2005 Academic Challenge

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1 2005 Academic Challenge CHEMISTRY TEST - STATE FINALS Chemistry Test Production Team Don DeCoste, University of Illinois at Urbana - Champaign Author/Team Coordinator Gretchen Adams, University of Illinois at Urbana - Champaign Author Alan Bruha, Lewis and Clark Community 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. Be sure you understand and correctly follow these instructions. You are 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. Test Question - 1. Which of the following was formed by the New Madrid Earthquakes of ? a. Lake of the Ozarks (MO) b. Little Grassy Lake (IL) c. Kentucky Lake (KY) d. Reelfoot Lake (TN) e. Crater Lake (OR) Answer Sheet - 1. A B C E 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 are too difficult for you. Go on to the other questions and come back to the difficult ones later if you can. *** TIME: 40 MINUTES *** DO NOT OPEN TEST BOOKLET UNTIL YOU ARE TOLD TO DO SO! 2005 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 2005 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 Useful Information 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 + 273?G =?H T?S N A = x atoms mol -1 E = x J (Z 2 /n 2 ) T = K b m solute T = K f m solute K b (for water) = 0.51 C kg/mol K f (for water) = 1.86 C kg/mol Assume gases behave ideally unless specifically told otherwise. Assume solutions are aqueous and at 25 C unless specifically told otherwise. STANDARD REDUCTION POTENTIALS (298 K) ε (V) Cl 2 + 2e - 2Cl Br 2 + 2e - 2Br Ag + + e - Ag 0.80 I 2 + 2e - 2I Cu e - Cu H + + 2e - H Al e - Al Na + + e - Na K + + e - K 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 (State Finals) Which of the following solutions has the greatest number of nitrate ions in solution? a) 5.0 mol potassium nitrate dissolved in water b) 2.0 mol iron(iii) nitrate dissolved in water c) 6.0 mol sodium nitrate dissolved in water d) 4.0 mol magnesium nitrate dissolved in water e) At least two of the above (a-d) have an equally great number of nitrate ions in solution. 2. A single molecule of a particular compound has a mass of 4.65 x g. Which of the following could be this compound? a) ammonia (NH 3 ) b) carbon monoxide c) nitrogen dioxide d) sulfur trioxide e) water 3. You have a sample of gas at 25 C. At what temperature would the sample have twice the average kinetic energy? a) 50 C b) 298 C c) 323 C d) 596 C e) none of these 4. Given equal masses of each of the following, which contains the greatest mass of phosphorus? a) barium phosphate b) magnesium phosphide c) phosphorus pentachloride d) phosphorus tribromide e) sodium phosphate 5. The percent by mass of nitrogen is 46.7% for a species containing only nitrogen and oxygen. Which of the following could be this species? a) the nitrate ion b) nitrogen dioxide c) nitrogen monoxide d) dinitrogen monoxide e) None of the above are 46.7% nitrogen by mass. 6. Which of the following makes a M NaOH solution? a) Mix ml of M NaOH with ml of M NaOH. b) Take 10.0 ml of 2.00 M NaOH and add ml water. c) Take 8.00 g of NaOH and dissolve it in ml solution. d) Mixing the solution made in part a above with the solution made in part c. e) None of the above

5 Chemistry 2 7. You have 245 ml of a sugar solution at 1.20 M. The next day the sugar solution has a concentration of 1.30 M. How much water evaporated from the solution? a) 18.8 ml b) 26.4 ml c) 226 ml d) 265 ml e) This is an impossible problem. The concentration of the solution will never go up. 8. For metals that form a 2+ charge in an ionic compound, the general equation when the metal is added to hydrochloric acid is M(s) + 2HCl (aq) MCl 2 (aq) + H 2 (g) g of a metal is added to ml of 1.00 M HCl and the hydrogen gas is collected at 25 C and 1.00 atm. Which of the following metals will give rise to the smallest balloon? a) Ca b) Zn c) Mg d) The balloons will be the same size because HCl(aq) is the limiting reactant. e) The balloons will be the same size although HCl(aq) is not the limiting reactant L of a 4.00 M solution of lead(ii) nitrate is added to 3.00 L of a 5.00 M solution of sodium iodide and a solid is formed. Which of the following correctly labels the ion with the highest concentration after the reaction is complete, and the ion that is not in solution after the reaction (concentration is 0 M)? ion with highest concentration 0 M a) Na + I - b) - NO 3 Pb 2+ c) Pb 2+ - NO 3 d) Na + Pb 2+ e) - NO 3 I Consider 2 reactants, A and B. The molar mass of A is greater than the molar mass of B. You add equal masses of A and B together and let them react. Which of the following statements must be true? a) Reactant A must be limiting. b) Reactant B must be limiting. c) If the coefficient for B is greater than the coefficient of A in the balanced equation, then reactant B must be limiting. d) If the coefficient for A is greater than the coefficient of B in the balanced equation, then reactant A must be limiting. e) None of the above choices (a-d) must be true.

6 Chemistry Which of the following is true about an isoelectronic series? a) The most positively charged species has the largest atomic radius, and the most negatively charged species has the smallest atomic radius. b) The noble gas has the largest atomic radius, and the most negatively charged species has the smallest atomic radius. c) The noble gas has the largest atomic radius, and the most positively charged species has the smallest atomic radius. d) The most negatively charged species has the largest atomic radius, and the most positively charged species has the smallest atomic radius. e) All of the species in an isoelectronic series have the same atomic radius. 12. How many lone pairs of electrons are around the central atom in ClF 2 +? a) 0 b) 1 c) 2 d) 3 e) You are given a compound with the formula CaX 2, in which X is a non-metal. You are told that the non-metal ion has 10 electrons. What is the symbol of the non metal? a) Cl b) Ne c) O d) F e) none of these 14. The autoionization of water, as represented by the below equation, is known to be endothermic. Which of the following correctly states what occurs as the temperature of water is raised? H 2 O (l) + H 2 O (l) H 3 O + (aq) + OH - (aq) a) The ph of the water does not change, and the water remains neutral. b) The ph of the water decreases, and the water becomes more acidic. c) The ph of the water decreases, and the water remains neutral. d) The ph of the water increases, and the water becomes more acidic. e) The ph of the water increases and the water remains neutral. 15. Which of the following correctly labels the salts? HF (Ka = 7.2 x 10-4 ) NH 3 (Kb = 1.8 x 10-5 ) HCN (Ka = 6.2 x ) a) NaCN = acidic, NH 4 F = basic, KCN = neutral b) NaCN = acidic, NH 4 F = neutral, KCN = basic c) NaCN = basic, NH 4 F = basic, KCN= neutral d) NaCN = basic, NH 4 F = neutral, KCN = basic e) NaCN = basic, NH 4 F = acidic, KCN = basic

7 Chemistry Consider a solution made by mixing 2.0 mol of HCN (Ka = 6.2 x ) with 1.0 mol of HC 2 H 3 O 2 (Ka = 1.8 x 10-5 ) in 1.0 L of solution. Determine the ph of this solution. a) 2.37 b) 3.41 c) 4.45 d) 4.74 e) None of these 17. Which of the following mixtures would result in a buffered solution? a) Mixing ml of M HCl with ml of M NaOH. b) Mixing ml of M NH 3 (Kb = 1.8 x 10-5 ) with ml of M NaOH. c) Mixing ml of M HCl with ml of M NH 3 (Kb = 1.8 x 10-5 ). d) Mixing 50.0 ml of M HCl with ml of M NH 3 (Kb = 1.8 x 10-5 ). e) At least two of the above mixtures would result in a buffered solution. 18. Calculate the ratio of solubility of AgCl in 5.00 M NaBr solubility of AgCl in water a) 320 b) 3.13 x 10-3 c) 3.9 x 10 5 d) 1.00 e) None of these. K sp for AgCl = 1.6 x K sp for AgBr = 5.0 x Consider the reaction at equilibrium N 2 (g) + 3H 2 (g) 2NH 3 (g). Which of the following statements must be true? a) The concentration of all the reactants and products are equal. b) The concentrations of all the reactants and products remain constant with time. c) The concentrations of the reactants are higher than the initial amount (before equilibrium was reached). d) The concentration of the product is higher than the concentrations of the reactants. e) At least two of the above (a-d) must be true. 20. A first-order reaction is 42% complete at the end of 17 minutes. What is the value of the rate constant? a) 3.2 x 10-2 min -1 b) 5.1 x 10-2 min -1 c) 20. min -1 d) 31 min -1 e) None of these

8 Chemistry A certain metal fluoride crystallizes in such a way that the fluoride ions occupy simple cubic lattice sites, while the metal atoms occupy the body centers of half the cubes. Which of the following could be the metal ion? a) The calcium ion b) The sodium ion c) The iron(iii) ion d) The vanadium(iv) ion e) Any of the above ions could be the metal ion. 22. Which of the following best describes a spontaneous reaction? a) Exothermic reactions are always spontaneous. b) Reactions for which G is less than zero are always spontaneous. c) A reaction that exhibits a negative value of S cannot be spontaneous. d) A reaction that exhibits a positive value of S surr is always spontaneous. e) None of these 23. You add an excess of solid Fe(OH) 3 to water (K sp for Fe(OH) 3 = 6.3 x ). Calculate the concentration of Fe 3+ at equilibrium. a) 2.2 x b) 2.5 x c) 2.5 x d) 6.3 x e) None of these. 24. You have a solution of two volatile liquids, A and B (assume ideal behavior). Pure liquid A has a vapor pressure of torr and pure liquid B has a vapor pressure of torr at the temperature of the solution. The vapor at equilibrium above the solution has double the mole fraction of substance A as the solution does. What is the mole fraction of liquid A in the solution? a) b) c) d) e) The reaction 2H 2 O(g) 2H 2 (g) + O 2 (g) has a positive value of G. Which of the following statements must be true? a) The reaction is slow. b) The reaction will not occur. [When H 2 O(g) is introduced into a flask, no O 2 or H 2 will form even over a long period of time.] c) The reaction is exothermic. d) The equilibrium lies far to the right. e) None of these is true.

9 Chemistry The reaction Cr(s) + NO 3 - (aq) Cr 3+ (aq) + NO(g) takes place in acidic solution. What is the coefficient of H 2 O(l) in the balanced equation? a) 1 b) 2 c) 3 d) 4 e) Suppose you are given the percent by mass of the elements in a compound and you wish to determine the empirical formula. Which of the following is true? a) You must convert percent by mass to relative numbers of atoms. b) You must assume exactly g of the compound. c) You must divide all of the percent by mass numbers by the smallest percent by mass. d) You cannot solve for the empirical formula without the molar mass of the compound. e) At least two of the above (a-d) are true. 28. Which of the following names is a correct one? a) 3,4-dichloropentane b) 1,1-dimethyl-2,2-diethylbutane c) cis-1,3-dimethylpropane d) 2-bromo-1-chloro-4,4-diethyloctane e) At least two of the above are correct. 29. You have a certain mass of helium gas (He) in a rigid steel container. You add the same mass of neon gas (Ne) to this container. Which of the following best describes what happens? Assume the temperature is constant. a) The pressure in the container doubles. b) The pressure in the container increases but does not double. c) The pressure in the container more than doubles. d) The volume of the container doubles. e) The volume of the container more than doubles. 30. A concentration cell is constructed using two metal (M) electrodes with M 2+ concentrations of 0.10 M and 1.00 x 10-5 M in the two half-cells. Determine the reduction potential of M 2+ given that the potential of the cell at 25 C is V. a) 0 V b) V c) V d) V e) Cannot be determined with the information given 31. Which of the following has the smallest radius? a) O 2- b) Na + c) Ne d) F - e) Mg 2+

10 Chemistry Which of the following requires the least energy to remove an electron? a) K + b) Ca + c) Ar + d) Cl + e) S How many of the following four molecules can correctly be described as bent? O 3 H 2 O SO 2 OCl 2 a) 0 b) 1 c) 2 d) 3 e) You have two separate containers each filled with gas. The containers have the same volume and are at the same temperature. The gases also exert the same pressure. Which of the following statements is true? a) For conditions of P, V, and T to be the same, the gases must be identical. b) For conditions of P, V, and T to be the same, the gases can be different but the number of moles of gas must be the same. c) For conditions of P, V, and T to be the same, the gases can be different but the mass of gas in each balloon must be the same. d) For conditions of P, V, and T to be the same, the gases can be different but the gases must have the same molar mass. e) None of the above statements are true. 35. Calculate the density of neon gas (Ne) at 1.00 atm and 25.0 C. a) g/l b) 9.84 g/l c) 20.2 g/l d) 22.4 g/l e) None of these 36. Hydrogen bonds account for which of the following observations? a) Hydrogen naturally exists as a diatomic molecule. b) Hydrogen is easily combustible with oxygen. c) Water molecules are bent or V-shaped. d) Air is more dense than hydrogen gas. e) For its molar mass, water has a high boiling point. 37. PVC, a common polymer used to make pipes and toys, is the abbreviation for a) polyvinyl carbon b) polystyrene c) polyvinyl chloride d) phosphorus(v) chloride e) polyacrylonitrile 38. Which of the following electromagnetic waves has the highest frequency? a) X-rays (wavelength = 0.1 nm) b) ultraviolet (wavelength = 10 nm) c) red light (wavelength = 700 nm) d) microwaves (wavelength = 2 x 10 7 nm) e) At least two of the above (a-d) have an equally great frequency.

11 Chemistry Consider the reaction at 25 o C 2NO(g) + Cl 2 (g) 2NOCl(g). The pressures at equilibrium were found to be P NOCl = 1.0 atm, P NO = 4.5 x 10-2 atm, and P Cl2 = 2.6 x 10-1 atm. Calculate the value of K for this reaction. a) 8.5 x 10 1 b) 1.9 x 10 3 c) 5.3 x 10-4 d) 3.9 x 10 3 e) 4.6 x Which of the following statements is false? a) The atoms that make up a solid are in motion. b) Water begins to turn into a gas at 100 o C and continues to do so as the temperature slowly rises. c) The process by which vapor molecules reform a liquid is called condensation. d) The boiling point of a liquid can change as the atmospheric pressure changes. e) The reverse process of sublimation is deposition.