Insert Personal Education Number (PEN) here. Insert only pre-printed PEN label here. STUDENT INSTRUCTIONS 1. Insert the stickers with your Personal Education Number (PEN) in the allotted spaces above. Under no circumstance is your name or identification, other than your Personal Education Number, to appear on this booklet. 2. Ensure that in addition to this examination booklet, you have a Data Booklet and an Examination Response Form. Follow the directions on the front of the Response Form. 3. Disqualification from the examination will result if you bring books, paper, notes or unauthorized electronic devices into the examination room. 4. When instructed to open this booklet, check the numbering of the pages to ensure that they are numbered in sequence from page one to the last page, which is identified by CHEMISTRY 12 JUNE 2000 COURSE CODE = CH Insert only hand-printed PEN here. ENDÊOFÊEXAMINATION. 5. At the end of the examination, place your Response Form inside the front cover of this booklet and return the booklet and your Response Form to the supervisor. Ministry use only. 2000 Ministry of Education
PART A: MULTIPLE CHOICE Value: 48 marks INSTRUCTIONS: Suggested Time: 70 minutes For each question, select the best answer and record your choice on the Response Form provided. Using an HB pencil, completely fill in the circle that has the letter corresponding to your answer. 1. Which of the following reactions will be slowest at 25 C? A. Cu S CuS ( s) ( s) ( s) B. H ( aq) OH ( aq) H 2 O l C. Pb ( ) 2Cl ( ) PbCl ( ) 2 aq aq 2( s) D. 2NaOCl( aq) 2NaCl( aq) O2( g) 2. Which of the following could be used as the units for rate of a reaction? I. ml s II. III. g min M min A. I only. B. I and II only. C. II and III only. D. I, II and III. - 1 - OVER
3. Consider the following reaction: Zn() s 2HCl( aq) ZnCl2( aq) H2( g) A graph of concentration of HCl vs time could be represented by A. B. [ HCl] [ HCl] time time C. D. [ HCl] [ HCl] time time 4. Consider the following experiments, each involving equal masses of zinc and 10. 0 ml of acid: Experiment I Experiment II Experiment III Zn cube 1.0 M HCl Zn cube 0.5 M HCl Zn powder 1.0 M HCl The rate of reaction in order from fastest to slowest is A. I > II > III B. II > I > III C. III > I > II D. III > II > I - 2 -
5. What happens to the energy of reactant molecules as they approach one another? Potential Energy Kinetic Energy A. increases increases B. increases decreases C. decreases increases D. decreases decreases 6. Consider the following reaction mechanism: The catalyst is A. IO B. HO 2 C. ClO D. ClOH Step 1 ClO H O HClO OH Step 2 I HClO HIO Cl Step 3 Ê HIO OH IO H O 2 2 7. Consider the following equilibrium: 2NOCl( g) 2NO( g) Cl2( g) A flask of fixed volume is initially filled with NOCl( g), NO( g) and Cl 2 ( g). When equilibrium is reached, the pressure has increased. To reach equilibrium, the reaction proceeded to the A. left because Trial Keq was less than Keq B. right because Trial Keq was less than Keq C. left because Trial Keq was greater than Keq D. right because Trial Keq was greater than Keq - 3 - OVER
8. In which of the following do both minimum enthalpy and maximum entropy factors favourêtheêreactants? A. Cl2( g) Cl2( aq) H =25 kj B. C( s) H O 2 ( l) CO( g) H2( g) H =131kJ C. 2CO2( g) 3H2O ( g) C2H5OH( l) 3O2( g) H =1239 kj D. Na2CO3( s) HCl ( aq) 2NaCl( aq) CO2( g) H2O( l) H =28 kj 9. Consider the following equilibrium: H2( g) I 2( g) 2HI( g) Which graph represents what happens when some HI is removed and a new equilibrium is established? A. B. [ HI] [ HI] time time C. D. [ HI ] [ HI ] time time 10. Consider the following equilibrium: What will cause a shift in the equilibrium? A. adding a catalyst B. changing volume C. adding an inert gas D. changing temperature CO( g) H O( g) 2 CO2( g) H2( g) H = 41kJ - 4 -
11. The equilibrium expression for a reaction is The reaction could be 6 [ H ] Keq = 3 2 Bi H S [ ] [ 2 ] 3 A. 6H ( aq) BiS ( s) 2Bi ( aq) 3H2S( g) 3 B. 6H ( aq) Bi2S 3( s) 2Bi ( aq) 3H2S( g) 3 aq ( aq) ( s) ( aq) C. 2Bi ( ) 3H2S Bi2S3 6H 3 D. 2Bi ( aq) 3H2S ( aq) Bi2S3 ( aq) 6H ( aq) 3 12. Consider the following equilibrium: 2 2 ( ) aq aq aq ( l) Co H2O 6 ( ) 4Cl ( ) CoCl4 ( ) 6H2O pink blue ( ) ( ) When the temperature is increased, the solution turns a dark blue. Based on this observation, the reaction is A. exothermic and the K eq has increased. B. exothermic and the K eq has decreased. C. endothermic and the K eq has increased. D. endothermic and the K eq has decreased. 13. Consider the following equilibrium: 2O3 ( g) 3O2( g) Keq = 36 What is the concentration of O 3 when the equilibrium concentration ofê O 2 ÊisÊ 60. 10 2 mol L? A. 24. 10 mol L B. 40. 10 mol L C. 60. 10 mol L D. 90. 10 mol L - 5 - OVER
14. A saturated solution of NaCl contains 36. 5g of solute in 0. 100 L of solution. The solubility of the compound is A. 0. 062 M B. 1. 60 M C. 365. M D. 624. M 15. Calculate the Li A. 030. M B. 060. M C. 15. M D. 30. M [ ] in 200. 0 1. 5 2 4 ml of M Li SO. 16. When equal volumes of 0. 20M RbCl and 020. M SrS are combined, A. no precipitate forms. B. a precipitate of Rb 2 S only forms. C. a precipitate of SrCl 2 only forms. D. precipitates of both Rb 2 S and SrCl 2 form. 17. A solution contains both Ag and Mg 2 ions. During selective precipitation, these ions are removed one at a time by adding A. I followed by OH B. OH followed by S 2 C. SO 4 2 followed by Cl D. NO 3 followed by PO 4 3-6 -
18. The K sp expression for a saturated solution of Mg( OH) 2 is A. K [ Mg ][ OH ] sp = [ Mg( OH) 2] 2 2 sp = [ ][ ] 2 2 B. K Mg OH C. Ksp = 2 [ Mg ][ OH ] sp = [ ][ ] 2 2 D. K Mg 2 OH 19. Consider the following saturated solutions: CuSO4, BaSO4, CaSO4 The order of cation concentration, from highest to lowest, is [ 2 ] > [ 2 ] > [ 2 ] [ 2 ] > [ 2 ] > [ 2 ] [ 2 ] > [ 2 ] > [ 2 ] [ 2 ] > [ 2 ] > [ 2 ] A. Ba Ca Cu B. Ca Cu Ba C. Cu Ca Ba D. Cu Ba Ca 20. When 1. 0 10 3 moles of CuCl2 s are added toê1 0 10 10. Lof. 3 MIO 3, the A. Trial K > K and a precipitate forms. sp sp B. Trial K < K and a precipitate forms. sp sp C. Trial K > K and no precipitate forms. sp sp D. Trial K < K and no precipitate forms. sp sp ( ) 21. The conjugate base of HPO 2 4 is A. OH B. PO 4 3 C. HPO 3 4 D. HPO 4 2-7 - OVER
22. Aqua regia is a concentrated aqueous solution of HCl and HNO 3. The strongest acid in aquaêregia is A. HCl B. HO 2 C. HO 3 D. HNO 3 23. The predominant acid-base reaction between HO 2 2 and H O 2 is 2 2 2 3 2 2 2 2 2 2 2 2 3 2 A. HO HO OH H B. HO HO 2HO O C. HO HO HO OH 2 2 2 3 2 D. HO HO HO HO 24. Which of the following reactions favours the formation of products? 2 2 A. HNO F HF NO 2 3 3 3 3 B. H CO IO HIO HCO 2 4 2 4 2 4 3 C. NH C O HC O NH D. HCN HCOO HCOOH CN [ 3 ]? 25. Which of the following 1. 0M solutions will have the lowest HO A. HS 2 B. HNO 2 C. HCO 2 3 D. CH3COOH - 8 -
26. In a solution of 010. M NaCN, the order of ion concentration, from highest to lowest, is [ ]> [ ]> [ ]> [ 3 ] [ ]> [ ]> [ ]> [ 3 ] [ 3 ]> [ ]> [ ]> [ ] [ ]> [ ]> [ ]> [ 3 ] A. Na OH CN H O B. Na CN OH H O C. H O OH CN Na D. OH Na CN H O 27. What will cause the value of K w to change? A. adding OH B. adding a catalyst C. decreasing the ph D. increasing the temperature 28. What is the concentration of Sr( OH) 2 in a solution with a ph = 11. 00? A. 20. 10 11 B. 10. 10 11 C. 50. 10 4 D. 10. 10 3 M M M M 29. The K a expression for HTe is [ HTe ] [ OH] A. Ka = 2 HTe [ ] [ 2 Te ][ H O ] B. Ka = 3 HTe [ ] [ HTe ] [ H O ] C. Ka = 3 HTe [ 2 ] [ HTe ][ OH ] D. Ka = 2 Te [ ] - 9 - OVER
30. When comparing 1. 0M solutions of bases, the base with the lowest [ OH ] is the A. weakest base and it has the largest K b value. B. strongest base and it has the largest K b value. C. weakest base and it has the smallest K b value. D. strongest base and it has the smallest K b value. 31. The value of K b for HC O 2 4 is A. 17. 10 13 B. 16. 10 10 C. 64. 10 5 D. 59. 10 2 32. Which of the following applies at the transition point for all indicators, HInd? [ ]= [ ] A. HInd Ind [ ] = [ 3 ] [ 3 ]= [ ] B. Ind H O C. HO OH [ ]= [ 3 ] D. HInd H O 33. Identify the indicator that has a Ka of 16. 10 7 A. methyl red B. thymol blue C. phenolphthalein D. bromthymol blue? - 10 -
34. Which of the following acid solutions would require the smallest volume to completely neutralize 10. 00 ml of 0. 100 M NaOH? A. 0. 100 M HCl B. 0. 100 M H3PO4 C. 0. 100 M H2C2O4 D. 0. 100 M CH3COOH 35. What is the ph of the solution formed when 0. 040 mol NaOH ( s) is added to 1. 00 L of 0. 050 M HCl? A. 130. B. 140. C. 200. D. 700. 36. Which of the following titrations will have an equivalence point with a ph less than 700.? A. H2SO4 with NH3 B. HNO3 with LiOH C. H3PO4 with KOH D. HCOOH with NaOH 37. Which of the following graphs describes the relationship between ph of a buffer solution and a volume of HCl added to the buffer? A. B. ph ph Volume of HCl added Volume of HCl added C. D. ph ph Volume of HCl added - 11 - Volume of HCl added OVER
38. A substance that is reduced during a redox reaction A. loses mass. B. is the anode. C. is the reducing agent. D. is the oxidizing agent. 39. The oxidation number of As in H AsO 4 2 7 is A. 4 B. 5 C. 9 D. 10 40. In a reaction, the oxidation number of Cr decreases by 3. This indicates that Cr is A. reduced. B. oxidized. C. neutralized. D. a reducing agent. 41. Consider the following redox reaction: 2 5 2 7 2 3 2 C H OH 2Cr O 16H 2CO 4Cr 11H O Each carbon atom loses A. 2 electrons B. 4 electrons C. 6 electrons D. 12 electrons 2-12 -
42. In which of the following 1. 0M solutions will both ions react spontaneously with tin? 2 A. Ag and Cu 2 2 B. Ni and Cu 2 2 C. Zn and Ni 2 2 D. Mg and Zn 43. Consider the following half-reaction: Bi2O4 BiO ( acidic ) The balanced equation for this half-reaction is 2 4 2 2 4 8 6 2 4 2 2 4 4 2 2 2 2 2 4 4 3 2 2 2 A. Bi O 6H 5e BiO 3H O B. Bi O H e BiO H O C. Bi O H e BiO H O D. Bi O H e BiO H O 44. To determine the concentration of Fe ( aq) standardêsolutionêof 2 by a redox titration, we could use an acidified A. Sn 2 B. Pb 2 C. HCl D. HO 2 2 45. Consider the following redox reactions: 2 2Ag Cd 2Ag Cd E = 1. 20V 2 3 What is the E for Nb 3e Nb? A. 1. 90V B. 1. 10V C. 0. 50V D. 0. 40V 3Cd 2Nb 2Nb 3Cd E = 0. 70V 3-13 - OVER
46. Consider the overall reaction for the rechargeable nickel-cadmium battery: Cd NiO 2H O Cd OH Ni OH ( ) ( ) 2 2 2 2 Which of the following occurs at the cathode as the reaction proceeds? A. Cd loses 2e and Cd( OH) 2 forms B. Cd gains 2e and Cd( OH) 2 forms C. NiO 2 loses 2e and Ni( OH) 2 forms D. NiO 2 gains 2e and Ni( OH) 2 forms 47. Consider the following diagram of a piece of iron, cathodically protected by magnesium: Water containing dissolved oxygen Iron Magnesium What is happening during this process? A. Iron acts as the anode and water is oxidized. B. Iron acts as the cathode and oxygen is reduced. C. Magnesium acts as the anode and iron is oxidized. D. Magnesium acts as the cathode and iron is reduced. - 14 -
48. Consider the following operating cell: Ð DC Power Source Electrode #1 Electrode #2 Gas Produced 1.0 M KI (aq) Which of the following describes the cell above? Electrode #1 Electrode #2 Gas Produced A. anode cathode H 2( g) B. anode cathode O 2( g) C. cathode anode H 2( g) D. cathode anode O 2( g) This is the end of the multiple-choice section. Answer the remaining questions directly in this examination booklet. - 15 - OVER
PART B: WRITTEN RESPONSE Value: 32 marks INSTRUCTIONS: Suggested Time: 50 minutes You will be expected to communicate your knowledge and understanding of chemical principles in a clear and logical manner. Your steps and assumptions leading to a solution must be written in the spaces below the questions. Answers must include units where appropriate and be given to the correct number of significant figures. For questions involving calculation, full marks will NOT be given for providing only an answer. 1. a) Complete the steps in the following mechanism. (1 1 2 Êmarks) Step 1 NO Pt Step 2 NOPt NO Step 3 Ê Ê OPt 2 O2 Pt Overall 2NO N2 O2 b) Define the term reaction intermediate and give an example from the completed mechanism above. (1 1 2 Êmarks) Definition: Example: - 16 -
2. Consider the observations for the following equilibrium: NO ( g) 2NO ( g) 2 4 2 ( colourless) ( brown) Trial Temperature C Colour I. 10 light brown II. 50 dark brown a) Sketch the potential energy curve on the graph below for this equilibrium. (1Êmark) PE progress of the reaction b) Explain the colour change using Le Ch telierõs Principle. (1Êmark) c) Other than changing temperature, what could be done to cause a shift to the left? (1Êmark) - 17 - OVER
3. Consider the data obtained for the following equilibrium: 3 2 aq aq aq Fe ( ) SCN ( ) FeSCN ( ) [ Fe 3 ] [ SCN ] [ FeSCN 2 ] Experiment 1 391. 10 2 Experiment 2 627. 10 3 802. 10 5 365. 10 4 922. 10 4? Calculate the [ FeSCN 2 ] in experiment #2. (3Êmarks) - 18 -
( ) is combined with 4. At 25 C, will a precipitate form when 25. 0 ml of 0. 010 M Pb NO3 2 75. 0 ml of 0. 010 M NaI? Support your answer with calculations. (3Êmarks) - 19 - OVER
5. When HCl is added to a saturated solution of CuC O 2 4, some precipitate dissolves. However, when HCl is added to a saturated solution of PbCl 2, additional precipitate forms. HCl HCl CuC 2 O 4 PbCl 2 Explain these observations. Support your explanation with chemical equations. (3Êmarks) - 20 -
6. A 0. 100 M solution of an unknown weak acid, HX, has a ph = 1. 414. What is the Ka for HX? (4Êmarks) - 21 - OVER
7. Consider the salt ammonium acetate, NH4CH3 COO. a) Write the equation for the dissociation of NH CH COO 4 3. (1Êmark) b) Write equations for the hydrolysis reactions which occur. (2Êmarks) c) Explain why a solution of NH4CH3 COO has a ph = 700.. Support your answer with calculations. (2Êmarks) - 22 -
8. The metals Rh, Ti, Cr and Pd are individually placed in 1. 0Msolutions 2 2 2 2 of Ê Rh, Ti, Cr and Pd and the cell voltages of the spontaneous reactions are determined. METAL ION Rh 2 Ti 2 Pd 2 Cr 2 Rh no reaction 0.35 V no reaction Ti 2.23 V 2.58 V? Pd no reaction no reaction no reaction Cr 1.51V no reaction 1.86 V a) Arrange the metals in order of increasing strength as reducing agents. (2Êmarks) weakest reducing agent,,, strongest reducing agent 2 b) Determine the cell voltage for Ti in a 10. M solution of Cr. (2Êmarks) - 23 - OVER
9. Consider the following reactions for a fuel cell : cathode: O 2H O 4e 4OH 2( g) 2 ( l) anode:? overall: 2H O 2H O ( aq) 2( g) 2( g) 2 ( l) a) Write the reaction at the anode. (1Êmark) b) Discuss the advantage of a fuel-cell powered vehicle over an internal combustion powered vehicle by comparing the products formed. (1Êmark) - 24 -
10. Draw and label an electrochemical cell using a copper anode and having an E value > 100. V. (2Êmarks) END OF EXAMINATION - 25 -