Chemistry 2 January 2000 Provincial Examination ANSWER KEY / SCORING GUIDE CURRICULUM: Organizers. Reaction Kinetics 2. Dynamic Equilibrium 3. Solubility Equilibria 4. Acids, Bases, and Salts 5. Oxidation Ð Reduction Sub-Organizers A, B, C D, E, F G, H, I J, K, L, M, N, O, P, Q, R S, T, U, V, W Part A: Multiple Choice Q K C CO PLO Q K C CO PLO. B U A 25. A H 4 L3 2. C U A6 26. B U 4 L3, L6 3. D K B3 27. D H 4 L 4. A U B6 28. A U 4 L2 5. B U B9 29. A K 4 M 6. D K C3 30. A K 4 M2 7. A U 2 D3 3. C U 4 M4 8. C K 2 D5 32. D U 4 N3 9. A U 2 D7 33. B U 4 O4 0. C H 2 E2 34. D U 4 P3. B U 2 E2 35. C U 4 P5 2. C K 2 F2 36. D H 4 Q5 3. B U 2 F8 37. D K 4 R4 4. B K 3 G3 38. B U 5 S 5. B U 3 G8 39. B U 5 S 6. C U 3 H2 40. D U 5 S2 7. D H 3 H5 4. B U 5 S6 8. A U 3 I3 42. C U 5 T6 9. C U 3 I4 43. C K 5 U 20. D U 3 I5 44. C U 5 U2, U4 2. A H 3 H5 45. A U 5 U7 22. C K 4 J2 46. C U 5 U9 23. D U 4 J8, N4 47. A K 5 V2 24. A U 4 K, K6 48. D K 5 W2 Multiple Choice = 48 marks 00chk - - February 24, 2000
Part B: Written Response Q B C S CO PLO. U 2 A4 2. 2 H 2 C2 3. 3 U 2 2 E3 4. 4 U 4 2 F6 5. 5 U 2 3 H3 6. 6 U 3 3 I7 7. 7 K 2 4 K0, K 8. 8 U 4 4 M5 9. 9 U 3 4 P2 0. 0 U 2 5 S4. U 4 5 T2 2. 2 U 2 5 W6 Written Response = 32 marks Multiple Choice = 48 (48 questions) Written Response = 32 (2 questions) EXAMINATION TOTAL = 80 marks LEGEND: Q = Question Number K = Keyed Response C = Cognitive Level B = Score Box Number S = Score CO = Curriculum Organizer PLO =Ê Prescribed Learning Outcome 00chk - 2 - February 24, 2000
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.. A student wishes to monitor the rate of the following reaction: CaCO3( s) + 2HCl( aq) CaCl2( aq) + CO2( g) + H2O( l) Identify two different properties that could be used to monitor the rate of the reaction. Describe and explain the changes that would occur. (2Êmarks) Property: Mass 2 mark Change and Explanation: Mass decreases because CO 2( g) leaves the system. 2 mark Property: ph Change and Explanation: ph increases because HCl is consumed. 2 mark 2 mark 00chk - 3 - February 24, 2000
2. Consider the following reaction for the formation of HCl in the presence of light. Cl2 + CHCl3 HCl + CCl4 The following is the proposed reaction mechanism: Step ÊÊÊÊÊÊÊÊÊÊÊ ÊÊÊ Cl2 Cl + Cl Step 2? Step 3 Cl + CCl 3 CCl 4 Determine Step 2 of the reaction mechanism. (2Êmarks) Cl CHCl HCl CCl + + 3 3 2 marks 00chk - 4 - February 24, 2000
3. Consider the following equilibrium: + HInd + H O 2 H3O + Ind ( yellow) ( blue) The system is yellow and turns blue on the addition of NaOH. In terms of the forward and reverse reaction rates, explain why this shift occurs. (2Êmarks) Addition of OH + decreases [ HO 3 ], decreasing the reverse rate. Since the forward rate is greater than the reverse rate, the system shifts to the right. 2 marks 00chk - 5 - February 24, 2000
4. Consider the following equilibrium: 3+ 2+ aq aq aq Fe ( ) + SCN ( ) FeSCN ( ) 3 Initially, 50. 0 ml of 0. 0 M Fe + is added to 30. 0 ml of 0. 20 M SCN. At equilibrium, the concentration of FeSCN 2+ is found to be 0. 050 M. Calculate the K eq for the reaction. (4Êmarks) ÊÊÊÊ 3+ 50. 0 ml [ Fe ]= 0. 0 M = 0. 0625 M 80. 0 ml 30. 0 ml [ SCN ]= 0. 20 M = 0. 0750 M 80. 0 ml 3+ 2+ Fe + SCN FeSCN [] I 0. 0625 0. 0750 0 [ C] 0. 0500 0. 0500 0. 0500 [ E] 0. 025 0. 0250 0. 0500 Ê [ 2+ FeSCN ] K eq = 3+ Fe SCN [ ][ ] = ( 0. 025 )( 0. 0250 ) = 6. 0 0. 0500 2 mark 2 marks 2 marks 00chk - 6 - February 24, 2000
5. a) Write the balanced formula equation for the reaction between Na3PO4( aq) and CuCl2( aq). (Êmark) 2Na PO 3CuCl 6NaCl Cu PO + + ( ) mark 3 4( aq) 2( aq) ( aq) 3 4 2( s) b) Write the net ionic equation for the reaction between Na3PO4( aq) and CuCl2( aq). (Êmark) 2+ 3 aq aq 3 4 2( s) 3 Cu ( ) 2 PO 4 ( ) Cu PO + ( ) mark 00chk - 7 - February 24, 2000
6. A saturated solution of nickel carbonate, NiCO 3, contains 0. 090 g in 2. 0 L of solution. Calculate K sp for NiCO 3. (3Êmarks) 0. 090 g mol [ NiCO3]= = 379. 0 20. L 8. 7 g NiCO 2 3( s) Ni ( aq) + CO 4 + 2 3 4 4 3. 79 0 M 3. 79 0 sp = 2+ 2 [ ][ 3 ] 4 4 = ( 3. 79 0 )( 3. 79 0 ) K Ni CO = 4. 0 7 mol L M mark 2 marks ( Deduct 2 mark for incorrect significant figures. ) 00chk - 8 - February 24, 2000
7. Define the term amphiprotic. Give an example of an ion which is amphiprotic. (2Êmarks) The ability to act as either an acid or a base. For example HPO 4 2. mark mark 8. A 0. 0200 M solution of methylamine, CH NH Calculate the K b for methylamine. 3 2, has a ph =. 40. (4Êmarks) poh = 260. [ OH ]= 25. 0 3 + 3 2 2 3 3 CH NH + H O CH NH + OH [] I 0. 0200 0 0 [ C] 2. 5 0 + 2. 5 0 + 2. 5 0 3 3 3 [ E] 0. 0749 2. 5 0 2. 5 0 [ + CH NH ][ OH ] Kb = 3 3 CH NH [ 3 2] ( 2. 5 0 ) 2. 5 0 = 0. 0749 = 36. 0 4 ( ) 3 3 3 3 mark 2 marks 2 marks ( Deduct 2 mark for incorrect significant figures. ) 00chk - 9 - February 24, 2000
9. A titration was performed by adding 0. 5 M NaOH to a 25. 00 ml sample of H2SO 4. Calculate the HSO 2 4 [ ] from the following data. (3Êmarks) Trial # Trial #2 Trial #3 Initial volume of NaOH ( ml) 400. 7. 05 8. 00 Final volume of NaOH ( ml) 7. 05 28. 00 9. 05 2NaOH + H SO Na SO + 2H O 2 4 2 4 2 vol of NaOH =. 00mL mark mol NaOH 0. 000 L 0. 5mol L. 265 0 mol = ( ) = 3 4 ( ) = mol H SO =. 265 0 mol NaOH 6. 325 0 mol 2 4 2 4 6. 325 0 mol [ HSO 2 4]= 0. 02500 L 3 = 0. 0253 M 2 mark mark 2 mark 00chk - 0 - February 24, 2000
0. a) Indicate in the blank spaces on the following chart whether or not a reaction will occur when the metals are added to aqueous ions. (Êmark) ion metal Pd Rh Pt Pd 2+ reaction no reaction Rh 2+ no reaction no reaction Pt 2+ reaction reaction See table above. b) List the oxidizing agents in order of strongest to weakest. (Êmark) 2+ 2+ 2+ Pt > Pd > Rh 00chk - - February 24, 2000
. Balance the following redox reaction in basicêsolution: (4Êmarks) ( ) Au + Cl + O2 AuCl4 + OH basic ÊÊÊÊÊÊÊÊ ( 4 ) + 2 2 + 2 4 2 4 Au + 4Cl AuCl + 3e ( ) 3 4e + 3H + O OH + H O 4Au + 6Cl + 9H + 3O 4AuCl + 3OH + 3H O + 9OH + 9OH 2 2 4 4Au + 6Cl + 6H O + 3O 4AuCl + 2OH mark for half -reactions mark for balancing charges mark for addition mark for basic OR Decrease 4 2 4 2 Au + Cl + O AuCl + OH Increase 3 Decrease 2 2 4 4Au + Cl + 3O 4AuCl + 6OH Increase 2 2 4 4Au + 6Cl + 3O 4AuCl + 2OH mark for oxidation numbers mark for balancing charges } mark for basic charge 2 2 4 ÊÊÊÊÊÊÊÊ 4Au + 6H O + 6Cl + 3O 4AuCl + 2OH } mark for hydrogen ( H 2 O) 00chk - 2 - February 24, 2000
2. Draw and label a simple electrolytic cell capable of electroplating an inert electrode with silver. (2Êmarks) ( 2 mark) + Ð DC Power Source Anode 2 mark ( ) Ag Cathode 2 mark ( ).0 M Ag + (aq) ( 2 mark) END OF KEY 00chk - 3 - February 24, 2000