145) 62 Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa (231) 92 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 (260)

3 The information on this page may be useful in completing this exam. ph = -log[h + ] poh = -log[oh - ] K w = 1 x PV = nrt (R = L atm mol -1 K -1 ) (R = J mol -1 K -1 ) K = C ΔG = ΔH TΔS N A = x atoms mol -1 E = x J (Z 2 /n 2 ) Assume gases behave ideally unless specifically told otherwise. Assume solutions are aqueous and at 25 C unless specifically told otherwise. Simple Rules for the Solubility of Salts in Water 1. Most nitrate salts are soluble. 2. Most salts containing the alkali metal ions (Li +, Na +, K +, Cs +, Rb + ) and the ammonium ion (NH 4 + ) are soluble. 3. Most chloride, bromide, and iodide salts are soluble. Notable exceptions are salts containing the ions Ag +, Pb 2+, and Hg Most sulfate salts are soluble. Notable exceptions are BaSO 4, PbSO 4, Hg 2 SO 4, and CaSO Most hydroxide salts are only slightly soluble. The important soluble hydroxides are NaOH and KOH. The compounds Ba(OH) 2, Sr(OH) 2, and Ca(OH) 2 are marginally soluble. 6. Most sulfide, carbonate, chromate, and phosphate salts are only slightly soluble.

4 WYSE Academic Challenge Chemistry Test (Regional) Which of the following compounds is named incorrectly? a) KNO 3 potassium nitrate b) TiO 2 titanium(ii) oxide c) Sn(OH) 4 tin(iv) hydroxide d) PBr 5 phosphorus pentabromide e) CaCrO 4 calcium chromate 2. Which of the following diagrams best represents a mixture of a compound with a diatomic element? a) b) c) d) e) 3. At what temperature does 121 ml of CO 2 at 27 C and 1.05 atm occupy a volume of 293 ml at a pressure of 1.40 atm? a) 87 C b) 165 C c) 272 C d) 696 C e) 969 C

5 Chemistry 2 4. By how much would the pressure of a gas change if the Celsius temperature doubles and the volume of the container remains constant? a) The pressure of the gas would increase but not double since pressure is directly related to the Kelvin temperature of the gas. b) The pressure of the gas would decrease by half since pressure and temperature are inversely proportional at these conditions. c) The pressure of the gas would not change since pressure is not dependent on temperature. d) The pressure of the gas would not change since pressure is always equal to the atmospheric pressure outside the container. e) The pressure of the gas would also double since pressure and temperature are directly proportional at these conditions Use the following unbalanced equation to answer questions 5 and 6. MnO ( s) + Al( s) Mn( s ) + Al O ( ) s 5. If 5.00 moles of Mn(s) were produced, how many moles of Al(s) were required? a) 3.33 mol b) 3.75 mol c) 5.00 mol d) 6.67 mol e) none of these 6. If 2.00 moles of MnO 2 and 2.00 moles of Al are reacted, how many moles of Al 2 O 3 would be produced? a) 4.00 mol b) 3.00 mol c) 2.00 mol d) 1.33 mol e) 1.00 mol How many electrons are in the most stable ion formed by calcium in a compound? a) 18 b) 20 c) 22 d) 12 e) When electrons are shared equally between atoms in a molecule, we call this a(n) bond. a) covalent b) ionic c) polar d) hydrogen e) London dispersion 9. Which of the following elements has the largest first ionization energy? a) P b) Al c) Cl d) Ba e) K 10. Which of the following compounds has the highest boiling point? a) H 2 O b) MgCl 2 c) CO 2 d) CH 4 e) SF 4

6 Chemistry Consider the following equation CO(g) + H 2 O(g) CO 2 (g) + H 2 (g) Which of the following must be true at equilibrium? a) [CO 2 ] = [H 2 ] because they are in a 1:1 mole ratio in the balanced equation. b) The total concentration of reactants is equal to the total concentration of the products. c) The total concentration of the reactants is greater than the total concentration of the products. d) The total concentration of the products is greater than the total concentration of the reactants. e) None of these. 12. How many of the following four statements is/are true considering significant figures? I. For any mathematical operation performed on two measurements, the number of significant figures in the answer is the same as the least number of significant figures in either of the measurements. II has 8 significant figures. III has 5 significant figures. IV. The answer to [ ] has 1 significant figure. a) 0 b) 1 c) 2 d) 3 e) What is the molar mass of potassium carbonate? a) g/mol b) g/mol c) g/mol d) g/mol e) g/mol 14. Which of the following is the most accurate description of a mole? a) The number of particles in a 1.0 M solution. b) The mass of carbon in a measured sample of carbon. c) The number of sodium ions in g of sodium chloride. d) The number of atoms in any given mass of an element. e) The amount of an ideal gas measured at STP. 15. Which of the following statements is true concerning real gases? a) The observed pressure will be less than the ideal pressure, and the volume available for the gas particles is less than the volume of the container. b) The observed pressure will be greater than the ideal pressure, and the volume available for the gas particles is greater than the volume of the container. c) The observed pressure will be greater than the ideal pressure, and the volume available for the gas particles is less than the volume of the container. d) The observed pressure will be less than the ideal pressure, and the volume available for the gas particles is greater than the volume of the container. e) This question cannot be answered without knowing the identity of the gas.

7 Chemistry Which of the following combinations of quantum numbers is not allowed? n l m (l) m (s) a) /2 b) /2 c) /2 d) /2 e) /2 17. In 2001, scientists at Berkeley had to retract a claim that they had synthesized element 118. Recently (October 14, 2006), scientists in Dubna, Russia did synthesize Ununoctium (UUo), or element 118. What is the expected ground state electron configuration for element 118? a) [Rn] 7s 2 6d 10 7 p 2 b) [Rn] 7s 2 5f 14 6d 10 7 p 6 c) [Rn] 7s 2 6f 14 6d 10 7 p 2 d) [Rn] 7s 2 7d 10 7 p 2 e) [Rn] 7s 2 5f 14 7d 10 7 p How many resonance structures does the molecule SO 2 have? a) 0 b) 1 c) 2 d) 3 e) For questions 19-21, consider the reaction as represented by the unbalanced equation CaO(s) + C(s) CaC 2 (s) + CO 2 (g) Consider reacting 10.0 mol of CaO with 10.0 mol of C and answer the following questions. 19. Determine the number of moles of CaC 2 produced after the reaction is complete. a) 1.00 mol b) 2.00 mol c) 4.00 mol d) 5.00 mol e) 10.0 mol 20. Determine the number of moles of CO 2 produced after the reaction is complete. a) 1.00 mol b) 2.00 mol c) 4.00 mol d) 5.00 mol e) 10.0 mol 21. Determine the moles of reactant left over. a) 6.0 mol of CaO b) 2.0 mol of CaO c) 5.0 mol of C d) 10.0 mol of C e) none of these (a-d) What is the minimum volume of a 2.00 M NaOH (aq) solution needed to make ml of a M NaOH (aq) solution? a) 375 ml b) 150. ml c) 120. ml d) 90.0 ml e) 60.0 ml

8 Chemistry The electron configuration 1s 2 2s 2 2p 6 3s 2 3p 4 is the correct electron configuration for which element? a) O b) P c) Ar d) Se e) S 24. The energy barrier that must be overcome to produce a chemical reaction is referred to as a) potential energy. b) activation energy. c) kinetic energy. d) enthalpy. e) entropy. 25. For the atoms Li, N, F, and Na, which of the following is the correct order from smallest to largest atomic radius? a) Na, F, N, Li b) Na, Li, N, F c) Li, N, F, Na d) N, F, Na, Li e) F, N, Li, Na 26. A compressed gas cylinder, at 135 atm and 296K, is in a room where a fire occurs. The fire raises the temperature of the gas to 748K. What is the new pressure in the cylinder? a) 6.54 atm b) 53.4 atm c) 341 atm d) 2790 atm e) none of these 27. Determine the percent nitrogen by mass of NH 4 NO 3. a) 11.0% b) 17.5% c) 21.9% d) 35.0% e) 52.3% 28. When ml of water is added to ml of 1.00 M HCl, a) the ph decreases because the solution is diluted. b) the ph does not change because water is neutral. c) the ph is doubled because the volume is now doubled. d) the ph increases because the concentration of H + decreases. e) the solution is completely neutralized. 29. Which of the following does not involve a chemical change? a) Lighting a match. b) Leaves changing color in the fall. c) Sugar dissolving in water. d) Eating a cupcake. e) A fireworks display.

9 Chemistry How many significant figures are in the measurement grams? a) 3 b) 4 c) 5 d) 6 e) What is the concentration of a solution made by dissolving 50.0 g of sodium chloride in ml of solution? a) 3.90 M b) M c) 2.05 M d) 1.78 M e) 2.85 M 32. Two species are isotopes of one another if they have a) the same number of protons and neutrons but different numbers of electrons. b) the same number of protons and electrons but different numbers of neutrons. c) the same number of neutrons and electrons but different numbers of protons. d) different number of protons (the number of neutrons and the number of electrons do not matter). e) different number of electrons (the number of neutrons and the number of protons do not matter). 33. If the intermolecular forces for substance A are stronger than the intermolecular forces for substance B, a) the boiling point of substance A is higher than the boiling point for substance B. b) the vapor pressure of substance A is higher than the vapor pressure for substance B. c) the freezing point of substance A is lower than the freezing point of substance B. d) the viscosity of substance A is lower than the viscosity of substance B. e) More information is required to answer this question. 34. Weak acid HA is weaker than weak acid HB. From this we know a) the ph of a solution of HA is lower than the ph of a solution of HB (these solutions are of equal concentration). b) the conjugate base A - is weaker than the conjugate base B -. c) the ph of at least one of the solutions must be greater than d) the value of K a for HA is lower than the value of K a for HB. e) More information is required to answer this question. 35. Which of the following compounds contains the greatest percent hydrogen by mass? a) CH 4 b) H 2 O c) HCl d) C 3 H 8 e) H 2 O Which of the following is true when a metal reacts with a nonmetal? a) The metal is generally reduced and the nonmetal is generally oxidized. b) The oxidation state of the metal generally increases. c) Electrons are transferred from the nonmetal to the metal. d) The reaction is not a redox reaction. e) None of the above statements are true.

10 Chemistry What is the shape of the molecule NH 3? a) trigonal planar b) tetrahedral c) linear d) trigonal pyramid e) T-shape 38. What is the correct name of BaCl 2? a) barium(ii) chloride b) barium chloride c) barium dichloride d) barium chorite e) barium chlorate 39. When salt is dissolved in water a) the freezing point and boiling point both decrease. b) the freezing point and boiling point both increase. c) the freezing point decreases and the boiling point increases. d) the freezing point increases and the boiling point decreases. e) the direction of the changes in freezing point and boiling point cannot be predicted. 40. are characterized by the presence of the hydroxyl group (-OH). a) Aldehydes b) Ketones c) Esters d) Amines e) Alcohols