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AVOGADRO EXAM 2012 UNIVERSITY OF WATERLOO DEPARTMENT OF CHEMISTRY 17 MAY 2012 TIME: 75 MINUTES This exam is being written by several thousand students. Please be sure that you follow the instructions below. We'll send your teacher a report on your performance. Top performers are eligible for a prize. The names of the top 200 students will be published in the September issue of Chem 13 News. 1. Print your name here: 2. Print your school name and city on your STUDENT RESPONSE sheet. 3. Select, and enter on the STUDENT RESPONSE 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 4 Any other Ontario student Code 5 Manitoba or Saskatchewan high school student Code 6 Québec high school student Code 7 Code 8 not used Alberta or British Columbia high school student Code 9 New Brunswick, Newfoundland, Nova Scotia, or Prince Edward Island high school student Code 10 Northwest Territories, Nunavut, or Yukon high school student 4. Print your name (last name, first name and optional middle initial) on the STUDENT RESPONSE sheet. Also fill in the corresponding circles below your printed name. 5. Carefully detach the last page. It is the datasheet. 6. 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. 7. 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 11 High school student outside Canada Code 12 Teacher Carefully detach the last page. It is the Data Sheet. AVOGADRO EXAM 2012 - Answers 1 How many protons are there in a single A 35 2 − 16 S ion? 5 14 What volume does 3.20 grams of methane gas, o CH4(g), occupy at 0 C and 101.325 kPa? Choose the closest answer. *B 16 C 18 D 19 E 33 A 1.12 L B 2.24 L C 3.40 L *D 4.48 L E 2 22.4 L + The combination of hydronium (H3O ) ions and − hydroxide (OH ) ions to form water molecules is called A B 6 Which of the following substances has a normal o boiling point higher than 500 C? precipitation A propane, C3H8 B bromine, Br2 C mercury, Hg electrolysis *C neutralization D hydrogenation E hydrolysis *D sodium chloride, NaCl E 3 4 Which of the following occurs when Na2O is added to water? 7 sulfuric acid, H2SO4 −1 Elemental gold, Au(s), has a density of 19.3 g mL at 25°C. What is the volume of 42.5 grams of Au(s)? A The water freezes. A B A gas is released. *B 2.20 mL C A black precipitate is formed. C 23.2 mL *D Heat is liberated. D 61.8 mL E E 820 mL A white precipitate is formed. Isotopes differ in A 8 atomic number *B number of neutrons C number of electrons D number of protons E nuclear charge 2 / AVOGADRO EXAM © 2012 UNIVERSITY OF WATERLOO 0.454 mL o At 25 C and 101.325 kPa, the element Sn is A a liquid with a low vapour pressure B a reactive, colourless gas C a liquid with a high vapour pressure D a solid that is a poor conductor of heat *E a solid that is a good conductor of electricity 9 o A 10.0 L container has a sample of O2(g) at 25 C and 51 kPa. A second 10.0 L container has a o sample of CH4(g), also at 25 C and 51 kPa. Assuming ideal gas behaviour, which of the following statements concerning these two samples is correct? 12 A solution contains H2O2 in water. Complete decomposition of the H2O2 in 170 g of this solution o yields 5.6 L of O2(g), measured at 0 C and 101.325 kPa. What is the percentage by mass of H2O2 in this solution? Choose the closest answer. *A 10% (1) They contain the same number of molecules. (2) They have the same density. (3) The molecules in the two samples have the same average kinetic energy. A (1) and (2) B (2) and (3) (1) only E (3) only 20% C 5.0% D 3.0% E 1.0% 13 A handbook gives the specific heat of copper (Cu) −1 o −1 as 0.385 J g C . What is the specific heat −1 −1 expressed in J g K ? Choose the closest value. *C (1) and (3) D B A 105 J g −1 −1 K −1 *B 0.385 J g −1 10 What volume of 6.00 mol L HBr(aq) is required to −1 make 1.00 L of 2.40 mol L HBr(aq)? A 1.00 L B 0.600 L *C 0.400 L D 0.200 L E 0.167 L −3 C 1.41×10 D 2.60 J g E 9.51×10 −1 −3 −1 K −1 Jg −1 K −1 K −1 Jg −1 K 14 Element X forms the stable compounds XS, XSO4 and X(NO3)3. Which of the following could X represent? 11 The specific heats of gold and copper are 0.13 and −1 o −1 0.39 J g C , respectively. If 1.0 g samples of each, o initially at 25 C, are placed in the same beaker of hot water, A the copper will have the highest final temperature B the gold will absorb the greatest quantity of heat A carbon B magnesium C sodium D zinc *E iron 15 Which of the following has a planar, triangular shape? *C the copper will absorb the greatest quantity of heat − *A NO3 D the gold will have the highest final temperature B CO2 E the temperature change for the copper will be about three times that of the gold C NH3 D BeH2 E SO3 2− © 2012 UNIVERSITY OF WATERLOO AVOGADRO EXAM / 3 16 What is the minimum mass of oxygen gas required to react with exactly 20 grams of hydrogen gas, assuming these gases react to form water? Choose the closest answer. 20 What are the most probable products of the combustion of CH3CH2SH in oxygen? A CH4 and H2S CO2 and H2S A 20 g B B 40 g *C CO2, H2O and SO2 C 80 g D CO2, H2O and H2SO4 E CH4, H2O and SO2 *D 160 g E 320 g 21 How many moles of Cl2 are required to oxidize exactly 2+ 3+ one mole of Fe to one mole of Fe ? 17 Typically, a binary salt may be formed between *A 0.5 moles A an s-block cation and a d-block anion B a p-block cation and an s-block anion C a d-block cation and an s-block anion D a p-block cation and a d-block anion B 1 mole C 1.5 moles D 2 moles E 3 moles *E an s-block cation and a p-block anion −1 18 Where in the periodic table does one find the atoms with the smallest atomic radius? A 22 The pH of a 0.10 mol L aqueous solution is 5.1. Which of the following might be the solute? upper left A NaCl B HCl C HNO3 D NH3 *B upper right C lower left D lower right E in the first long period (fourth row) 19 Which of the following pairs of substances are allotropes? A CH3CH2OH and CH3OCH3 B Fe(NO3)2 and Fe(NO3)3 C NaCl and KCl *E NH4Cl 23 The third ionization energy of an element, X, is the energy required to *D O2 and O3 E 234 U and A remove one mole of electrons from one mole of X atoms B remove three moles of electrons from one mole of X atoms C remove one mole of electrons from one mole of 3+ X ions 238 U *D remove one mole of electrons from one mole of 2+ X ions E 4 / AVOGADRO EXAM © 2012 UNIVERSITY OF WATERLOO add three moles of electrons to one mole of X atoms 28 What of the following is named copper (II) chloride? 24 What is the oxidation state of sulfur in H2S2O6? A +4 *A CuCl2 *B +5 C +6 D +7 E +10 25 A 1.0 L sample of N2(g) has a pressure of exactly 100 kPa. A 2.0 L sample of O2(g) has a pressure of 50 kPa at the same temperature. The samples are mixed and forced into a 1.0 L container. Assuming that no reaction occurs and that the temperature remains constant, what is the final pressure of the mixture? B Cu2Cl C (CuCl)2 D CuCl E Cu2Cl2 29 What mass of Na2CO3 is needed to make 5.00 L of a + −1 solution having [Na ] = 0.100 mol L ? A 0.500 g B 5.30 g 10.6 g A 25 kPa C B 50 kPa *D 26.5 g C 100 kPa E D 150 kPa 53.0 g 30 Which of the following statements concerning the reaction below is true? *E 200 kPa Mg + CuSO4 → MgSO4 + Cu 26 Which of the following atoms has the greatest number of unpaired electrons in its ground electronic state? A Magnesium is reduced. B Magnesium is the oxidizing agent. C Sulfur is oxidized. *D Co D Sulfur is reduced. E *E Copper sulfate is the oxidizing agent. A Sc B Al C Si Zn −1 27 If 1.0 mol L NaX(aq) contains 7.4% solute by mass, what is the molar mass of X? Choose the closest answer. Assume the density of this solution is approximately equal to that of water, 1.0 g/mL. A 31 The noble gas atoms show only a limited tendency to form covalent bonds with other atoms. Which of the following pairs of atoms show the greatest tendency to form a covalent bond? −1 17 g mol A neon and fluorine B neon and iodine −1 *B 51 g mol C −1 74 g mol −1 D 98 g mol E 120 g mol −1 *C xenon and fluorine D xenon and cesium E xenon and iodine © 2012 UNIVERSITY OF WATERLOO AVOGADRO EXAM / 5 32 A gaseous mixture consists of 25% H2, 25% N2, 25% O2 and 25% Cl2 by mass. Which gas has the o highest partial pressure at 227 C and 101 kPa? Molar masses, −1 (in g mol ): 2.016 H2, 28.02 N2, 32.00 O2, Cl2, 70.90 *A H2 B N2 C O2 D Cl2 E The partial pressures are equal. −1 35 When 0.100 L of 1.00 mol L HCl(aq) is mixed with −1 0.100 L of 1.00 mol L NaOH, the temperature of o the solution rises by 8.5 C. Assuming no heat loss to the container or the surroundings, what is the heat of reaction for the following reaction? (You may also assume that, for these aqueous solutions, the −1 density is about 1.0 g mL and the heat capacity is −1 o −1 about 4.2 J g C .) − H (aq) + OH (aq) → H2O(l) + −1 33 In an experiment,1.0 mol L HCl(aq) is added −1 millilitre-by-millilitre to 50.0 mL of 1.0 mol L NaOH(aq) until the total volume reaches 150.0 mL. Which of the following statements concerning this experiment is correct? −1 A −4.8 kJ mol B −7.1 kJ mol C −18 kJ mol D −36 kJ mol −1 −1 −1 −1 A The pH increases approximately linearly with the volume of HCl added. B The pH decreases approximately linearly with the volume of HCl added. C Initially, the pH decreases approximately linearly with the volume of HCl added, and then decreases abruptly as the total volume approaches 50.0 mL. *E −71 kJ mol 36 Which expression correctly represents a chemical reaction between calcium hydroxide and carbon dioxide? A *B Ca(OH)2 + CO2 → CaCO3 + H2O *D Initially, the pH decreases approximately linearly with the volume of HCl added, and then decreases abruptly as the total volume approaches 100.0 mL. E Initially, the pH increases approximately linearly with the volume of HCl added, and then increases abruptly as the total volume approaches 100.0 mL. 34 An oxide of potassium contains 45.0% oxygen by mass. What is the simplest formula of this oxide? A KO B K2O CaOH + CO2 → CaHCO2 C Ca(OH)2 + CO2 → CaHCO3 + H2O D 2 CaOH + 2 CO2 → 2 CaCO3 + H2O E Ca(OH)2 + 2 CO2 → Ca(CO3)2 + H2O 37 Which of the following pairs of atoms will form a bond with the greatest covalent character? A carbon and oxygen B hydrogen and oxygen C carbon and chlorine D hydrogen and chlorine *C KO2 D K2O3 E KO3 6 / AVOGADRO EXAM © 2012 UNIVERSITY OF WATERLOO *E hydrogen and carbon 38 If an element X forms an oxide with the formula XO2, then what is the expected formula for the fluoride of element X? A XF B XF2 C XF3 *D XF4 E X2F 39 A 0.9300 g sample of a mixture of NaCl and MgCl2 was dissolved in water. Addition of excess AgNO3(aq) caused all of the chloride ion to precipitate as AgCl(s). The dry precipitate weighed 2.676 g. What was the percentage by weight of NaCl in the original mixture? A between 0 and 19.9% *B between 20.0 and 39.9% C between 40.0 and 59.9% D between 60.0 and 79.9% E between 80.0% and 100% Molar masses (in g mol−1): NaCl, 58.44 MgCl2, 95.21 AgCl, 143.35 40 If the Kelvin temperature of a gas increases by a factor of four, then the average speed of molecules A increases by a factor of four B decreases by a factor of four *C increases by a factor of two D decreases by a factor of two E is unchanged © 2012 UNIVERSITY OF WATERLOO AVOGADRO EXAM / 7 DATA SHEET AVOGADRO EXAM 2012 DETACH CAREFULLY 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 24.31 20 Ca 40.08 38 Sr 87.62 56 Ba 137.3 88 Ra 226 3 4 3B 4B 21 22 Sc Ti 44.96 47.88 39 40 Y Zr 88.91 91.22 57-71 72 La-Lu Hf 178.5 89-103 104 Ac-Lr Rf 57 La 138.9 89 Ac (227) 58 Ce 140.1 90 Th 232.0 5 5B 23 V 50.94 41 Nb 92.91 73 Ta 180.9 105 Db 59 Pr 140.9 91 Pa 231.0 6 6B 24 Cr 52.00 42 Mo 95.94 74 W 183.9 106 Sg 60 Nd 144.2 92 U 238.0 7 7B 25 Mn 54.94 43 Tc (98) 75 Re 186.2 107 Bh 61 Pm (145) 93 Np 237.0 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 Ds 62 63 64 Sm Eu Gd 150.4 152.00 157.3 94 95 96 Pu Am Cm (244) (243) (247) Constants: mol−1 6.022 × 10 R = 0.082058 atm L K−1 mol−1 = 8.3145 kPa L K−1 mol−1 = 8.3145 J K−1 mol−1 23 −14 Kw = 1.0×10 F 96 485 C mol Equations: 65 Tb 158.9 97 Bk (247) 12 2B 30 Zn 65.38 48 Cd 112.4 80 Hg 200.6 112 Cn 66 Dy 162.5 98 Cf (251) 67 Ho 164.9 99 Es (252) 14 4A 6 C 12.01 14 Si 28.09 32 Ge 72.59 50 Sn 118.7 82 Pb 207.2 68 Er 167.3 100 Fm (257) 15 5A 7 N 14.01 15 P 30.97 33 As 74.92 51 Sb 121.8 83 Bi 209.0 69 Tm 168.9 101 Md (258) 16 6A 8 O 16.00 16 S 32.07 34 Se 78.96 52 Te 127.6 84 Po (209) 70 Yb 173.0 102 No (259) 17 7A 9 F 19.00 17 Cl 35.45 35 Br 79.90 53 I 126.9 85 At (210) 71 Lu 175.0 103 Lr (260) Conversion factors: NA = = 11 1B 29 Cu 63.55 47 Ag 107.9 79 Au 197.0 111 Sg 13 3A 5 B 10.81 13 Al 26.98 31 Ga 69.72 49 In 114.8 81 Tl 204.4 1 atm = 101.325 kPa = 760 Torr = 760 mm Hg o 0 C = 273.15 K (at 298 K) −1 PV = nRT k t1/2 = 0.693 pH = pKa + log ( [base] / [acid] ) 8 / AVOGADRO EXAM © 2012 UNIVERSITY OF WATERLOO x= −b ± b 2 − 4ac 2a 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)