Chemistry 12 June 2002 Provincial Examination

Transcription

1 Chemistry 1 June 00 Provincial Examination ANSWER KEY / SCORING GUIDE CURRICULUM: Organizers 1. Reaction Kinetics. Dynamic Equilibrium 3. Solubility Equilibria 4. Acids, Bases, and Salts 5. Oxidation 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 S CO PLO Q K C S CO PLO 1. A U 1 1 A1 5. B K 1 4 K1. C K 1 1 A6 6. A U 4 K8 3. C U 1 1 B5 7. A K 1 4 L 4. B U 1 1 B6 8. D U 4 L1 5. B U 1 1 C5 9. D K 1 4 M 6. C H 1 C4, D 30. A K 1 4 N1 7. A U 1 D3 31. B U 1 4 N3 8. D U 1 E 3. B H 4 O3 9. B H 1 E3 33. B U 1 4 O4 10. D U D7 34. C H 1 4 P1 11. D U 1 F1 35. D U 4 P3 1. B K 1 F 36. D K 1 4 Q 13. C U 1 F4 37. C K 1 4 R1 14. A U F5 38. D K 1 5 S5 15. B K 1 3 G 39. D U 5 S 16. B U 1 3 G8 40. C U 1 5 S6 17. B U 3 H1 41. C U 1 5 S6, U9 18. C U 1 3 H3 4. B K 1 5 U3 19. C U 1 3 H7 43. C H 5 U5 0. B K 1 3 I 44. D U 1 5 T1, U 1. B U 3 I3 45. D U 1 5 U. C U 1 3 I6 46. A H 1 5 U9 3. B K 1 4 J4 47. A U 5 U10 4. C U 1 4 J A U 1 5 W4 Multiple Choice = 60 marks (48 questions) 06chk July 9, 00

2 Part B: Written Response Q B C S CO PLO 1. 1 U 3 1 A3. K 1 B K D U 4 F U 3 3 E, H U 3 3 I U 4 4 J8, K U 4 L U 5 4 M U 3 4 Q U 4 5 T 1. 1 U 3 5 W1, W H 5 S6, U9 Written Response = 40 marks Multiple Choice = 60 (48 questions) Written Response = 40 (13 questions) EXAMINATION TOTAL = 100 marks LEGEND: Q = Question Number K = Keyed Response C = Cognitive Level B = Score Box Number S = Score CO = Curriculum Organizer PLO = Prescribed Learning Outcome 06chk - - July 9, 00

3 PART B: WRITTEN RESPONSE Value: 40 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 calculations, full marks will NOT be given for providing only an answer. 1. Consider the reaction: (3 marks) Al( s) + 6HCl( aq) AlCl3 ( aq) + 3H( g) A g sample of Al reacts completely in excess HCl in s. What is the rate of production of H in mol s? 1mol mol Al = 10. 0g = mol Al 7. 0g mol H rate = = mol Al = mol H = change in moles time mol H s = mol H s 3 3 mol H mol Al ( Deduct 1 mark for incorrect significant figures. ) 3 marks 06chk July 9, 00

4 . Using collision theory, give two reasons why reactions occur more rapidly at a higher temperature. ( marks) There is a greater fraction of collisions with sufficient energy. There are more frequent collisions. marks 06chk July 9, 00

5 3. Chemical reactions tend toward a position of minimum enthalpy and maximum entropy. a) What is meant by the term enthalpy? (1 mark) Enthalpy is a measure of heat content. b) What is meant by the term entropy? (1 mark) Entropy is a measure of randomness. 06chk July 9, 00

6 4. Consider the following: (4 marks) H( g) + Br ( g) HBr( g) Keq = 1. 0 Initially, mol H and mol Br are placed into a L container. What is the HBr [ ] at equilibrium? H + Br HBr [ I ] [ C] x x + x [ E] x x x K eq HBr x [ H ][ Br ] = ( ) x = [ ] ( x) x ( ) = x = [ HBr]= x = M ( ) 1. 0 = marks 06chk July 9, 00

7 5. Consider the following equilibrium and accompanying graph: ( ) + s aq + 3 aq Zn IO3 ( ) Zn ( ) IO ( ) [ IO 3 ] [ Ions] [ Zn + ] marks t 1 t t 3 a) Identify the stress applied at t 1. (1 mark) + More Zn ( aq) has been added. b) Complete the above graph from t 1 to t 3 for the [ IO 3 ]. ( marks) See graph above. 06chk July 9, 00

8 6. Calculate the solubility of SrSO 4 in grams per litre. (3 marks) SrSO + 4() Sr ( ) + SO K Sr SO s aq 4 aq s s s sp = [ ][ ]=. 7 = Solubility = s = ( ) g Solubility in g L = mol L mol = 011. gl M 3 marks 06chk July 9, 00

9 7. The cyanide ion, CN, is a Brønsted-Lowry base. a) Define Brønsted-Lowry base. (1 mark) A Brønsted-Lowry base is a proton acceptor. b) Write the equation representing the reaction of CN with water. ( marks) CN + H O HCN + OH marks c) Identify a conjugate pair in b) above. (1 mark) CN and HCN OR HO and OH 06chk July 9, 00

10 8. Write an equation to show the ionization of water. ( marks) HO + ( ) HO ( aq) + OH ( aq) marks l 3 06chk July 9, 00

11 9. Calculate the ph of M NH 3. (5 marks) NH + H O NH + OH [] I [ C] x + x + x [ E] 150. x x x marks K K b b = [ + NH ][ OH ] 4 = NH [ 3] = x 150. x = x = [ OH ]= poh = 9. ph = ( Deduct 1 mark for incorrect significant figures. ) 3 5 marks 06chk July 9, 00

12 10. Consider the following buffer equilibrium: (3 marks) + HF( aq) + H O ( l) H3O ( aq) + F ( aq) high concentration low concentration high concentration Using Le Châtelier s Principle, explain what happens to the ph of the buffer solution when a small amount of NaOH is added. + NaOH causes [ H 3 O ] to decrease. The equilibrium shifts right. The ph almost returns to the former value. 06chk July 9, 00

13 11. Balance the following redox equation: (4 marks) + Ag + NO3 Ag + NO (acidic) + + ( ) 3 Ag Ag + 3e 3e + 4H + NO3 NO + HO 3Ag + NO + 4H NO + H O + 3Ag marks (1 mark for each half-reaction) for balancing electrons for addition 06chk July 9, 00

14 1. Draw a diagram of an operating electrolytic cell used to extract pure lead from an impure lead sample. Identify the electrolyte and the material used for the anode. (3 marks) 1 mark DC Power Source + Anode (impure lead) 1.0 M Pb(NO 3 ) 06chk July 9, 00

15 13. A sample of copper is placed in HNO 3( aq) and another sample of copper is placed in HCl ( aq). 1 a) In which acid does the copper react? ( mark) Copper reacts in HNO 3( aq). 1 mark b) Calculate E for the reaction that occurs. ( 1 1 marks ) E is +06. volts 1 1 marks END OF KEY 06chk July 9, 00