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551-534 Chemistry Comprehensive Exam Number 55 GUIDE Secondary 5 September, 2005 Guide 1. Page 1 GENERAL INFORMATION 1.1 Program: Chemistry, Secondary V 1.2 Origin: Mathematics and Science & Technology Committee, 2005 Computerization and graphics: Martine Sanscartier Revision: Patricia Juliano, BIM, Société GRICS 1.3 Time allotted: 2 hours 30 minutes 1.4 Number of questions: 29 distributed as follows: 14 multiple choice 15 constructed response (students select 11) Structure of the Exam: 551-534.E55 Part A: Fourteen (14) multiple-choice questions worth 4 marks each for a total of 56%. Part B: Four (4) problems on the gases and their applications of which the student is required to answer three (3). Each question is worth 4 marks for a total of 12%. Part C: Four (4) problems on energy in chemical reactions of which the student is required to answer three (3). Each question is worth 4 marks for a total of 12%. Part D : Three (3) problems on rate of chemical reactions (kinetics) of which the student is required to answer two (2). Each question is worth 4 marks for a total of 8%. Part E : Four (4) problems on chemical equilibrium of which the student is required to answer three (3). Each question is worth 4 marks for a total of 12%. Guide 1.5 2. Page 2 Authorized material: - drawing instruments, graph paper - scientific calculator with or without graphic display - list of formulas and quantities included in the examination booklet - periodic table of the elements included in the examination booklet - a table of reduction potentials included in the examination booklet DESCRIPTION OF EXAM The following table matches each of the examination questions with the corresponding dimension of the definition of the domain that was used for the examination. Exam Specifications Topics Gases and their Applications 28% Energy in Chemical Reactions 28% Rate of Chemical Reactions 16% Equilibrium in Chemical Reactions 28% Mastery of Concepts 28% 2, 4 5, 8 9, 10 13 Mastery of Applications 28% – 40%* 1, 3 6, 22 23, 24 11, 12, 14, 28 Mastery of Problem- Solving Techniques 32% – 44%* 15, 16, 17, 18 7, 19, 20, 21 25 26, 27, 29 Skill The numbers on the centre of each box above represent the question numbers in the examination. *Depending on questions chosen. The examination consists of the following types of questions: 14 multiple-choice questions (numbers 1 - 14) that test the student's mastery of concepts and applications. 11 of 15 constructed-response questions (numbers 15 - 29) that test the student's mastery of concepts, applications and problem solving. Student selection of problems When a student answers more than the number of questions required, without indicating which ones are to be corrected, only the first ones are to be corrected. Thus, for example, if a student is to choose two out of three questions and answers all three, only the first two are to be corrected. 551-534.E55 Guide Page 3 ITEM SPECIFICATIONS Question MOD.TO.IO T S D Part A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 [2153] [2154] [2155] [2156] [2157] [2158] [2159] [2160] [2161] [2162] [2163] [2164] [2165] [2166] M02.01.01 M02.02.02 M02.02.04 M02.02.09 M03.03.02 M03.01.01 M03.02.04 M03.02.05 M04.02.01 M04.02 M05.01 M05.01.03 M05.02.02 M05.03 M M M M M M M M M M M M M M C C C C C C A A C C C A A A E M E E M E M D E E E M E E Part B 15 16 17 18 [2167] [2168] [2169] [2170] M02.02.02 M02.02.09 M02.02.07 M02.03.02 E E E E A P P C D M M E Part C 19 20 21 22 [2171] [2172] [2173] [2174] M03.02.06 M03.02.03 M03.03 M03.03.03 E E E E P A A A M M M D Part D 23 [2175] M04.01.02 24 [2176] M04.02.02 25 [2177] M04.03 E E E A C A M M M Part E 26 27 28 29 E E E E P P P P M D M M [2178] [2179] [2180] [2181] 551-534.E55 M05.02.06 M05.02.05 M05.03.04 M05.03.05 Legend: MOD : Modules M02: Gases and Their Applications M03: Energy in Chemical Reactions M04: Rate of Chemical Reactions M05: Equilibrium in Chemical Reaction TO: Terminal objective IO: Intermediate objective T: Type M : multiple-choice E : extended-answer (constructed response) S: Skill C : Mastery of Concepts A : Mastery of Application P : Mastery of Problem-Solving Techniques D: Level of difficulty E: Easy M: Medium D: Difficult Guide 3. CORRECTION KEY Part A 4 marks or 0 marks 1 D 2 D 3 C 4 A 5 C 6 D 7 C 8 A 9 A 10 D 11 B 12 C 13 C 14 B 551-534.E55 Page 4 Guide Page 5 GUIDELINES FOR CORRECTING CONSTRUCTED-RESPONSE QUESTIONS Below is an explanation of the terms found in the marking scale to be used for scoring the answers to the constructed response questions in the examination. It is IMPORTANT that the teacher read this information carefully before correcting the examination. Constructed-response questions usually consist of two parts: the procedure used to solve the problem and the answer. Thus, a constructed-response question should be corrected in two steps. Step 1 Analyze the work to understand the procedure used by the student, and then decide if the procedure is appropriate or not. A procedure is appropriate if the steps presented could lead to the correct answer. A procedure is partially appropriate if the steps presented do not lead to the correct answer, but include at least one step that is relevant and correct. A procedure is inappropriate if none of the steps presented are relevant or if the student has not shown any work. Step 2 If the procedure is deemed appropriate, then evaluate the answer. If the answer is incorrect, identify the type of error made. The error is considered minor if it is an error in calculation or transcription, if the unit of measurement is incorrect or missing, or if the student has rounded off a number incorrectly. The error is considered major if a law, rule, or formula has been applied incorrectly. No marks are allotted for a correct answer when the procedure used is inappropriate. 551-534.E55 Guide Page 6 Part B 15 Example of an appropriate and complete solution P1V1 n1T1 = P2V2 n2T2 P1 (2 L) n (293 K) = P2 (0.5 L) 0.5 n (253 K) P1 (2 L) n (293 K) = P2 (0.5 L) 0.5 n (253 K) 2L 253 K (0.5 n) P1 = n (293 K) (0.5 L) 1.73 P1 P2 = P2 Answer: The ratio is 1.73 : 1. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 16 Page 7 Example of an appropriate and complete solution Step 1: Find mass of nitroglycerine. 1.59 g d= mL mass 1.59 g = mL 100 mL 159 g of nitroglycerine present in 100 mL. Step 2: Find moles of H2O gas M for nitro glycerine = 227 g mol 159 g = 0.70 mol of nitro glycerine 227 g mol 4 mol C3H5 ONO2 3(l) 0.70 mol C3H5 ONO2 3(l) = 10 mol H 2 O (g) x mol H 2 O (g) x = 1.75 mol H2O(g) Step 3: Find volume H20(g) Use either: A. Ideal gas Law, PV= nRT or B. Avogadro, at STP 1 mol gas = 22.4 L Answer: The volume of water vapour produced is 39 L. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. (i.e. Student did not convert to mass.) 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 17 Page 8 Example of an appropriate and complete solution Mass of unknown gas 47.61 g 46.02 g = 0.69 g PV = n = = = nRT PV RT 46.9 kPa 0.296 L kPa L 8.31 18 273 mol K 0.00574 mols unknown gas Molar mass of unknown gas 0.69 g 0.00574 mols = 120.2 g/mol Therefore, the unknown gas is CF2Cl2 Answer: The unknown gas is most likely CF2Cl2 because its molar mass is 121 g/mol. 4 marks Appropriate and correct answer. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 18 Page 9 Example of an appropriate and complete solution a) Temperature has a direct effect on the average kinetic energy of a molecule. Colder temperatures imply that the molecules will move at a slower rate. Since the molecules are moving at a slower rate they will diffuse (spread out) at a slower pace. b) The molecular mass of helium is less than the molar mass of oxygen. Because both gases have the same kinetic energy, the velocity of the helium molecules must be greater than the velocity of the helium molecules must be greater than the velocity of the oxygen molecules. Therefore helium will diffuse more rapidly. a) 1 mark for temperature affecting energy 1 mark for energy resulting in slower rate b) 1 mark for comparing the molar mass of the two gases 1 mark for correctly relating mass, velocity, and rate of diffusion 551-534.E55 Guide Page 10 Part C 19 Example of an appropriate and complete solution Twater = 26 °C 14 °C = 12 °C Tx = 95 °C 26 °C = 69 °C MwCw Tw = MxCx Tx M C ΔTw Cx = w w M x ΔTx 65 g 12 C 4.19 J/g C = 150 g 69 C = 0.32 J/g °C Answer: The specific heat capacity of the unknown metal is 0.32 J/g °C. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. (i.e. Students reversed the T’s or reversed the constants.) 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 20 Page 11 Example of an appropriate and complete solution 1. Moles of NaOH(aq) used n or n = MV V (1.0 mol/L)(50.0 mL/1000mL) = 0.050 moles M= 2. Heat absorbed Q = mcT (70.0 g)(4.19 J/(goC)(29.8-22.3 °C) = 2200 J 3. Since Q for the surroundings is positive, Q for the system must be negative (or -2200 J) 4. Molar heat of neutralization Q H = n - 2200 J NaOH 0.050 moles -44000 J or -44 kJ/mol NaOH Answer: H is -44 kJ/mol NaOH. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error, or units of measurement missing. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 21 Page 12 Example of an appropriate and complete solution Moles of diamond used 1.00 g = 8.33 10-2 mol C 12.01 g/mol Q = mcwater T = (150.0 g)(4.19 J/(g°C)(74.5 – 22.0 °C) = 3.30 104 J Q for diamonds is -3.30 104 J or -3.30 101 kJ Molar Heat of Combustion Q - 3.30 101 kJ = n 8.33 10 2 moles = Answer: -396 kJ/mol H is -396 kJ/mol or -396 000 J/mol. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error or omission of the negative sign. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 22 Page 13 Examples of an appropriate and complete solution N+3H 1118 kJ - Enthalpy or Ep (kJ/mol) 0.0 - 1 2 3 N2 + 2 H2 H NH3 -46 - Reaction coordinate Criteria: 1. y axis is labelled correctly, including units and values. 2. Correct H. 3. Activation energy values are correctly indicated. 4. Reactants, activated complex, and products are correctly labelled. Allot 1 mark per criterion. Note: 551-534.E55 Students may use arrows to indicate the difference in energy levels rather than indicating numbers on the y axis. Guide Page 14 Part D 23 Example of an appropriate and complete answer Rate of N2 consumption 0.60 4.00 mol/L = -0.068 or -6.8 102 mol/L/min 50 min Rate of NH3 production 2 mol NH3 - 6.8 10-2 mo l/L = 1.4 101 mol/L/min 1 mol N 2 min Answer: 24 The average rate of ammonia production is 1.4 101 mol/L/min. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error or an incorrect or missing unit of measurement in the answer. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. Example of an appropriate and complete solution (I) (II) (III) NO OH OH and NO Allot 1 mark for each correct substance listed. Deduct 1 mark for each incorrect substance listed. 551-534.E55 Guide 25 Page 15 Example of an appropriate and complete solution a) Data Table Time (min) 0.0 0.2 0.4 0.6 0.8 1.0 [I-] (mol/L) 0.0800 0.0400 0.0200 0.0100 0.0050 0.0025 [I2] (mol/L) 0 0.02 0.03 0.035 0.0375 0.0387 3 marks Deduct 1 mark per error b) Calculate the rate Rate = 0.03875 0 mol/L 1.0 0.0 min 0.03875 mol/L = 1.0 min = 0.03875 mol/L/min = 3.88 10-2 = 3.9 10-2 mol/L/min Answer: The average rate of reaction for the production of I2(aq) is 3.9 10-2 mol/L/min. 1 mark 551-534.E55 Guide Page 16 Part E 26 Example of an appropriate and complete answer I C E Kc 4 NH3(g) + 3 O2(g) 0.0150 0.0150 -3.92 103 -2.94 103 1.11 102 1.21 102 = 2 N2(g) + 6 H2O(g) 0 0 +1.96 103 +5.88 103 +1.96 103 +5.88 103 N 2 2 H 2O 6 NH3 4 O2 3 1.96 10 = 1.11 10 3 2 5.88 10 mol/L 1.21 10 2 mol/L 4 3 3 2 mol/L mol/L 6 3 = 6.01 106 Answer: The Kc for the reaction at this temperature is 6.01 106. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 27 Page 17 Example of an appropriate and complete solution Butanoic Acid HA 0.15 -1.51 103 0.148 I C E Ka 1.51 10 3 mol/L 0.148 mol/L 1.54 105 = = H+ 0 1.51 103 1.51 103 + A H+ 0 1.32 105 1.32 105 + A 0 + 1.51 103 1.51 103 2 Hydrofluoric Acid First find H+ KW = 1.32 105 7.59 10 10 HA 0.035 -1.32 105 0.035 I C E Ka = = Answer: 1.32 10 5 mol/L 0.0350 mol/L 4.98 109 0 + 1.32 105 1.32 105 2 Butanoic acid is the stronger of the two. Note: Comparing percent ionization is an acceptable justification. 4 marks Appropriate procedure and correct answer. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure, regardless of the answer. 551-534.E55 Guide 28 Page 18 Example of an appropriate and complete answer a) e Anode, Mg V Cathode, Ag salt bridge Mg2+ Mg(s) Mg2+(aq) + 2e E° = 2.37 V Ag+ Ag+(aq) + e Ag(s) E° = 0.80 V b) E°cell : 2.37 V + 0.80 V = 3.17 V c) To increase the cell potential, the concentration of AgNO3 should be increased or the concentration of Mg(NO3)2 should be decreased. 4 marks Appropriate and complete procedure. 3 marks Appropriate procedure with a minor error such as calculation or transcription error. 2 marks Appropriate procedure with a major error such as the incorrect application of a law, formula or rule. 1 mark Partially appropriate and correctly completed procedure. 0 marks Inappropriate procedure or did not show the procedure. 551-534.E55 Guide 29 Page 19 Example of an appropriate and complete answer 1. 2. 3. Fe2+ + 2e Fe Cu Cu2+ + 2e 0.44 V 0.34 V 0.78 V Maintains integrity of pipes (1 mark) Pb2+ + 2e Pb Cu Cu2+ + 2e 0.13 V 0.34 V 0.47 V Maintains integrity of pipes (1 mark) 2 Ag+ + 2e 2 Ag Cu Cu2+ + 2e + 0.80 V 0.34 V + 0.46 V Answer: 551-534.E55 Copper pipe corrodes (1 mark) The technician did cause chemical reaction to occur in the pipes because silver nitrate corrodes copper pipes. (1 mark) 551-534 Chemistry Comprehensive Exam Number 55 Question Booklet Secondary 5 September, 2005 Question Booklet Page 1 INSTRUCTIONS 1. Write the required information on the title page of the Answer Booklet. 2. Answer all questions in the Answer Booklet. Each question is worth four marks. 3. In Part B, you are to answer 3 of the 4 questions. 4. In Part C, you are to answer 3 of the 4 questions. 5. In Part D, you are to answer 2 of the 3 questions. 6. In Part E, you are to answer 3 of the 4 questions. 7. You may use drawing instruments, graph paper and a scientific calculator with or without graphing display. 8. You may refer to the lists of formulas, quantities, and tables included in this Question Booklet. The use of any other source of reference is strictly forbidden. 9. Hand in both the Question Booklet and the Answer Booklet at the end of the exam session. Note: Figures are NOT necessarily drawn to scale. Time allotted: 2 hours 30 minutes 551-534.E55 Question Booklet 551-534.E55 Page 2 Question Booklet Page 3 FORMULAS Q = mcT PV = n RT P1V1 P2V2 = n1T1 n2T2 PHYSICAL CONSTANTS SYMBOL c H 2O VALUE NAME Specific heat capacity of water 4190 J/(kg°C) or H 2O R 551-534.E55 Density of water Molar gas constant 4.19 J/(g°C) 1.00 g/mL 8.31 kPa L/(molK) Question Booklet Page 4 Standard Reduction Potentials ION CONCENTRATION of 1 mol/L at 25°C and 101.3 kPa. Reduction Half-reaction F2(g) Au3+(aq) Cl2(g) Br2(aq) Br2(l) Ag+(aq) Hg 2+(aq) Fe3+(aq) I2(s) Cu+(aq) Cu2+(aq) 2H+(aq) Pb2+(aq) Sn2+(aq) Ni2+(aq) Co2+(aq) Fe2+(aq) Cr3+(aq) Zn2+(aq) Cr2+(aq) Mn2+(aq) Al3+(aq) Be2+(aq) Mg2+(aq) Na+(aq) Ca2+(aq) Sr2+(aq) Ba2+(aq) Cs+(aq) K+(aq) Rb+(aq) Li+(aq) 551-534.E55 + 2e+ 3e+ 2e+ 2e+ 2e+ e+ 2e+ e+ 2e+ e+ 2e+ 2e+ 2e+ 2e+ 2e+ 2e+ 2e+ 3e+ 2e+ 2e+ 2e+ 3e+ 2e+ 2e+ e+ 2e+ 2e+ 2e+ e+ e+ e+ e- 2F-(aq) Au(s) 2Cl-(aq) 2Br-(aq) 2Br-(aq) Ag(s) Hg(l) Fe2+(aq) 2I-(aq) Cu(s) Cu(s) H2(g) Pb(s) Sn(s) Ni(s) Co(s) Fe(s) Cr(s) Zn(s) Cr(s) Mn(s) Al(s) Be(s) Mg(s) Na(s) Ca(s) Sr(s) Ba(s) Cs(s) K(s) Rb(s) Li(s) Reduction Potential (V) E° = + 2.87 E° = + 1.50 E° = + 1.36 E° =+ 1.09 E° =+ 1.07 E° = + 0.80 E° = + 0.78 E° = + 0.77 E° = + 0.53 E° = + 0.52 E° = + 0.34 E° = + 0.00 E° = - 0.13 E° = - 0.14 E° = - 0.26 E° = - 0.28 E° = - 0.44 E° = - 0.74 E° = - 0.76 E° = - 0.91 E° = - 1.18 E° = - 1.66 E° = - 1.85 E° = - 2.37 E° = - 2.71 E° = - 2.87 E° = - 2.89 E° = - 2.91 E° = - 2.92 E° = - 2.93 E° = - 2.98 E° = - 3.04 Question Booklet Page 5 Part A Questions 1 to 14 Blacken the letter that corresponds to your answer in the answer booklet. 1 2 Which of the following statement is TRUE? A) Gas molecules are strongly attracted to each other. B) At a given temperature, the number of degrees Celsius is always larger than the number of Kelvins. C) For a fixed amount of gas at a constant pressure, if temperature increases, volume decreases. D) For a fixed amount of gas at a constant volume, if temperature increases, pressure increases. The Kinetic Molecular Theory describes an ideal gas model. Among the main features of this model are: (I) (II) (III) (IV) Gases consist of molecular particles moving at any given instant in straight lines. Molecules collide with each other and with the container walls without loss of kinetic energy. The average kinetic energy of gas molecules is directly proportional to the Kelvin temperature. Gas molecules are very widely spaced, relative to the size of the molecules. Which two of these Kinetic Molecular Theory features can be used to explain why gas bubbles always rise through a liquid and become larger as they move upward? 3 A) (I) and (III) C) (II) and (III) B) (I) and (IV) D) (II) and (IV) There are n molecules in 250 cm3 of hydrogen gas (H2), at a certain temperature and pressure. How many molecules are in 1.0 L of oxygen gas (O2) under the same conditions of temperature and pressure? A) n C) 4n B) 2n D) 8n 551-534.E55 Question Booklet 4 Page 6 Consider the following two situations concerning gases. (I) Included on all spray cans is a warning to not incinerate the can even if it is empty, and to always store it below 40°C. (II) When you examine the tires on your bicycle before you start out in the morning, you note that they appear slightly soft. However, after riding for several hours, they get harder. Which of the following graphs can be used to explain these two situations? A) C) P P T B) D) V T 551-534.E55 V n T Question Booklet 5 Page 7 The enthalpy diagram below shows the energy involved in the formation of CO2(g). Energy (kJ/mol) C(s) + O2(g) CO2(g) Time Once the reaction above has been initiated, which of the following statements is true? 6 A) The formation of CO2(g) constitutes an endothermic reaction. B) The formation of CO2(g) does not result in energy from the system being transferred into the surroundings. C) The formation of CO2(g) results in energy from the system being transferred into the surroundings. D) In the formation of CO2(g) the enthalpy of the products will be greater than the enthalpy of the reactants. Everyday, phenomena take place all around us. Which of the following may be identified as exothermic processes? 1. 2. 3. 4. 5. Dew forming on blades of grass Melting snow and ice on a driveway by adding salt Drying a wet T-shirt on a clothesline Freezing meat to preserve it Burning propane gas in a stove A) 2 and 3 C) 1, 2 and 3 B) 4 and 5 D) 1, 4 and 5 551-534.E55 Question Booklet 7 Page 8 Ethane, C2H6, can be decomposed into ethene, C2H4, and hydrogen gas: C2H6(g) C2H4(g) + H2(g) Using the following equations, determine the enthalpy change for the decomposition of ethane. 2 H2(g) + O2(g) 2 H2O(l) C2H4(g) + 3 O2(g) 2 H2O(l) + 2 CO2(g) 2 C2H6(g) + 7 O2(g) 6 H2O(l) + 4 CO2(g) 1. 2. 3. 8 H = -572 kJ H = -1401 kJ H = -3100 kJ A) -5073 kJ C) 137 kJ B) -3237 kJ D) 3237 kJ Barbeque propane gas, C3H8, burns according to the following equation: C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) How many grams of propane are needed to provide the 980 kJ required to cook a salmon steak? ∆Hf (kJ/mol) 3 C(s) + 4 H2(g) C3H8(g) -103.8 C(s) + O2(g) CO2(g) -394.0 H2(g) + ½ O2(g) H2O(g) -241.8 A) 21.1 g C) 9.6 g B) 19.1 g D) 10.6 g 551-534.E55 Question Booklet 9 10 Page 9 Which of the following does not affect the reaction rate? A) Nature of products B) Surface area of reactants C) Concentration of reactants D) Presence of a catalyst Consider the following reactions at room temperature: 1. Fe3+(aq) + SCN1-(aq) FeSCN2+ (aq) 2. 4 Fe(s) + 3 O2(g) 2 Fe2O3(s) 3. 8 Fe(s) + S8(s) 8 FeS(s) Which combination below arranges the reactions from slowest to fastest? 11 A) 1 2 3 C) 2 3 1 B) 1 3 2 D) 3 2 1 The equilibrium constant (Kc) for the following reaction is 1.47 103. H3O+(aq) + F-(aq) HF(aq) + H2O(l) At equilibrium, which of the following statements about the reaction is true? A) The concentration of H3O+ and F- would be much larger than HF. B) The concentration of HF would be much larger than H3O+ and F-. C) The concentration of H3O+ , F- and HF would be approximately equal. D) Kc has no effect on concentration. 551-534.E55 Question Booklet 12 Page 10 Consider the following reaction at equilibrium in a closed container: CaCO3(s) CaO(s) + CO2(g) Which of the following statements is true if the volume of the container is increased? 13 A) The concentration of CaCO3 would increase. B) The concentration of CaCO3 would decrease. C) The amount of CO2 would increase. D) The amount of CO2 would decrease. Propanoic acid (CH3CH2COOH which we simplify as HPr) is an organic acid whose salts are used to retard mould growth in foods. The balanced equation is shown below: HPr(aq) + H2O(l) Pr-(aq) + H3O+(aq) Which of the following is the correct expression for the acid dissociation constant? A) B) 14 C) Pr H O D) K a Pr H 3O Ka 3 HPr H 2O Ka Ka Pr H O HPr HPr H 2O Pr H O 3 Consider the following redox reaction: Sr(s) + Mg2+(aq) Sr2+(aq) + Mg(s) Which is the oxidizing agent? A) Sr C) Sr2+ B) Mg2+ D) Mg 551-534.E55 3 Question Booklet Page 11 Parts B, C, D and E of the examination comprise questions for which you must show all your work. Answer these questions in the answer booklet. Show all the work needed to solve the problem: data given, explanations, formulas and calculations. Then write your answer in the space provided. You will be given no marks if you provide the right answer without showing your work. However, you will be given part marks for work that is partially correct. Where necessary, the correct unit of measurement must be included in the answer; however, significant figures will not be considered. Part B Questions 15, 16, 17 and 18 (Answer three questions only.) If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 15, 16 and 17 will be corrected. 15 A student produced H2(g) by performing the following chemical reaction: Mg(s) + 2 HCl(aq) MgCl2(aq) + H2(g) The hydrogen gas produced was collected and stored in a 2.00 L container at 20.0 °C. Half of the original amount of the gas is transferred into a 0.50 L container at -20.0 °C. What is the ratio of the gas pressure in the second container to the initial gas pressure in the first container? Show all your calculations to justify your answer. 16 Nitroglycerine, C3H5(ONO2)3, has a density of 1.59 g/mL. When it explodes, the following reaction takes place: 4 C3H5(ONO2)3 (l) 12 CO2(g) + O2(g) + 6 N2(g) + 10 H2O(g) What volume of water vapour, measured at STP, is produced when 1.0 x 102 mL of nitroglycerine explodes? 551-534.E55 Question Booklet 17 Page 12 The product formed in a controlled fluorination of CHCl3 is a gaseous compound. To identify it, a flask is evacuated and the unknown gas is transferred into the flask. The data below is collected: Volume of evacuated flask 296.0 mL Mass of evacuated flask 46.02 g Mass of flask + unknown gas 46.71 g Pressure 46.9 kPa Temperature 18.0 °C Which of the following is most likely the unknown gas? CFCl3 CF2Cl2 CF3Cl CF4 Show all your calculations and justify your choice. 18 Using the Kinetic Molecular Theory of gases explain why: a) The rate of diffusion of a gas decreases when the temperature is reduced. b) Under the same conditions, the rate of diffusion of helium gas is greater than the rate of diffusion of oxygen gas. 551-534.E55 Question Booklet Page 13 Part C Questions 19, 20, 21 and 22 (Answer three questions only.) If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 19, 20 and 21 will be corrected. 19 An unknown metal with a mass of 150 g and a temperature of 95 °C is placed into a Styrofoam cup containing 65 g of water at a temperature of 14 °C. When the system reaches equilibrium, the resulting temperature is 26 °C. What is the specific heat capacity of the unknown metal? (Assume no loss of heat energy to the surroundings.) 20 A calorimeter is filled with 50.0 mL of 1.0 mol/L NaOH(aq) at an initial temperature of 22.3 °C and 20.0 mL of 2.5 mol/L HCl(aq) is added at this same temperature. After the neutralization reaction comes to completion, the final temperature of the resulting solution is found to be 29.8 °C. Determine the H (kJ/mol) for the neutralization for the reaction with respect to the NaOH(aq) solution. (Assume the density and specific heat for all solutions to be equal to that of water) 551-534.E55 Question Booklet 21 Page 14 A bomb calorimeter contains a 150.0 g of water at an initial temperature of 22.0 °C. When 1.00 g of diamond is burned in the calorimeter to produce CO2, the final temperature of the water reaches 74.5 °C. What is the H (kJ/mol) for the combustion of carbon in the form of diamond? C(diamond) + O2(g) 22 H = ? CO2(g) The Haber process for the formation of ammonia (NH3)) from the elements can be derived from the following equations: 1 2 N2(g) + 3 2 H2(g) N(g) + 3 H(g) Eactivation = 1118 kJ NH3(g) N(g) + 3 H(g) Eactivation = 1164 kJ The Haber process can be written as 1 2 N2(g) + 3 2 H2(g) NH3(g) N(g) + 3 H(g) has been determined to be the activated complex for the overall reaction. Draw an Enthalpy diagram to determine the H for the Haber process. Indicate the H on the diagram. The graph must indicate reactants, products, activated complex, H, and appropriate values. 551-534.E55 Question Booklet Page 15 Part D Questions 23, 24 and 25 (Answer two questions only.) If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 23 and 24 will be corrected. Consider the following graph, illustrating nitrogen consumption. Consumption of Nitrogen Concentration (mol/L) of Nitrogen 23 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0 10 20 30 40 50 60 70 Time (min) In the Haber reaction, nitrogen gas (N2) is combined with hydrogen gas (H2) under extremely high pressure and medium temperature, and using a catalyst (an iron catalyst prepared by reducing magnetite, Fe3O4), to produce ammonia (NH3(g)). N2(g) + 3 H2(g) 2 NH3(g) Using the graph above, calculate the average rate of ammonia production in mol/L/min over the first fifty (50) minutes. 551-534.E55 Question Booklet 24 Page 16 Shown below are several reaction mechanisms involving Ozone gas (O3). (I) NO(g) + O3(g) O(g) + NO2(g) NO2(g) + O(g) NO(g) + O2(g) (II) OHHO2 HO2 + O2(g) OH- + 2O2(g) H(g) + CO2(g) HO2 OH- + NO2(g) NO(g) + O(g) O3(g) + O3(g) + O3(g) (III) CO(g) + OHH(g) + O2(g) HO2 + NO(g) NO2(g) + light energy O(g) + O2(g) For each mechanism, list the substance(s) that could have acted as a catalyst. 25 The reaction below was studied at 25 °C. 2I-(aq) + S2O82-(aq) I2(aq) + 2SO42-(aq) The following data was collected: Time (min) 0.0 0.2 0.4 0.6 0.8 1.0 [I-] (mol/L) 0.0800 0.0400 0.0200 0.0100 0.0050 0.0025 [I2] (mol/L) 0 a) Complete the data table for I2(aq) b) Calculate the average rate of reaction for the production of I2(aq) over the course of the time given. 551-534.E55 Question Booklet Page 17 Part E Questions 26, 27, 28 and 29 (Answer three questions only.) If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not questions 26, 27 and 28 will be corrected. 26 When 0.0150 mol NH3(g) and 0.0150 mol O2(g) are introduced into a 1.00 L container at a certain temperature, the N2 concentration at equilibrium is 1.96 10-3 mol/L. 4 NH3(g) + 3 O2(g) 2 N2(g) + 6 H2O(g) Calculate Kc for the reaction at this temperature. 27 A 0.15 mol/L solution of butanoic acid (CH3CH2CH2COOH) has a H3O+ concentration of 1.51 10-3 mol/L. A 0.035 mol/L solution of hydrofluoric acid (HF) has a OH concentration of 7.59 10-10 mol/L. Which of the two acids is stronger? Justify your answer using appropriate calculations. 28 29 A galvanic cell consists of a Mg electrode in a 1.0 mol/L Mg(NO3)2 solution and a Ag electrode in a 1.0 mol/L AgNO3 solution. a) Draw a diagram of the cell specifying anode, cathode, and direction of electron flow. b) Calculate the standard cell potential of this electrochemical cell. c) Describe one method through which this cell potential may be increased. A newly hired technician at a chemical factory was on night duty and had to decide whether the following solutions could be pumped, one at a time, from one lab to another using copper, Cu, pipes. Iron nitrate Lead nitrate Silver nitrate Fe(NO3)2 Pb(NO3)2 AgNO3 The technician decided to go ahead and pump the three solutions one at a time through the pipes, flushing the pipes with water in between solutions to clean them. Did the technician cause any chemical reactions to occur in the pipes? Show your calculations and justify your answer. 551-534.E55 551-534 Chemistry Comprehensive Exam Number 55 Answer Booklet Secondary 5 September, 2005 Student's Name Group Date Answer Booklet PART A Questions 1 to 14 Blacken the letter that corresponds to your answer. Each question is worth four marks. 1 [A] [B] [C] [D] 2 [A] [B] [C] [D] 3 [A] [B] [C] [D] 4 [A] [B] [C] [D] 5 [A] [B] [C] [D] 6 [A] [B] [C] [D] 7 [A] [B] [C] [D] 8 [A] [B] [C] [D] 9 [A] [B] [C] [D] 10 [A] [B] [C] [D] 11 [A] [B] [C] [D] 12 [A] [B] [C] [D] 13 [A] [B] [C] [D] 14 [A] [B] [C] [D] 551-534.E55 Page 1 Answer Booklet Page 2 PART B Questions 15, 16, 17 and 18 If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 15, 16 and 17 will be corrected. 15 SHOW ALL YOUR WORK Answer: The ratio of the gas pressure in the 2nd container to the initial gas pressure in the 1st container is __________ :1. 4 551-534.E55 3 2 1 0 Answer Booklet 16 Page 3 SHOW ALL YOUR WORK Answer: The volume of water vapour produced is _________________________. 4 551-534.E55 3 2 1 0 Answer Booklet 17 Page 4 SHOW ALL YOUR WORK Answer: The unknown gas is most likely _________________________ because __________________________________________________________________. 4 551-534.E55 3 2 1 0 Answer Booklet 18 Page 5 EXPLANATION a) b) 4 3 2 1 You have just finished Part B. You should have answered three (3) questions. If you have answered all four, draw a line through the question that you do not want to have corrected. 551-534.E55 0 Answer Booklet Page 6 PART C Questions 19, 20, 21 and 22. If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 19, 20 and 21 will be corrected. 19 SHOW ALL YOUR WORK Answer: The specific heat capacity of the unknown metal is ____________________. 4 551-534.E55 3 2 1 0 Answer Booklet 20 Page 7 SHOW ALL YOUR WORK Answer: The H for the neutralization of NaOH solution is ____________________. 4 551-534.E55 3 2 1 0 Answer Booklet 21 Page 8 SHOW ALL YOUR WORK Answer: The H is ____________________. 4 551-534.E55 3 2 1 0 Answer Booklet 22 Page 9 SHOW ALL YOUR WORK 4 3 2 1 You have just finished Part C. You should have answered three (3) questions. If you have answered all four, draw a line through the question that you do not want to have corrected. 551-534.E55 0 Answer Booklet Page 10 PART D Questions 23, 24 and 25. If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 23 and 24 will be corrected. SHOW ALL YOUR WORK Consumption of Nitrogen Concentration (mol/L) of Nitrogen 23 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0 10 20 30 40 50 60 70 Time (min) Answer: The average rate of ammonia production is ____________________. 4 551-534.E55 3 2 1 0 Answer Booklet 24 Page 11 Answer: Substance (s) that could have acted as catalysts (I) ____________________________________________________________________. (II) ____________________________________________________________________. (III) ____________________________________________________________________. 4 25 3 2 1 0 SHOW ALL YOUR WORK Rate calculation: Answer: Answer: Time (min) 0.0 0.2 0.4 0.6 0.8 1.0 I (mol/L) 0.0800 0.0400 0.0200 0.0100 0.0050 0.0025 I2 (mol/L) 0 The average rate of reaction for the production of I2(aq) is _________________. 4 3 2 1 You have just finished Part D. You should have answered two (2) questions. If you have answered all three, draw a line through the question that you do not want to have corrected. 551-534.E55 0 Answer Booklet Page 12 PART E Questions 26, 27, 28 and 29. If you answer all questions in this section, draw a line through the question that you do not want to have corrected. If you do not, questions 26, 27 and 28 will be corrected. 26 SHOW ALL YOUR WORK Answer: The Kc for the reaction at this temperature is ____________________. 4 551-534.E55 3 2 1 0 Answer Booklet 27 Page 13 SHOW ALL YOUR WORK (Show all the work needed to solve the problem: explanations, formulas and calculations.) Answer: ____________________ acid is the stronger of the two. 4 551-534.E55 3 2 1 0 Answer Booklet 28 Page 14 SHOW ALL YOUR WORK a) Diagram b) The standard cell potential is ____________________. c) Method to increase the potential of the given cell. 4 551-534.E55 3 2 1 0 Answer Booklet 29 Page 15 SHOW ALL YOUR WORK Answer: The technician did did not cause a chemical reaction to occur. cause a chemical reaction to occur. because _________________________________________________________ ________________________________________________________________ 4 3 2 1 You have just finished Part E. You should have answered three (3) questions. If you have answered all four, draw a line through the question that you do not want to have corrected. 551-534.E55 0