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AVOGADRO EXAM 2004 UNIVERSITY OF WATERLOO DEPARTMENT OF CHEMISTRY 20 MAY 2004 TIME: 75 MINUTES This exam is being written by several thousand students. Please be sure that you follow the instructions below. We'll send you a report on your performance. Top performers are eligible for a prize. 1. Print your name here: 2. Print your school name and city on your STUDENT 4. Print your name (last name, first name and optional RESPONSE sheet. middle initial) on the STUDENT RESPONSE sheet. Also fill in the corresponding circles below your 3. Select, and enter on the STUDENT RESPONSE printed name. sheet, one of the following CODE numbers: Code 1 Ontario, now studying grade 11 Chemistry in a nonsemestered school Code 2 Ontario, now studying grade 11 Chemistry in a semestered school Code 3 Ontario, grade 11 Chemistry already completed Code 5 Manitoba or Saskatchewan high school student Code 6 Québec high school student Code 8 Alberta or British Columbia high school student Code 9 New Brunswick, Newfoundland, Nova Scotia or Prince Edward Island high school student 5. Now answer the exam questions. Questions are not in order of difficulty. Indicate your choice on the STUDENT RESPONSE sheet by marking one letter beside the question number. • Mark only one answer for each question. • Questions are all of the same value. • There is a penalty (1/4 off) for each incorrect answer, but no penalty if you do not answer. 6. Take care that you make firm, black pencil marks, just filling the oval. Be careful that any erasures are complete—make the sheet white again. Code 10 Northwest Territories, Nunavut, or Yukon high school student Code 11 High school student outside Canada Code 12 Teacher 1 1A 1 H 1.008 3 Li 6.941 11 Na 22.99 19 K 39.10 37 Rb 85.47 55 Cs 132.9 87 Fr (223) 2 2A 4 Be 9.012 12 Mg 3 4 24.31 3B 4B 20 21 22 Ca Sc Ti 40.08 44.96 47.88 38 39 40 Sr Y Zr 87.62 88.91 91.22 56 (57-71) 72 Ba La-Lu Hf 137.3 178.5 88 (89-103) 104 Ra Ac-Lr Rf (226) 5 5B 23 V 50.94 41 Nb 92.91 73 Ta 180.9 105 Db 6 6B 24 Cr 52.00 42 Mo 95.94 74 W 183.9 106 Sg 7 7B 25 Mn 54.94 43 Tc (98) 75 Re 186.2 107 Bh 8 ← 26 Fe 55.85 44 Ru 101.1 76 Os 190.2 108 Hs 9 8B 27 Co 58.93 45 Rh 102.9 77 Ir 192.2 109 Mt 10 → 28 Ni 58.69 46 Pd 106.4 78 Pt 195.1 110 Uun 11 1B 29 Cu 63.55 47 Ag 107.9 79 Au 197.0 111 Uuu 12 2B 30 Zn 65.38 48 Cd 112.4 80 Hg 200.6 112 Uub 13 3A 5 B 10.81 13 Al 26.98 31 Ga 69.72 49 In 114.8 81 Tl 204.4 113 Uut 14 4A 6 C 12.01 14 Si 28.09 32 Ge 72.59 50 Sn 118.7 82 Pb 207.2 15 5A 7 N 14.01 15 P 30.97 33 As 74.92 51 Sb 121.8 83 Bi 209.0 16 6A 8 O 16.00 16 S 32.07 34 Se 78.96 52 Te 127.6 84 Po (209) 17 7A 9 F 19.00 17 Cl 35.45 35 Br 79.90 53 I 126.9 85 At (210) 18 8A 2 He 4.003 10 Ne 20.18 18 Ar 39.95 36 Kr 83.80 54 Xe 131.3 86 Rn (222) AVOGADRO EXAM 2004 - ANSWERS 1 How many neutrons, protons and electrons are there in one 25Mg+ ion? A 25 neutrons, 25 protons, 24 electrons - - 2- - 2- A X (g) + e → X (g) 12 neutrons, 13 protons, 12 electrons C 13 neutrons, 12 protons, 13 electrons B X(g) + 2e → X (g) *D 13 neutrons, 12 protons, 11 electrons C X D X(g) → X 25 neutrons, 12 protons, 11 electrons An element, Z, has only two isotopes, with relative masses of 80.01 and 83.02. A naturally occurring sample of this element has a relative mass of 81.82. What is the percentage abundance of the lighter isotope? 2+ (g) → X + *E X (g) 5 2+ → X 3+ (g) + e (g) + 2e 2+ - - (g) + e - What is the correct Lewis symbol for the oxygen atom? A O B O C O What is the correct burette reading? * D O 24 E O A 30% *B 40% 3 For which of the following processes is the energy change equal to the second ionization energy of X(g)? B E 2 4 C 50% D 60% E 70% A 24.4 mL B 24.52 mL 6 *C 24.47 mL D 25.52 mL E 24.5 mL Which ion of magnesium is stable in magnesium compounds? *A Mg2+ 25 B Mg4+ C Mg3+ D Mg+ E Mg - 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /2 7 A 3.2×10-23 g B 1.9×10-25 g C 5.2×10-26 g A iron ions *B calcium ions C sodium ions 2.7×10-26 g D chloride ions E fluoride ions Which of the following bonds has the least ionic character? *A H-C 9 Avogadro constant: NA = 6.022×1023 mol-1 *D 5.3×10-23 g E 8 11 Which one of the following is the major cause of hardness in natural groundwater? What is the mass of one oxygen molecule? B O-H C K-H D C-F E C-O 12 The reaction Electronegativity values H, C, O, F, K, Br, 2 Na(s) + O2(g) → Na2O2(s) 2.1 2.5 3.5 4.0 0.8 2.8 is an example of *A a synthesis reaction In what region of the periodic table are the least metallic elements found? A upper centre B lower centre *C upper right D lower left E upper left B a decomposition reaction C a single displacement reaction D a double displacement reaction E an addition reaction IUPAC defines an addition reaction as “a chemical reaction of two or more reacting molecular entities, resulting in a single reaction product containing all atoms of all components, with formation of two chemical bonds and a net reduction in bond multiplicity in at least one of the reactants.” An example of an addition reaction is the addition of HBr across the double bond of ethene. 13 When zinc metal is treated with dilute aqueous sulfuric acid, H2SO4(aq), the products are 10 What is the correct formula for bismuth (III) sulfide? A Bi3S B BiS3 C Bi3S2 *D Bi2S3 E A ZnSO4, O2 and H2O B Zn(OH)2 and SO3 C Zn(OH)2 and SO2 *D ZnSO4 and H2 BiS E ZnS, H2O and O2 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /3 14 What are the spectator ions in the reaction below? Pb(NO3)2(aq) + 2 KI(aq) → PbI2(s) + 2 KNO3(aq) - A Pb2+, NO3 and I B Pb2+ and I - E K+ and Pb2+ Pb 13.0% *B 25.9% - 2+ compound N2O5? A - *C K+ and NO3 D 17 What is the percentage, by mass, of nitrogen in the C 28.6% D 35.0% E 40.0% + and K 18 Which combination of solutions would produce a 15 Balance the equation below using the smallest whole precipitate upon mixing? number coefficients. Cr2O3 + KOH + O2 → K2CrO4 + H2O What is the coefficient of O2 when the equation is balanced? A 2 *B 3 C 4 D 6 E 8 A Na2SO4(aq) and (NH4)2S(aq) B NaNO3(aq) and MgBr2(aq) C Ag2SO4(aq) and KNO3(aq) *D CuSO4(aq) and BaCl2(aq) E (NH4)2CO3(aq) and KNO3(aq) 19 Consider the equation below. 16 A particular compound has the following mass composition. 32.4% Na 0.71% H 21.8% P 45.1% O What is the empirical formula of the compound? A NaH2PO3 B Na2HPO3 C Na2H3PO D NaH2PO4 *E Na2HPO4 2 NaOH + Cl2 → NaCl + NaClO + H2O What is the maximum mass of NaClO that can be obtained from a reaction mixture containing 50.0 grams of NaOH and 71 grams of Cl2? *A 46.5 g B 93.1 g C 74.5 g D 186 g E 121 g 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /4 20 If 1.0 L of 0.10 mol L−1 NaNO3(aq) and 1.0 L of 0.20 mol L−1 Mg(NO3)2(aq) are mixed, what are the final concentrations of Na+, Mg2+ and NO3 ? A - - [Na+] = 0.050 mol L 1, [Mg2+] = 0.10 mol L 1, [ NO3 ] = 0.20 mol L 1 - - *B [Na+] = 0.050 mol L 1, [Mg2+] = 0.10 mol L 1, [ NO3 ] = 0.25 mol L 1 C D E - *A ethyne, C2H2 B hydrazine, N2H4 C ethanol, C2H5OH D hydrogen fluoride, HF E water, H2O - [Na+] = 0.050 mol L 1, [Mg2+] = 0.20 mol L 1, [ NO3 ] = 0.20 mol L 1 + -1 2+ 24 When three moles of calcium hydroxide, Ca(OH)2, react completely with two moles of phosphoric acid, H3PO4, how many moles of water are produced? -1 [Na ] = 0.050 mol L , [Mg ] = 0.10 mol L , [ NO3 ] = 0.40 mol L 1 + -1 2+ -1 [Na ] = 0.10 mol L , [Mg ] = 0.10 mol L , [ NO3 ] = 0.40 mol L 1 21 Which one of the following substances in aqueous solution is a nonelectrolyte? A 23 Which of the following does not show any significant hydrogen bonding? A one B two C three D four *E six NH4Cl *B CH3OH C LiF D HNO3 E CO2 Note: CO2 produces carbonic acid (H2CO3) which ionizes in solution. 22 Which of the following is the poorest electrical conductor? A aqueous sulfuric acid B graphite *C solid anhydrous potassium nitrate D platinum E molten sodium bromide 25 What is the minimum volume of pure oxygen required to burn 10.0 L of pure propane, C3H8, completely to carbon dioxide and water? (Assume that the volumes of oxygen and propane are measured at the same pressure and temperature.) A 10.0 L B 20.0 L C 30.0 L D 40.0 L *E 50.0 L 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /5 26 What volume of 0.142 mol L−1 HCl(aq) is required to neutralize 40.0 mL of 0.0217 mol L−1 Ca(OH)2(aq)? 29 Which colour of light has the highest energy per photon? *A 12.2 mL A red B 6.11 mL B orange C 3.06 mL C yellow D 76.4 mL D green E 17.2 mL *E violet 27 A sample of gas occupies a volume of 27 L at 20oC and normal atmospheric pressure. What is the volume at 250oC if the pressure remains constant? A 340 L B 2.2 L 30 Consider a sample comprised of 1.00 moles of an ideal gas. Which graph correctly displays how the product of pressure and volume changes with temperature? PV 0oC ≡ 273 K *A 0 *C 48 L D 15 L E 32 L 0 T 0 T 0 T 0 T 0 T PV B 0 28 What volume of ozone, O3, will have nearly the same number of molecules as 1.00 L of O2 gas, if both volumes are measured at the same temperature and pressure? PV C 0 A 22.4 L ozone B 6.00 L ozone C 1.50 L ozone PV D *D 1.00 L ozone E 0 0.17 L ozone PV E 0 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /6 34 How many structural isomers of C4H8 are there? 31 What is the oxidation state of chlorine in Cl2O? A -2 B -1 C 0 two B three C four D five *E six *D +1 E A +2 35 Which of the following electron attachment processes is/are endothermic? 32 Use the bond dissociation enthalpies provided to calculate ∆H for the reaction below. 3 H2(g) + N2(g) → 2 NH3(g) What is ∆H for the reaction? A +122 kJ *B -83 kJ H-H H-N N−N N=N N≡N -1 435 kJ mol 389 kJ mol 1 163 kJ mol 1 418 kJ mol 1 946 kJ mol 1 A - - - - (1) Na(g) + e → Na (g) (2) Mg(g) + e → Mg (g) (3) Cl(g) + e → Cl (g) (4) Ar(g) + e → Ar (g) - - - - (1) and (2) only C -122 kJ D -1084 kJ C (4) only E -1770 kJ D (1), (2) and (3) only E (1), (2) and (4) only 33 Which of the following elements has the highest boiling point? *B (2) and (4) only 36 Exactly 10.0 g H2O(s) at 0oC is placed on top of 0.100 kg Cu(s) at 100oC. What is the final temperature of the combined system (water plus copper), if no heat is lost to the surroundings? N2 *A 6.9oC B F2 B 43oC C Cl2 C 21oC D Br2 D 35oC E 65oC A *E I2 Energy is always released when an electron is added to a main group atom, except when an electron is added to a group 2 or 18 atom. Atoms in group 2 have completely filled subshells (s2) and atoms of group 18 have completely filled shells. Heat capacity of Cu(s) is 0.39 J g-1 oC 1 The heat of fusion of ice is 334 J g 1. Heat capacity of H2O(l) is 4.18 J g-1 oC 1 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /7 37 When 5.0-g of an impure sample of CaCl2 was treated with excess AgNO3(aq), 0.50 g of dry AgCl was obtained. What is the mass percentage of CaCl2 in the impure sample? A 40 What is the ratio x:y when the equation below is properly balanced? - 15% CaCl2, 110.98 g mol 1 AgCl, 143.35 g mol -1 x Sn2+(aq) + y Ag+(aq) → n Sn4+(aq) + m Ag(s)? A 1:1 B 2:1 B 10% C 7.7% *C 1:2 D 5.0% D 3:4 *E 3.9% E 4:3 38 What is the H-N-H bond angle in ammonia, NH3? (Choose the closest value.) A 72o B 90o *C 109o D 120o E 180o 39 Which of the following is the correct Lewis (i.e., electron dot) structure for the N2O molecule? A N N O B N N O C N N O Of the choices provided, only D has the correct number of valence electrons (16) and gives each atom an octet. *D N N O The “true” structure of N2O is a resonance hybrid of at least three resonance structures. E N N O 2004 UNIVERSITY OF WATERLOO AVOGADRO EXAM /8