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Chemistry Appendixes Appendix A-F_Chem20 780 11/1/06 10:36 AM Page 780 Appendix A-F_Chem20 11/1/06 10:36 AM Page 781 contents Chemistry Appendixes A. Numerical Answers to Questions 783 B. Scientific Problem Solving 790 B.1 B.2 B.3 B.4 Scientific Problem-Solving Model Investigation Report Outline Sample Investigation Report The Nature of Scientific Research C. Technological Problem Solving C.1 C.2 C.3 C.4 Technological Problem-Solving Model Investigation Reports Laboratory Equipment Laboratory Processes D. STS Problem Solving D.1 STS Decision-Making Model D.2 Types of Reports E. Safety Knowledge and Skills 790 790 793 794 796 796 796 797 802 806 806 806 807 E.1 Laboratory Safety E.2 Safety Symbols and Information E.3 Waste Disposal 807 809 810 F. Communication Skills 811 F.1 F.2 F.3 F.4 F.5 Scientific Language SI Symbols and Conventions Quantitative Descriptions and Rules Tables and Graphs Problem-Solving Methods 811 811 813 815 816 G. Review of Chemistry 20 817 H. Diploma Exam Preparation 823 781 Appendix A-F_Chem20 11/1/06 10:36 AM Page 782 I. Data Tables Thermodynamic Properties of Selected Elements Thermodynamic Properties of Selected Compounds Miscellaneous Specific and Volumetric Heat Capacities Standard Molar Enthalpies of Formation Relative Strengths of Oxidizing and Reducing Agents Relative Strengths of Aqueous Acids and Bases J. Common Chemicals 782 826 826 826 826 827 828 829 830 NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 783 Appendix A NUMERICAL ANSWERS TO QUESTIONS Chemistry Review Unit Unit 2 Are You Ready? (pp. 4–5) Chapter 4 2. (b) 4.2 g Section 4.1 Lab Exercise 4.1 (p. 148) Chapter 1 Section 1.4 Section 1.4 Questions (p. 26) 11. 1, 2, 3, 3–, 2–, 1– Chapter 2 Section 2.4 Section 2.4 Questions (p. 57) 1. (a) 18.02 g/mol (b) 44.01 g/mol (c) 58.44 g/mol (d) 342.34 g/mol (e) 252.10 g/mol 2. (a) 4 sig.dig. (b) 2 sig.dig. (c) 2 sig.dig. (d) 3 sig.dig. (e) 1 sig.dig. (f) 4 sig.dig. 3. (a) 0.117 mol (b) 24 g (c) 50.0 mmol (d) 12.49 g 4. (a) 1.72 103 g or 1.72 kg (b) 50.0 L (c) 1.55 mol/L (d) 13.6 mL (e) 2% (f) 3.94 kJ 5. (a) 0.907 mol (b) 8.56 mol (c) 29.21 mol (d) 1.80 mmol (e) 2.45 mol 6. (a) 71.9 g (b) 8.96 g (c) 1.03 g (d) 1.49 Mg (e) 0.10 kg 7. (a) 2.02 g, 70.90 g, 92.92 g (b) 64.10 g, 96.00 g, 88.02 g, 72.08 g NEL 1, 5, 3, 2, 4 Practice (p. 150) 2. (a) 0.952 atm, 724 mm Hg (b) 110 kPa, 1.09 atm (c) 253 kPa, 1.90 103 mm Hg Practice (p. 152) 6. 263 kPa 7. 137 L 8. (b) 0.17 L. 9. 149 kPa. Practice (p. 154) 11.–273 °C, 0 K 12. (a) T (0 273) K 273 K (b) T (100 272) K 373 K (c) T (30 273) K 243 K (d) T (25 273) K 298 K 13. (a) t (0 273) °C –273 °C (b) t (100 273) °C 173 °C (c) t (300 273) °C 27 °C (d) t (373 273) °C 100 °C Practice (p. 156) 14. (a) 16 mL 15. 0.12 L 16. 26% 17. 79 °C Practice (p. 159) 20. 87.6 kPa 21. 7.9 L 23. 25 °C Section 4.1 Questions (pp. 161–162) 1. (a) 8.87 kPa, 66.5 mm Hg (b) 0.247 atm, 188 mm Hg (c) 112 kPa, 1.11 atm 2. (a) 298 K (b) 238 K (c) 39 °C (d) 65 °C 3. 384 mm Hg 4. 0.16 L 5. (a) 62 L (b) 2.3 times larger 6. 231 °C 11. (a) 3.82:1 15. (a) 2.8 L Section 4.2 Practice (p. 166) 5. 25.0 L 6. 0.60 L 7. (a) 1.5 ML Section 4.2 Questions (p. 168) 4. (a) 124 kL (b) 124 kL 5. (a) oxygen, 125 L; nitrogen monoxide, 100 L; water vapour, 150 L (b) 375 L (c) 33.3 L Section 4.3 Section 4.3 Questions (p. 171) 5. 186 L 6. 2.0 mmol 7. 50.4 L 8. 0.18 mol 9. 73 mL 10. 9.80 L 11. 0.539 ML (or 539 kL) 12. 0.727 g 13. 2.58 g 14. (a) 1.8 g/L Section 4.4 Practice (pp. 174–175) 3. 1.6 MPa 4. 41.0 mmol 5. 34 kL or 34 m3 Lab Exercise 4.B (p. 175) R, 8.48 kPa⋅L/(mol⋅K) Section 4.4 Questions (p. 176) 5. 5.6 mol 6. 225 °C atm•L 8. 0.0821 mol•K 9. (a) 34.0 g/mol 10. 22.4 L, 24.8 L 11. (a) 1.1 g/L (d) 1.74 g/L Unit 2 Review (pp. 180–183) 18. (a) 273 K (b) 294 K (c) 0 K Numerical Answers to Questions 783 A Appendix A-F_Chem20 11/1/06 10:36 AM 19. (a) 0.405 MPa 20. 21. 26. 27. 28. 29. 31. 32. 33. 35. 36. 37. 38. 39. (b) 102 kPa (c) 45.6 MPa (a) 0.21 mol (b) 0.924 mol (a) 12.4 kL (b) 1.4 ML 8.23 L 14 °C 0.33 mol 4.73 L (a) 1.78 atm (b) 196 kPa 317 °C (a) 302 kPa (b) 30.7 kg (a) ammonia, 1.00 L; oxygen, 1.25 L (a) 50 mL methane, 0.647 g/L; nitrogen, 1.13 g/L (a) 150 mL (b) 7.5 mmol (c) 167 mL Unit 3 Chapter 5 Section 5.3 Practice (pp. 205–206) 2. 7.5% V/V 3. 32% W/V 4. 4.9% W/W 5. 5.4 ppm 6. 1.8 mol/L Practice (p. 208) 7. 350 mL 8. 7.5 kg 9. 4.1 mol 10. 0.25 mol 11. 403 mL 12. 54 mL Practice (p. 210) 13. 15.0 g 14. 0.16 kg (a) 355 mg (b) 8.07 mmol/L (a) 7.83% W/V (b) 1.34 mol/L Practice (p. 212) 17. (a) [Na(aq)] 0.82 mol/L; [S2(aq)] 0.41 mol/L 784 Appendix A Page 784 (b) [Sr2(aq)] 1.2 mol/L; [NO3(aq)] 2.4 mol/L (c) [NH4 (aq)] 0.39 mol/L; [PO43(aq)] 0.13 mol/L 18. [Fe (aq)] 49.6 mol/L; 3 [Cl(aq)] 149 mmol/L 19. (a) 11.1 g (b) 18.5 g Section 5.3 Questions (p. 214) 3. (a) 5% W/V 4. 20 ppm 5. (a) 0.32 mol/L (b) [NH4(aq)] 0.64 mol/L; [CO32(aq)] 0.32 mol/L 6. 79.0 g 8. (a) 1.30 g (b) initial volume 10.0 mL Chapter 5 Review (pp. 231–233) 22. 51 g, 150 g, 250 g 23. 0.3 L 24. (a) 0.70 mol/L (b) 0.125 mol/L (c) 2.0 mol/L (d) 0.66 mmol/L 25. 12.6 g 26. 42.8 mL 27. 6.6 g 28. (a) 56 mg 32. 28.1 mL 34. (a) [K(aq)] 0.14 mol/L; [NO3(aq)] 0.14 mol/L 7. 11 mg 8. 4.3 mol/L 9. (a) 0.58 g (b) 0.75 g (b) [Ca2(aq)] 0.14 mol/L; [Cl(aq)] 0.28 mol/L (c) [NH4(aq)] 0.42 mol/L; [PO43(aq)] 0.14 mol/L (c) 1.1 g 10. 0.20 L Chapter 6 11. (a) 0.143 mol/L Section 6.2 (b) 0.429 mol/L Practice (p. 239) 1. (a) 107 mol/L 12. 2.3 g 9 17. (a) 1:10 (b) 1011 mol/L (b) 0.001 ppm (c) 102 mol/L 1 g solute (c) kg solution (d) 104 mol/L (d) 30 µg/kg Section 5.4 Practice (p. 216) 1. 3.10 g 2. 200 g 4. (a) 33.2 g 5. (a) 5.93 g Practice (pp. 218–219) 6. 42% 7. 22.5 mL 8. (a) 0.250 mmol/L (b) 0.399 mg Section 5.4 Questions (p. 219) 3. 3.27 g 4. 43.5 L (e) 1014 mol/L 2. (a) 3 (b) 5 (c) 7 (d) 10 3. 100 Practice (p. 242) 5. (a) 2.68 (b) 5.0 (c) 6.602 (d) 8.14 6. (a) 5 1012 mol/L (b) 2.2 103 mol/L (c) 6 105 mol/L (d) 1.76 1014 mol/L Practice (p. 243) 9. 0.65 5. 6.85 g/L 10. 1.6 107 mol/L 6. 1.51 g Section 6.2 Questions (p. 244) 7. 25.0 mL 6. 5.00 NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 785 Appendix A 8. increase of 3 pH units 9. (a) 1.00 (b) 14.80 (b) 5.10 39. 2.82 g 49. 0.012 mol/L Section 6.3 51. 0 Lab Exercise 6.B (p. 247) 56. (b) 4 103 mol/L Section 6.5 Practice (p. 255) 4. (a) 0.15 mol/L (b) 0.82 Chapter 6 Review (pp. 263–264) 14. (a) 2.74 1012 mol/L (b) 3 104 mol/L 15. 10× 17. (a) between 5.4 and 6.0 (b) 1 106 mol/L to 4 106 mol/L Unit 3 Review (pp. 265–269) 22. (a) 75.0 ppm (b) 1.87 mmol/L 23. 1.2 L 24. (a) 0.23 mol/L (b) 20 mmol (c) 0.103 L (d) 0.155 mol/L (e) 1.21 g 25. 16.9 mg/L 26. (a) 14 L 27. (a) [Na(aq)] 4.48 mol/L; [S2(aq)] 2.24 mol/L (b) [Fe2(aq)] 0.44 mol/L; [NO3(aq)] 0.88 mol/L (c) [K(aq)] 0.525 mol/L; [PO43(aq)] 0.175 mol/L (d) [Co3(aq)] 0.0862 mol/L; [SO42(aq)] 0.129 mol/L 30. (a) 2.12 (b) 2.60 31. (a) 2.74 1012 mol/L (b) 3 10–4 mol/L 35. (a) 103 mol/L (fruit juice); 1012 mol/L (cleaning solution) (b) 109:1 37. (a) 6.3 NEL Practice (p. 302) 1. 0.537 mol/L 2. 375 mL 3. 90.0 mL Lab Exercise 7.C (p. 302) 4.4 - 4.8; 6.0 - 6.6; 3.2 - 3.8 Section 6.3 Questions (p. 247) 2. (a) < 4.8 (b) > 12.0 (c) > 5.4 (d) between 6.0 and 7.6 3. (a) between 5.4 and 6.0 (b) 1 106 mol/L Section 7.4 Unit 4 Are You Ready? (pp. 272–273) 3. (a) 2 105 mol/L 4. (NH4)3PO4(s), 0.2951 mol; CH3COOH(l), 3.5 g 5. NaOH(aq), 1.10 mol; HCl(aq), 0.00345 L; Na2SO4(aq), 1.13 mol/L 6. CH4(g), 0.611; UF6(g), 0.120; CO2(g), 2.48 103 L; Ar(g) 0.161 Chapter 7 Section 7.2 Practice (p. 290) 9. 12 g 10. 66.2 g 11. 36.3 g 12. 6.11 g 13. 0.307 g 14. 2.32 g Lab Exercise 7.A (p. 291) 6.68 g Lab Exercise 7.B (p. 293) 9.12 g Section 7.2 Questions (p. 293) 6. 3.88 g 8. (a) 2.93 g (b) 95.9% 10. (a) 11 g (b) 91% Section 7.3 Practice (p. 296) 1. 16 L 2. 60.1 kL 3. 150 L Section 7.3 Questions (p. 298–299) 2. 6.0 L 3. 2.62 ML 4. 232 kg 5. 0.21 kL, or 0.21 m3 6. 0.77 L 7. 1.94 kg 8. 0.57 L 210 mg; 0.20 g Lab Exercise 7.D (p. 303) 0.351 mol/L Section 7.4 Questions (p. 303) 1. 0.35 L 2. 17.8 mol/L 3. 23.9 mmol/L 4. (b) 624 mg or 0.624 g (c) 98.0% 5. 639 g Chapter 7 Review (p. 309–311) 20. (a) NaHCO3(s), 2.4 mol; Na2CO3(s), 1.2 mol; CO2(g), 1.2 mol; H2O(l), 1.2 mol (b) 0.631 kg 21. 46 mL 2.93 g 23. (a) 95.0% 26. (a) 14.7 g (b) 10.7 g 28. 2.08 kg 29. 1.91 kg 30. 1.17 kg 33. 0.668 mol/L Chapter 8 Section 8.2 Lab Exercise 8.A (p. 317) 5.40 g Section 8.2 Questions (p. 319) 1. 97 g sodium sulfate 2. 0.135 mol/L 3. 0.210 g predicted; 0.20 g obtained; 5% 4. 0.351 mol/L Section 8.3 Practice (p. 321) 1. (a) 1.1 g to 1.2 g 2. 33.6 mL Practice (p. 324) 3. (a) 5.0 mol (b) 0.55 mol (c) 0.26 mol (d) 5.46 mmol Numerical Answers to Questions 785 A Appendix A-F_Chem20 11/1/06 10:36 AM 4. (a) 6.25 g (b) 2.86 g (c) 36.mg (d) 4.2 kg Section 8.3 Questions (p. 327) 4. 3 g 5. (a) 2.77 g (b) 3.89 g 6. 97.9% 7. (b) 2.3 g BaCl2 (c) 8.4 g 0.036 mol 8. (b) 0.053 mol Zn (c) 83% 9. (b) 125 mL (c) 138 mL Section 8.4 Page 786 27. 1.2 102 g 31. 13.0 mL 33. 2.93 g 34. (b) 1.07 g 36. 1.22 g predicted; 1.27 g obtained; 4.5% Unit 5 Chapter 10 Chapter 8 Review (pp. 346–348) 13. (a) 0.075 mol lead (II) nitrate (b) 1 mol propane (c) 0.50 mol zinc (d) 50 mmol sulfuric acid 14. 79.7% 15. 50 mL 16. 3.0 g 17. (a) 20 mL, 20 mL, 20 mL, 20 mL (b) 7, 9, 5, 7 19. 0.0212 mol/L Unit 4 Review (pp. 349–51) 24. (a) 106% 25. 699 kg 26. (a) 0.20 mol Zn(s) (b) 5.0 mmol Cl2(aq) (c) 0.05 mol NaOH(aq) 786 Appendix A (b) 2.07 MJ 5. 0.242 MJ 6. 64 kJ/mol 7. 26 kJ/mol Practice (p. 431) Section 11.3 15. (a) 18 mL Section 11.3 Questions (p. 501) (b) 18 mL (c) 18 mL 40. (a) 0.46 kL Section 8.5 Questions (p. 339) 8. (a) 1.27 g 9. 0.140 mol/L (c) 4% 3. (a) 7.8 MJ Section 10.3 Section 8.5 Practice (p. 336) 2. (b) 7 (b) 2.2 kJ 11. 41.1 kJ/mol Chapter 10 Review (pp. 466-467) Analysis (a) 3.00 105 mol (b) 2.22 106 mol (c) 2.778 105 mol (d) 0.0139 mol/L; BAC 0.064 g/100 mL 2. (a) 2.1 kJ 4. 1.54 g Section 8.4 Questions (p. 332) 1. [NH3] 20.7 mol/L 4. 0.660 mmol Web Activity: Web Quest—Blood Alcohol Content (p. 333) Section 11.2 Questions (p. 494) 20. 36.8% Unit 5 Review (pp. 119–120 ) (b) 4.6 103 km 42. 78.2% 48. 96.3%; 94.8% 53. 1990 CO2: 96.3%; 2001 CO: 94.8% Unit 6 3. (a) 241.8 kJ/mol (b) 318.0 kJ/mol (c) 81.6 kJ/mol (d) 372.8 kJ/mol 4. (a) 114 kJ (c) 114 kJ/mol (d) 57 kJ/mol Section 11.4 Practice in 11.4 (pp. 504–505) 1. 851.5 kJ 2. 131.3 kJ 3. 524.8 kJ 4. 205.7 kJ Chapter 11 Lab Exercise 11.B (p. 506) Section 11.1 3488.7 kJ/mol; -3.35 MJ/mol; 4.0% Case Study, (p. 482) Lab Exercise 11.C (p. 506) 2. 77.8 kJ Section 11.1 Questions (pp. 483–484) 1. (a) respectively, for 2003: 8.22%, 35.21%, 43.55%, 3.99%, 9.04% 2. (a) respectively, for 2003: 58%, 63%, 56%, 42%, 8% 3. respectively, for 2003: 30.4%, 29.5%, 2.8%, 17.7%, 1.7%, 17.9% Section 11.2 Practice (p. 487) 205.9 kJ Section 11.4 Questions (pp. 508–509) 1. 69.5 kJ 2. (a) 136.4 kJ (b) 44.2 kJ 3. 121.2 kJ/mol 7. 2.39 MJ 8. 2.20 MJ 9. 250.1 kJ/mol 10. 492 kJ 6. 84 kJ 11. 21.8 kJ 7. 0.39 MJ Section 11.5 8. 67.7% Lab Exercise 11.D (p. 513) Practice (p. 492) 725.9 kJ/mol; 598 kJ/mol; 17.6% 12. 5.00 MJ Section 11.5 Questions (pp. 514–515) 13. 612 kJ 2. (a) 205.9 kJ Lab Exercise 11.A (p. 492) (b) 41.2 kJ 54.6 kJ/mol (c) 91.8 kJ NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 787 Appendix A 3. (a) 225.5 kJ/mol (f) 38 kJ (b) 58.1 kJ/mol (g) 38 kJ (c) 23.6 kJ/mol (h) 38 kJ 5. –4; –2; 0; 2; 4 Section 13.3 Questions (p. 595) 4. (a) C 2; O –2 4. (a) 145.6 kJ/mol Unit 6 Review (pp. 547–551) (b) O 0 5. (a) 349.6 kJ/mol 19. (a) 176.2 kJ (c) N 3; H 1; Cl 1 20. (b) 128.7 kJ (d) H 1; P 5; O 2 6. (a) 562.0 kJ 8. (a) 179.2 kJ (b) 64.5 kJ (c) 114.7 kJ (d) 114.7 kJ 9. –114.7 kJ 10. 198.7 kJ/mol 12. 2803.1 kJ/mol; 2.80 MJ/mol; 0.143% Chapter 11 Review (pp. 519–521) 17. (a) 44 kJ (b) 36 kJ/g 18. (a) 75.1 kJ (b) 75.1 kJ (c) 2.87 MJ/mol 19. 44.4 kJ/mol 20. (a) 21.8 MJ (b) 393 g (c) 234 L (c) 4.02 MJ 21. (a) 1164.8 kJ (b) 388.3 kJ/mol (c) 1.51 GJ 22. (a) 136.4 kJ (b) 311.4 kJ 23. (a) 23.5 kJ 28. (a) 98.0 kJ/mol 29. 890.5 kJ/mol; 1560.4 kJ/mol; 2219.9 kJ/mol 25. 69 kJ 26. (a) 401.0 kJ/mol 27. (a) 27.2 kJ (b) 2.3 kJ 28. 426 kJ; 110 kJ; 602 kJ 29. (a) 2 219.9 kJ/mol (b) 2 043.9 kJ/mol (c) 1 564.2 kJ/mol Chapter 12 Section 12.3 Questions (p. 70) (f) Na 1; P 5; O 2 8 5. (a) 3 Section 13.4 Lab Exercise 13.C (p. 598) 0.258 mol/L Practice (p. 598) 3. 8.5 L 4. 0.325 mol/L 5. 11.4 mmol/L 55.48 MJ/kg; 51.88 MJ/kg; 50.33 MJ/kg Lab Exercise 13.D (p. 599) 62.31 mol/kg; 66.49 mol/kg; 68.01 mol/kg Investigation 13.4 (p. 603) 1.31 mol/L 30. (b) 134.6 kJ Analysis: 2.94% 31. (a) 1366.8 kJ Section 13.4 Questions (p. 600) 36. 25.6 kJ/mol 22. 1 256.2 kJ 24. 107.4 kJ (e) Na 1; S 2; O 2 4. 1.92 mol/L 5. Analysis: 74.9 mmol/L Evaluation: 6.4% Unit 7 6. 25.9 mmol/L Chapter 13 7. 29.8 mmol/L Section 13.3 Chapter 13 Review (pp. 606–609) Practice (p. 585) 29. 4.8 g 1. (a) 4 (b) 7 30. 56.3 mmol/L 33. Analysis: –33 ºC (c) 6 (d) 6 Chapter 14 (e) –1 Section 14.1 (f) –1 Practice (p. 614) 2. (a) 1 3. 6 (b) 2 Section 14.2 (b) 95 kJ (c) 4 Practice (p. 631) (c) 35 kJ (d) –3 11. (a) 0.77 V (d) 35 kJ (e) –2 (b) 0.45 V (f) 5 (c) 1.23 V 3. (a) 60 kJ 7. 5 kJ/mol; 6 kJ/mol; 11% Chapter 12 Review (pp. 545–546) (g) 0 Practice (p. 633) 16. (a) 52 kJ (h) –3 12. (a) 0.47 V NEL (b) 90 kJ 3. (a) 0 (b) 0.50 V (c) 22 kJ (b) 0 (c) 0.77 V (d) 60 kJ (c) 4 13. 0.34 V (e) 38 kJ (d) 2 14. Cu: 3.38 V; Zn: 2.28 V Numerical Answers to Questions 787 A Appendix A-F_Chem20 11/1/06 10:36 AM Lab Exercise 14.A (p. 633) Cr2O72–: 1.23 V; Pd2: 0.95 V; Tl: 0.34 V; Ti2: 1.63 V Section 14.2 Questions (pp. 637–638) 10. (a) 0.48 V 12. 0.28 V 15. 1.56 V Section 14.3 Practice (p. 644) 5. (a) 0.80 V (b) 1.23 V 6. (a) 1.48 V (b) 0.00 V Practice (p. 645) 12. (a) 0.43 V (b) 0.29 V 13. 1.30 V Page 788 Unit 7 Review (pp. 667–669) 41. 5.78 g 42. 8.56 mmol/L 45. (a) 1.22 V (b) 0.80 (c) 0.00 V 46. (a) 1.90 V (b) 1.23 V (c) 1.64 V 47. (b) 1.23 V 48. (b) 2.19 V 49. (a) 1.99 V (b) 590 s (or 9.84 min) 50. 2.98 kA 51. 20.1 min 52. 1.0 kmol/h 54. (b) 1.20 V Section 14.4 Practice (p. 653) 1. 45 C 2. 3.89 A 3. 7.13 C 4. 3.91 min Practice (p. 654) 5. 41 mmol 6. 3.16 h 7. 1.2 A Section 14.4 Questions (p. 657) 1. 2.80 mmol 2. 0.58 t 3. 82.8 min 4. 52.8 kA 5. (a) 1.63 t (b) 4.76 t 6. 0.174 mol/L 7. 24.42 g 8. 0.102 g 9. (a) 26 g (b) 25.4 min 10. 21. 3 g 11. 25.0 A 12. 0.766 g; 0.71 g; 7% 14. (c) 483 g (d) 41.9 g Chapter 14 Review (p. 665) 18. (d) 0.93 V 21. (d) 0.00 V 23. 50.3 kg 24. 0.125 A 788 Appendix A Unit 8 Are You Ready? (pp. 672–673) 5. (a) 5.94 mol/L (b) 0.220 mol/L (c) 0.0403 mol/L (d) 0.0446 mol/L Chapter 15 Section 15.1 Practice (p. 682) 4. (a) 2.00 mol (b) 70.0% 6. (c) 1.00 L (d) 60% Lab Exercise 15.B (p. 686) 0.46 Section 15.1 Questions (pp. 688–689) 3. (b) 14 mol 5. 51 6. 0.11 mol/L 7. (c) 0.200 mol (d) 0.80 mol (e) 0.40 mol (f) [HBr(g)] = 0.100 mol/L; [H2(g)] = 0.20 mol/L; [Br2(g)] = 0.20 mol/L (g) 4.0 8. 54.1 9. 1.5 10. (a) 0.78 mol/L (b) 0.39 mol Chapter 15 Review (p. 705–706) 19. 0.0013 mol/ L 20. 0.0403 mol/ L 21. 0.032 26. (a) 0.068 27. (a) 5.07 mol/L (b) 7.60 mol/L 28. 1.00 mol/L 32. (b) 0.0029 mol/L Chapter 16 Section 16.1 Practice (p. 716) 1. 2.3 1012 mol/L 2. 3.3 1011 mol/L 3. 2.5 1013 mol/L 4. 7.2 1013 mol/L 5. 1.4 1014 mol/L 6. 1.8 107 % Practice (p. 718) 7. (a) 1.8 1012; 2.26; 11.74 4 109; 3 106; 8.4 5.0 104; 3.30; 10.70 4.0 104; 2.5 1011; 3.40 8. 14.64; 0.64 9. 0.09 g Section 16.1 Questions (p. 721) 4. (b) 7.8 106 mol/L; 5.11 5. 7.7 1012 mol/L 6. 7.40 7. 3 106 mol/L 8. 1000 (103) 9. 0.372 10. 0.25 g 11. 4.27 12. 0.016; 14.02 13. 2.42; 11.58 14. 18 mg Section 16.3 Practice (p. 743) 2. (a) 0.20 mol/L (c) 1.9 103 mol/L (d) 2.64 (f) 4.84 5. (a) 1.16% (b) 1.36 105 6. (a) 3.7% (b) 1.35 105; 1.4 104 NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 789 Appendix A 7. (b) 3.5 102 mol/L; 3.5 102 mol/L; 1.45; 1.8% 8. (a) 0.26 mol/L; 0.58; 2.6% 9. (a) 8.2 105 Practice (p. 746) 12. 7.7 1010 13. 4.2 1010 Section 16.3 Questions (p. 750) 1. 10.27 2. 11.23 4. 4.77 5. 1.4 103 6. 1.3 1010 7. 4.2 104 mol/L 10. (a) 9.95 (b) 4.25 (c) 3.85 Section 16.4 Practice (pp. 762–763) 13. (a) < 7 NEL (b) > 7 (c) ~ 7 (d) < 7 Chapter 16 Review (p. 773) 17. (a) 0.10 mol/L; 1.00 (b) 4.2 103 mol/L; 2.38 (c) 9.4 105 mol/L; 4.03 18. (a) 5.8 107 20. 7; 7 21. 10.0 to 11.4; 2.5 103 to 2.5 103 mol/L 22. 0.019%; 8.46; 5.54; 2.9 106 mol/L Unit 8 Review (pp. 775779) 26. 0.62 mol/L; 0.62 mol/L; 1.38 mol/L; 0.62 mol/L 29. 5.0 to 5.2; 1 105 mol/L to 6 106 mol/L 35. (c) 25 mL; 50 mL 36. 3.5 mol/L; 3.5 mol/L 37. 2.3 38. 0.882 mol/L 39. (a) (i) 7.00; 10 mL 45. 46. 47. 48. 49. 50. 51. (ii) 13.00 (iii) 12.60 (v) 11.8 (vi) 1.9 1.24%; 1.6 105 6.5 103 %; 4.2 1010 1.5 104 mol/L; 0.58; 0.30% (b) 3.1 102 mol/L; 1.51; 1.5% (c) 2.1 1011 mol/L 0.012%; 8.14; 5.86; 1.4 106 mol/L 7.9 1010 (a) 1.5 103; 5.0 102; 1.9 101 Numerical Answers to Questions 789 A Appendix A-F_Chem20 11/1/06 10:36 AM Appendix B Page 790 SCIENTIFIC PROBLEM SOLVING B.1 Scientific Problem-Solving Model Scientists ask questions and seek concepts to answer these questions by applying consistent, logical reasoning to describe, explain, and predict observations, and by doing experiments to test hypotheses or predictions from these hypotheses. In this way science progresses using a general model for solving problems and employing specific processes as part of a problemsolving strategy. Every investigation in science has a purpose; for example: • to create a scientific concept (a theory, law, generalization, or definition) • to test a scientific concept • to use a scientific concept, e.g., in chemical analysis Once you know the purpose, you need a problem and a general design. For example, if the purpose is to perform a chemical analysis to determine the quantity of a substance, then possible designs include distillation and precipitation. Once you choose a design, there are many specific questions that you might ask, many possible reactants you might choose, and many other variables you might need to consider. B.2 Investigation Report Outline An investigation report is the final result of your problem solving. Your report should follow the model outlined in Figure 1. As a further guide, use the information and instructions for the specific processes listed below. The parts of the investigation report that you are to provide are indicated in the text in a checklist (Figure 2). Report Checklist Purpose Problem Hypothesis Prediction Design Materials Procedure Evidence Analysis Evaluation (1, 2 and/or 3) Figure 2 Shaded circles indicate the parts you are expected to complete in a particular investigation report. One or more parts of an Evaluation may be required, as indicated by the numbers. Purpose Problem Purpose Hypothesis and/or Prediction Design Materials Problem Prediction Procedure Evidence Analysis Appendix B The Problem is a specific question to be answered in the investigation. If appropriate, you should state the question in terms of manipulated and responding variables. In most cases, the problem is chosen for you. Only when creating a concept will the Purpose and the Problem be the same. Hypothesis Evaluation The hypothesis is an (often untested) empirical or theoretical concept that provides a possible explanation for a natural or technological phenomenon. Only some kinds of investigations require a hypothesis, such as investigations that test a hypothesis using a general question as the Problem. Synthesis Prediction Figure 1 A scientific problem-solving model helps to guide your laboratory work, but does not illustrate the complexity of the work. 790 Although this is usually provided, you will be expected to identify the purpose of an investigation before, during, and after your laboratory work. Most often, the purpose is to create, test, or use a chemistry concept. The Prediction is the expected answer to the Problem according to a scientific concept (for example, a hypothesis, theory, law, or generalization) or another authority (for NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 791 Appendix B example, a reference source or a label on a bottle). Write your Prediction using the format, “According to [an authority], [answer to the Problem].” Include your qualitative and quantitative reasoning (based upon the authority) with the Prediction. Design The Design provides a brief overview of the Procedure to obtain an answer to the Problem. Included in the Design are reacting chemicals and, if applicable, brief descriptions of diagnostic tests, variables, and controls. Write your Design as a paragraph of one to three sentences. Materials This section consists of a complete list of all equipment and chemicals, in columns, including sizes and quantities. Appendix C.3, page 797, shows laboratory equipment, including common sizes. Procedure The Procedure is a detailed set of instructions designed to obtain the evidence needed to answer the Problem. Write a list of numbered steps in the correct sequence, including any safety and waste disposal instructions (Appendix E, page 807). Whenever possible, repeat measurements several times. (Design, Materials, Procedure, and Skills). Evaluation of Lab Exercises (simulated investigations) will not usually involve Part 1. Only if you are confident that no major flaws are present can you proceed to the second part. In Part 2, you use the results of the experiment to evaluate the Prediction (if one was made) and the Hypothesis (if there is one). This assumes that a prediction is being tested in an experiment. If it is the experimental design that is being tested, then the two parts of the evaluation would be reversed and the percent difference is used to judge the success of the design. The last part of the Evaluation, Part 3, comes back, full circle, to the Purpose of the investigation. Was the Purpose fulfilled? The parts of the Evaluation you will be expected to complete are shown in parentheses after Evaluation in the Report Checklist. Write your Evaluation in paragraph form, using the topic sentences suggested below or an adaptation of them. Some of the more important criteria for a judgment are listed as questions; use selected questions to guide your judgments. Show as much independent, critical, and creative thought as possible in support of your judgments. Part 1. Evaluation of the Investigation • Evidence The Evidence includes all qualitative and quantitative observations relevant to answering the Problem. Organize your evidence in tables whenever possible (Appendix F.4, page 815). Be as precise as possible in your measurements and include any unexpected observations that may affect your answer and its certainty (in significant digits). Scientific honesty demands that you report all evidence collected and not just the evidence you think is correct or “normal.” Were you able to answer the Problem using the chosen experimental design? Are there any obvious flaws in the design? What alternative designs (better or worse) are available? As far as you know, is this design the best available in terms of controls, variables, efficiency, and safety? • Evaluation Part 1 of the Evaluation of an investigation that you actually perform usually involves judging the validity of the experiment NEL “The materials are judged to be adequate/ inadequate because ...” Did you have all of the necessary materials? Was the equipment of reasonable quality? What materials could be improved to obtain better results? Analysis The Analysis includes manipulations, interpretations, and calculations based on the evidence. Tables and graphs that include or facilitate interpretations and calculations are included in the Analysis. You may need to differentiate between relevant and irrelevant observations. Communicate your work clearly and logically. Conclude the Analysis with a statement of your experimental answer to the Problem, including a phrase such as, “According to the evidence gathered in this experiment, [answer to the Problem statement].” “The design of the investigation [name or describe in a few words] is judged to be adequate/ inadequate because …” • “The procedure is judged to be adequate/ inadequate because …” Were the steps that you used in the laboratory correctly sequenced, and adequate to gather sufficient evidence? What improvements could be made to the procedure, such as more trials? • “The technological skills are judged to be adequate/inadequate because …” Which specialized skills, if any, might have the greatest effect on the evidence gathered? Was the evidence from repeated trials reasonably similar? Scientific Problem Solving 791 B Appendix A-F_Chem20 11/1/06 10:36 AM Page 792 How can the evidence gathered be improved? • “Based upon my evaluation of the experiment, I am not/moderately/very certain of my experimental evidence. The sources of uncertainty or error are …” State the sources and your confidence in the experimental evidence. What would be an acceptable total of the experimental error (1%, 5%, or 10%)? Part 2. Evaluation of the Prediction and Authority Being Tested • If applicable, “the percent difference between the experimental result and the predicted value is…” % difference experimental value predicted value 100 predicted value How does this difference compare with your estimated total uncertainty or experimental error? • “The prediction is judged to be verified/ inconclusive/falsified because …” Does the predicted answer clearly agree with the experimental answer reported in your analysis? Can the percent difference be accounted for by the sources of error (percent error) listed above? • “The authority being tested [name the authority or hypothesis (reasoning)] is judged to be acceptable/ unacceptable in this experiment because …” Was the prediction verified, inconclusive, or falsified? How confident do you feel about your judgment? Part 3. Revisiting the Purpose Did you accomplish the Purpose of this investigation? Is there a need for additional investigations to better achieve the Purpose? Notes on Data and Evidence Data Data may be found on data sheets, in data tables, and in databases. Data from one of these sources can become evidence with the purpose to create, test, or use a scientific concept. Evidence is data with a scientific purpose. Common Sources of Experimental Error • conditions (e.g., SATP) not controlled • impure reactants or products • any measurement process • incomplete reaction • judgment of colour (e.g., indicator) • loss of solid in a filtration (stuck to glass or passed through filter) Experimental Error and Percent Difference Some people and books use the term “percent error” in place of “percent difference.” In this textbook, we use two percentages: One is an estimate of the total expected experimental error (Evaluation, Part 1), and the other is the actual difference (the percent difference) you determined based on your prediction and analysis (Evaluation, Part 2). The crucial point is how these two percentages compare. No experiment can ever be expected to be perfect. For example, if the equipment you used is only precise to / 5%, then any percent difference you obtain that is less than or equal to 5% is as good a result as can be expected. If the percent difference is larger than the reasonably acceptable experimental error, then the prediction is falsified. If the percent difference is equal to or less than the experimental error, then the prediction is verified. • incomplete drying of a product • manipulative skill Do not use “human error” as a source of uncertainly or experimental error. Percent Yield versus Percent Difference Replication An authority may be judged unacceptable in one experiment. This does not mean the authority is immediately discarded. Replication by independent workers is always required to refute any accepted theory. In most experiments, a percent difference is a measure of accuracy. In some experiments in which a product is collected and measured, a percent yield is used instead of a percent difference. actual quantity obtained % yield predicted (maximum) quantity 100 792 Appendix B NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 793 Appendix B B.3 Sample Investigation Report The Reaction of Hydrochloric Acid with Zinc Purpose The purpose of this investigation is to test one of the ideas of the collision–reaction theory. Report Checklist Purpose Problem Hypothesis Prediction Design Materials Procedure Evidence Analysis Evaluation (1, 2, 3) Problem 2. Carefully place a piece of Zn(s) into the hydrochloric How does changing the concentration of hydrochloric acid affect the time required for the reaction of hydrochloric acid with zinc? 3. Measure and record the time required for all of the Prediction According to the collision–reaction theory, if the concentration of hydrochloric acid is increased, then the time required for the reaction with zinc will decrease. The reasoning that supports the prediction is that a higher concentration produces more collisions per second between the hydrochloric acid entities and the zinc atoms. More collisions per second would produce more reactions per second and, therefore, a shorter time required to consume the zinc. Design Different known concentrations of excess hydrochloric acid react with the same quantity of zinc metal. The time for the zinc to completely react is measured for each concentration of acid solution. The concentration of hydrochloric acid is the manipulated variable and time is the responding variable. The temperature, mass, and surface area of zinc, and volume of acid are the controlled variables. acid solution and note the starting time of the reaction. zinc to react. 4. Repeat steps 1 to 3 using 1.5 mol/L, 1.0 mol/L, and 0.5 mol/L HCl(aq). 5. Neutralize the acid with a weak base and then pour it down the sink with the water running. Evidence Gas bubbles formed immediately on the surface of the zinc strip when it was placed into the hydrochloric acid solution. The bubbles appeared to form more rapidly when the concentration of the acid was higher. The Reaction of HCl(aq) with Zn(s) Concentration of HCl(aq) (mol/L) Materials Procedure 1. Transfer 10 mL of 2.0 mol/L HCl(aq) into an 18 150 mm test tube. Avoid contact with skin, eyes, clothing, or the desk. If you spill this acid on your skin, wash immediately with lots of cool water. NEL 2.0 70 1.5 80 1.0 144 0.5 258 Analysis The Reaction of HCl(aq) with Zn(s) 300 Time (s) lab apron eye protection (4) 10 mL graduated cylinders (4) 18 150 mm test tubes and test-tube rack clock or watch (precise to the nearest second) four pieces of a zinc metal strip (5 mm 5 mm) HCl(aq): 2.0 mol/L, 1.5 mol/L, 1.0 mol/L, 0.5 mol/L a weak base (e.g., baking soda) Time for reaction (s) 200 100 0 0.5 1.0 1.5 2.0 Concentration of HCl(aq) (mol/L) Scientific Problem Solving 793 B Appendix A-F_Chem20 11/1/06 10:36 AM Page 794 According to the evidence obtained, increasing the concentration of hydrochloric acid decreases the time required for the complete reaction of a fixed quantity of zinc. Evaluation The design, reacting zinc with excess hydrochloric acid, is judged to be adequate because this experiment produced the type of evidence needed to answer the problem with a high degree of certainty. There are no obvious flaws in this design. In my judgment, the design is efficient and safe, and all necessary variables are controlled. The materials appear to be adequate because the quality of the evidence was sufficient to give a clear answer to the problem. Using a pipette would provide better precision than a graduated cylinder but this would not change the overall result. The procedure is also judged adequate because it produced sufficient evidence. Possible improvements include extending the range of concentrations and performing more trials for each concentration. The reaction could be done in a container that allowed better mixing. The technological skills are judged adequate because no specialized skills were involved. Timing the start of the reac- tion may have some uncertainty but the lack of multiple trials makes this difficult to judge. Based upon my evaluation of the experiment, I am very certain about the experimental results. Sources of uncertainty in this investigation include: measurement errors for volume and time, the purity and surface area of the zinc metal strip, the concentration of the acid, and a little uncertainty in estimating when the last bit of zinc had reacted. An estimate of the total effect of all experimental uncertainties is about 5%. The prediction is judged to be verified because the qualitative observations and the graph clearly indicate that the reaction time decreases as the concentration increases. There is little deviation from a smooth curve in the graphed results. The collision–reaction theory is judged to be acceptable in this experiment because the prediction was clearly verified. I am quite confident in this judgment because other groups in the class obtained similar results. The purpose of this investigation—to test one idea of the collision–reaction theory—was accomplished but only for one reaction. Replication with many other reactions would need to be investigated to have a more valid test. B.4 The Nature of Scientific Research Citizens in a democratic society are often required to read and interpret media reports of scientific research. Health and environment research reports are, for example, commonly portrayed in the media. Sometimes the research reports appear to contradict each other and sometimes the reports promote more uncertainty than certainty. Understanding the terminology and concepts for describing a research study is increasingly important for responsible citizenry. Listed below are some of the terms and concepts that will help you both answer questions in this textbook and understand and critique media reports of research. Types of Studies correlational study—the connection or degree of agreement (e.g., –0.3, 1.0) is sought between two variables, often without controlling for other variables; correlational studies often lead to cause-and-effect studies cause-and-effect study—one variable is manipulated and all other variables, other than the responding variable, are controlled control experiment—see cause-and-effect study clinical trial—a controlled study involving people; usually a final-stage, double-blind study 794 Appendix B Design Factors term of study—the duration of the experiment e.g., observations over 5 s, 30 min, 3 mon or 15 a; long-term studies are most often preferred sample size—the number of entities or people in a study; generally large sample sizes are preferred random sample—one chosen randomly from the population of entities (to reduce bias) replication—repetition of a study, generally, by an independent research group placebo—in medicinal experiments, an inactive item (e.g., sugar pill) or treatment given to the control group placebo effect—a beneficial effect arising from a patient’s expectations; present in both the control group and the experimental group single blind—the subject (e.g., patient) does not know whether she/he has received the treatment or a placebo, but the experimenter knows double blind—neither the subject (e.g., patient) nor the directly involved experimenter knows whether the subject has received the treatment or a placebo control—a standard or comparison value, or procedure (e.g., leaving one of several identical samples unaltered for comparison), or a placebo NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 795 Appendix B control group—a comparison group that does not receive the experimental treatment experimental group—a group that receives the experimental treatment ways of knowing—methods used to obtain knowledge or information; examples include traditional (Aboriginal), empirical, theoretical, referenced, and memorized Scientific Attitudes Nature of Evidence and Results anecdotal—based upon personal experience or hearsay reliable—reproducible or consistent time after time valid—judged to be supported by adequate designs, materials, procedures, and skills accurate—judged to be true or agreeing with the accepted value precise—closely related or very similar; related to reproducibility of results statistical bias—a sampling or testing error caused by systematically favouring some outcomes over others random result—a result that could be expected on the basis of probability (e.g., 50% heads and tails when flipping a large number of coins) coincidence—a result that is accidental and irrelevant to the study significant difference—a difference that is greater than could be randomly expected when an experimental group and a control group are compared certainty—the degree to which something is accepted by an individual or community (e.g., the evidence may have a high or low degree of certainty); measured by, for example, counting significant digits scientific attitude—a disposition or demonstration of feelings or thoughts (e.g., honesty, objectivity, willingness to change, respect for evidence, critical mindedness, suspended judgment, open-mindedness, and questioning predisposition) tolerance of uncertainty—the degree to which people and institutions tolerate uncertainty (without claiming absolute certainty), although they strive for greater and greater certainty COMMUNICATION example 1 Create an experimental design to test a new drug to promote weight loss. Solution Randomly selected control and experimental groups of 1000 volunteers are studied over two years. Both receive pills: The experimental group receives the drug; the control group unknowingly receives a placebo. Technicians, who do not know which group each person is in, record the weight of the subjects every month. Experimenters, who never meet or see the volunteers, analyze the evidence gathered. Reporting Research refereed journal—an academic journal for which research papers are sent to subject experts to determine whether the report is of sufficient quality to publish; also called peer-reviewed journal abstract—a short summary describing the research processes and results Science–Technology–Society (STS) Issues risk–benefit analysis—a process of gathering and analyzing evidence that leads to decision making (and to an evaluation of the process itself) stewardship—actively supervising and managing an entity or event (e.g, the environment) perspective—a point of view or way of analyzing an object or event multiperspective—based upon positive and negative evidence and arguments from many perspectives (e.g., scientific, technological, economic, environmental, political, legal, ethical, social, and emotional) NEL COMMUNICATION example 2 Act as a referee (peer-reviewer) to critique the following experimental design including, if necessary, suggestions for improvement. Ten volunteers are provided with their horoscope for the test day. The volunteers orally respond in a group to the question: Does this horoscope describe your personality and life situation? Solution This experimental design is very inadequate because: • ten volunteers is a very small sample size; the number needs to be at least 100 or more, randomly selected from thousands • to control the horoscope variable, all subjects should be provided with the same horoscope • to control subject interaction and influence, subjects should be isolated from one another • to provide for accurate reporting of the subjects’ responses, investigators should make audio or audiovisual recordings Scientific Problem Solving 795 B Appendix A-F_Chem20 11/1/06 Appendix C 10:36 AM Page 796 TECHNOLOGICAL PROBLEM SOLVING The goal of technological problem solving is to solve practical problems by developing or revising a product or a process. The product or the process must fulfill its function, but it is not essential to understand why or how it works. Products are evaluated based on criteria such as simplicity, reliability, and cost. Technological processes are also evaluated by their efficiency. Technological products and processes may have both intended and unintended consequences. Therefore, it is important that various perspectives, such as ecological, economic, and political, are used in any assessment. For example, chlorofluorocarbons may be simple and inexpensive to make, and they may be useful for a particular function, but their effect on the ozone layer in the upper atmosphere must also be considered. Processes such as the chlorine bleaching of wood pulp may be efficient, but they may adversely affect an ecosystem. We often look to technological fixes as solutions for problems. Ecological, economic, political, legal, ethical, and/or social efforts by individuals or groups can often lead to more sustaining solutions than quick technological fixes. Chemistry has always been closely associated with technology. Part of technology is the laboratory equipment, processes, and procedures used in both chemical and technological research and development. In modern chemistry, simple equipment and processes, such as beakers and filtration, are still used but chemistry also depends on sophisticated technology, such as computers, to store and manipulate the evidence collected. C.1 Technological Problem-Solving Model Technological problem solving is similar in some ways to scientific problem solving but its purpose differs. A characteristic of technological problem solving is a systematic, trial-and-error manipulation of variables (Figure 3). Variables are predicted and tested and the results are evaluated. When the cycle is repeated many times, the most effective set of conditions can be determined. Compare this model with the scientific problem-solving model in Figure 1, on page 790. Technological problem-solving contexts include industrial, commercial, and consumer. The general process for technological problem solving is similar in all of these contexts. Technological problem solving is very common to us in our everyday lives. Learning more about this systematic trial-anderror approach can help us on an everyday basis. Technological Problem Prediction of Variables Evaluation Product/Process Design Product/Process Analysis Evidence Synthesis Figure 3 A technological problem-solving model C.2 Investigation Reports Investigation reports for technological problem-solving investigations can use the same headings as those for scientific problem-solving investigations (Appendix B.2, page 790). Some key differences between these two types of reports are Purpose The purpose will be to solve a specific, practical problem by developing or revising a product or process. 796 Appendix C Evaluation Evaluation criteria can be many and varied. In some cases, it will be sufficient to demonstrate that the product or process works for the materials used. You may also be asked to judge the simplicity, reliability, and efficiency of the product or process, recognize its value and limitations, and evaluate it from a variety of perspectives (Appendix D.2, page 806). NEL Appendix A-F_Chem20 11/1/06 10:36 AM Page 797 Appendix C C.3 Laboratory Equipment 10 mL 25 mL 50 mL 100 mL 500 mL 1000 mL 13 × 100 mm 18 × 150 mm 25 × 200 mm meniscus finder pipette bulb mortar and pestle U-tube test tube 1 mL 10 mL 25 mL 1 mL 10 mL C 100 mL 250 mL 500 mL 1000 mL 2000 mL beaker 50 mL 100 mL 150 mL 250 mL 400 mL 600 mL 1000 mL graduated cylinder dropper volumetric pipette graduated pipette 125 mL 250 mL 500 mL 1000 mL volumetric flask Erlenmeyer flask 50 mL burette dropper bottles watch glass burette (utility) clamp funnel thermometer wash bottle evaporating dish clamp holder extension clamp test-tube clamp funnel rack well plate (microplate) crucible tongs wire gauze laboratory scoop beaker tongs Figure 4 Common lab equipment NEL weighing boat Glassware is breakable and should always be handled with care. Technological Problem Solving 797 Appendix A-F_Chem20 11/1/06 10:37 AM Page 798 Using a Laboratory Burner The procedure outlined below should be practised and memorized. Note the safety caution. You are responsible for your safety and the safety of others near you. 1. Turn the air and gas adjustments to the off position (Figure 5). 2. Connect the burner hose to the gas outlet on the bench. 3. Turn the bench gas valve to the fully on position. 4. If you suspect that there may be any gas leaks, replace the burner. (Give the leaky burner to your teacher.) 5. While holding a lit match above and to one side of the barrel, open the burner gas valve until a small yellow flame results (Figure 6). If a striker is used instead of matches, generate sparks over the top of the barrel (Figure 7). 6. Adjust the air flow and obtain a pale blue flame with a dual cone (Figure 8). In most common types of laboratory burners, rotating the barrel adjusts the air intake. Rotate the barrel slowly. If too much air is added, the flame may go out. If this happens, immediately turn the gas flow off and relight the burner following the procedure outlined above. If your burners have a different kind of air adjustment, revise the procedure accordingly. 7. Adjust the gas valve on the burner to increase or decrease the height of the blue flame. The hottest part of the flame is the tip of the inner blue cone. Usually a 5 to 10 cm flame, which just about touches the object heated, is used. barrel air valve gas supply gas valve 8. Laboratory burners, when lit, should not be left un- attended. If the burner is on but not being used, adjust the air and gas intakes to obtain a small yellow flame. This flame is more visible and, therefore, less likely to cause problems. When lighting or using a laboratory burner, never position your head or fingers directly above the barrel. Tie back long hair and sleeves. Figure 5 The parts of a common laboratory burner Figure 6 A yellow flame is a relatively cool flame and is easier to obtain than a blue flame when lighting a burner. A yellow flame is not used for heating objects because it contains a lot of black soot. 798 Appendix C Figure 7 To generate a spark with a striker, pull up and across on the side of the handle containing the flint. Figure 8 A pale, almost invisible flame is much hotter than a yellow flame. The hottest point is at the tip of the inner blue cone. NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 799 Appendix C Using a Laboratory Balance There are two types of balances: electronic (Figure 9) and mechanical (Figure 10). All balances must be handled carefully and kept clean. Always place chemicals into a container such as a beaker or plastic boat to avoid contamination and corrosion of the balance pan. To avoid error due to convection cur- Figure 9 An electronic balance rents in the air, allow hot or cold samples to return to room temperature before placing them on the balance. Always record masses showing the correct precision. On a centigram balance, mass is measured to the nearest hundredth of a gram (0.01 g). When it is necessary to move a balance, hold the instrument by the base and steady the beam. Never lift a balance by the beams or pans. To avoid contaminating a whole bottle of reagent, do not scoop diectly from the original container of a chemical. Pour a quantity of the chemical into a clean, dry beaker or bottle, from which samples can be taken. Another acceptable technique for dispensing a small quantity of chemical is to rotate or tap the chemical bottle. displayed. Air currents or the high sensitivity of the balance may cause the last digit to vary. 4. Remove the container and sample. There is a video demonstration of this technique on the Nelson Web site. www.science.nelson.com GO C Using a Mechanical Balance Different kinds of mechanical balances are shown in Figures 10(a) and (b). Some general procedures apply to most of them. 1. Clean and zero the balance. (Turn the zero adjustment screw so that the beam is balanced when the instrument reads 0 g and no load is on the pan.) 2. Place the container on the pan. 3. Move the largest beam mass one notch at a time until the beam drops, and then move the mass back one notch. 4. Repeat this process with the next smaller mass and continue until all masses have been moved and the beam is balanced. If you are using a dial type balance, the final step will be to turn the dial until the beam balances, as shown in Figure 10(c). 5. Record the mass of the container. Using an Electronic Balance Electronic balances are sensitive to small movements and changes in level; do not lean on the counter when using the balance. 1. Place a container or weighing paper on the balance. 2. Reset (tare) the balance so the mass of the container registers as zero. (a) 3. Add chemical until the desired mass of chemical is (b) 6. Set the masses on the beams to correspond to the total mass of the container plus the desired sample. 7. Add the chemical until the beam is once again balanced. 8. Remove the sample from the pan and return balance to the zero position. (c) Figure 10 (a) On this type of mechanical balance, the sample is balanced by moving masses on several beams. (b) Another type of mechanical balance has beams for the larger masses and a dial for the final adjustment. (c) The dial reading on this balance with a vernier scale is 2.34 g. To read the hundredth of a gram, look below the zero on the vernier, and then look for the line on the vernier that lines up best with a line on the dial. NEL Technological Problem Solving 799 Appendix A-F_Chem20 11/1/06 10:37 AM Page 800 Using a Multimeter 5. Rinse the probes with pure water before testing A multimeter (Figure 11) is a device that measures a variety of electrical quantities, such as resistance, voltage, and current. 6. Shut off the meter by using either the on/off switch or (a) (b) another sample. by turning the dial to any setting other than “Resistance.” Voltage Measurements of Cells and Batteries 1. Set the dial to the appropriate value on the direct current volts (DCV) scale; for example, 3 V. 2. The black lead (labelled negative or COM) is normally connected to the anode, and the red lead (positive) is connected to the cathode of a voltaic cell. 3. Make a firm contact between each metal probe and an electrode of the cell. (Press firmly with the pointed probe or use leads with an alligator clip.) Figure 11 (a) An analog meter has a needle that moves in front of a labelled scale. (b) A digital meter gives a direct reading with appropriate units. 4. On analog meters (those with a needle), read the scale Conductivity Measurements of Solutions or a digital meter registers a negative number, then switch the connections to the cell. 1. Set the dial on the meter to one of the higher values on the ohm (Ω) scale; for example, R 100 or R 1 K. 2. Touch the two metal probes together to check the battery. If the needle does not deflect significantly (more than one-half scale), have your teacher adjust the meter or replace the battery. 3. Test a sample of pure water as a control and note the movement of the needle. 4. Test your aqueous sample and record the deflection of the needle according to your teacher’s instructions. corresponding to the meter value you set in step 1. 5. If the needle attempts to move to the left off the scale Using a Pipette A pipette is a specially designed glass tube used to measure precise volumes of liquids. There are two types of pipettes and a variety of sizes for each type. A volumetric pipette (Figure 12) transfers a fixed volume, such as 10.00 mL or 25.00 mL, accurate to within 0.04 mL. A graduated pipette (Figure 13) measures a range of volumes, just as a graduated cylinder does. A 10 mL graduated pipette delivers volumes accurate to within 0.1 mL. There is a video demonstration of this technique on the Nelson Web site. www.science.nelson.com GO Figure 12 A volumetric pipette delivers the volume printed on the label if the temperature is near room temperature. Figure 13 To use a graduated pipette, you must be able to start and stop the flow of the liquid. 800 Appendix C NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 801 Appendix C 1. Rinse the pipette with small volumes of distilled water using a wash bottle, and then with the sample solution. A clean pipette has no visible residue or liquid drops clinging to the inside wall. Rinsing with aqueous ammonia and scrubbing with a pipe cleaner might be necessary to clean the pipette. 2. Hold the pipette with your thumb and fingers near the top. Leave your index finger free. 3. Place the pipette in the sample solution, resting the tip on the bottom of the container if possible. Be careful that the tip does not hit the sides of the container. 4. Squeeze the bulb into the palm of your hand and place the bulb firmly and squarely on the end of the pipette (Figure 14) with your thumb across the top of the bulb. 5. Release your grip on the bulb until the liquid has risen above the calibration line. This may require bringing the level up in stages: remove the bulb, put your finger on the pipette, squeeze the air out of the bulb, re-place the bulb, and continue the procedure. 7. Wipe all solution from the outside of the pipette using a paper towel. 8. While touching the tip of the pipette to the inside of a waste beaker, gently roll your index finger (or squeeze the valve of the dispensing bulb) to allow the liquid level to drop until the bottom of the meniscus reaches the calibration line (Figure 16). To avoid parallax errors, set the meniscus at eye level. Stop the flow when the bottom of the meniscus is on the calibration line. Use the bulb to raise the level of the liquid again if necessary. 9. While holding the pipette vertically, touch the pipette tip to the inside wall of a clean receiving container. Remove your finger or adjust the valve and allow the liquid to drain freely until the solution stops flowing. 10. Finish by touching the pipette tip to the inside of the container held at about a 45° angle (Figure 17). Do not shake the pipette. The delivery pipette is calibrated to leave a small volume in the tip. Never use your mouth to draw a liquid up a pipette. Always use a pipette bulb. 6. Remove the bulb, placing your index finger over the top. If you are using a dispensing bulb (Figure 15), it remains attached to the pipette. Figure 14 Release the bulb slowly. Pressing down with your thumb placed across the top of the bulb maintains a good seal. Setting the pipette tip on the bottom slows the rise or fall of the liquid. NEL Figure 15 A dispensing pipette bulb uses a small valve in the side stem to control the flow of liquid in a pipette. Figure 16 To allow the liquid to drop slowly to the calibration line, it is necessary for your finger and the pipette top to be dry. Also keep the tip on the bottom to slow down the flow. Figure 17 A vertical volumetric pipette is drained by gravity and then the tip is placed against the inside wall of the container. A small volume is expected to remain in the tip. Technological Problem Solving 801 C Appendix A-F_Chem20 11/1/06 10:37 AM Page 802 C.4 Laboratory Processes The processes or experimental procedures listed below are part of common designs used in scientific or technological laboratories. Crystallization Crystallization is used to separate a solid from a solution by evaporating the solvent or lowering the temperature. Evaporating the solvent is useful for quantitative analysis of a binary solution; lowering the temperature is commonly used to purify and separate a solid whose solubility is temperature-sensitive. Chemicals that have a low boiling point or decompose on heating cannot be separated by crystallization using a heat source. Filtration In filtration, solid is separated from a mixture using a porous filter paper. The more porous papers are called qualitative filter papers. Quantitative filter papers allow only invisibly small particles through the pores of the paper. There is a video demonstration of this technique on the Nelson Web site. www.science.nelson.com GO 1. Set up a filtration apparatus (Figure 19): stand, funnel holder, filter funnel, waste beaker, wash bottle, and a stirring rod with a flat end for scraping. Figure 19 The tip of the funnel should touch the inside wall of the collecting beaker. 1. Measure the mass of a clean beaker or evaporating dish. 2. Place an accurate volume of the solution in the container. 3. Set the container aside to evaporate the solution slowly, or warm the container gently on a hot plate or with a laboratory burner. 4. When the contents appear dry, measure the mass of the container and solid (Figure 18). 2. Fold the filter paper along its diameter, and then fold it again to form a cone. A better seal of the filter paper on the funnel is obtained if a small piece of the outside corner of the filter paper is torn off (Figure 20). Figure 18 When the substance has crystallized, it may appear dry but small quantities of water may still be present. To be certain the solid is dry, it must be heated until the mass becomes constant. (a) (b) (c) (d) Figure 20 To prepare a filter paper, fold it in half twice, and then remove the outside corner as shown. 3. Measure and record the mass of the filter paper after 5. Heat the solid with a hot plate or burner, cool it, and measure the mass again. 6. Repeat step 5 until the final mass remains constant. (Constant mass indicates that all of the solvent has evaporated.) 802 Appendix C removing the corner. 4. While holding the open filter paper in the funnel, wet the entire paper and seal the top edge firmly against the funnel. NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 803 Appendix C 5. With the stirring rod touching the spout of the Figure 22 Raise the meniscus finder along the back of the neck of the volumetric flask until the meniscus is outlined as a sharp, black line against a white background. beaker, decant most of the solution into the funnel (Figure 21). Transferring the solid too soon clogs the pores of the filter paper. Keep the level of liquid about two-thirds up the height of the filter paper. The stirring rod should be rinsed each time it is removed. Figure 21 Pouring along the stirring rod prevents drops of liquid from going down the outside of the beaker when you stop pouring. 1. (Prelab) Calculate the required mass of solute from the volume and concentration of the solution. 2. Measure the required mass of solute in a clean, dry beaker or weighing boat. (Refer to “Using a Laboratory Balance” on page 799.) 3. Pour less than one-half of the final volume of pure 6. When most of the solution has been filtered, pour the remaining solid and solution into the funnel. Use the wash bottle and the flat end of the stirring rod to clean any remaining solid from the beaker. 7. Rinse the stirring rod and the beaker. 8. Wash the solid two or three times to ensure that no solution is left in the filter paper. Direct a gentle stream of water around the top of the filter paper. 9. When the filtrate has stopped dripping from the funnel, remove the filter paper. Press your thumb against the thick (three-fold) side of the filter paper and slide the paper up the inside of the funnel. water into a beaker. Transfer the solute to the water. Stir to dissolve. 4. Transfer the solution and all water used to rinse the equipment into a clean volumetric flask. (The beaker and any other equipment should be rinsed two or three times with pure water.) 5. Add pure water, using a medicine dropper for the final few millilitres while using a meniscus finder to set the bottom of the meniscus on the calibration line. 6. Stopper the flask and mix the solution by slowly inverting the flask several times. 10. Transfer the filter paper from the funnel onto a labelled watch glass and unfold the paper to let the precipitate dry. 11. Determine the mass of the filter paper and dry precipitate. Preparing a Standard Solution by Dilution There is a video demonstration of this technique on the Nelson Web site. www.science.nelson.com Preparation of Standard Solutions Laboratory procedures often call for the use of a solution of specific, accurate concentration. The apparatus used to prepare such a solution is a volumetric flask. A meniscus finder is useful in setting the bottom of the meniscus on the calibration line (Figure 22). GO 1. (Prelab) Calculate the volume of concentrated reagent required. 2. Add approximately one-half of the final volume of pure water to the volumetric flask. 3. Measure the required volume of stock solution using a pipette. (Refer to “Using a Pipette” on page 800). Preparing a Standard Solution from a Solid Reagent 4. Transfer the stock solution slowly into the volumetric There is a video demonstration of this technique on the Nelson Web site. 5. Add pure water, and then use a medicine dropper and www.science.nelson.com NEL GO flask while mixing. a meniscus finder to set the bottom of the meniscus on the calibration line (Figure 22). Technological Problem Solving 803 C Appendix A-F_Chem20 11/1/06 10:37 AM Page 804 6. Stopper and mix the solution by slowly inverting the flask several times. If water is added directly to some solids or concentrated liquids, there may be boiling or splattering. Always add a solid solute or concentrated liquids to water. Titration 0.1 mL. Avoid parallax errors by reading volumes at eye level with the aid of a meniscus finder. 4. Pipette a known volume of the solution of unknown concentration into a clean Erlenmeyer flask. Place a white piece of paper beneath the Erlenmeyer flask to make it easier to detect colour changes. 5. Add an indicator if one is required. Add the smallest Titration is used in the volumetric analysis of an unknown concentration of a solution. Titration involves adding a solution (the titrant) from a burette to another solution (the sample) in an Erlenmeyer flask until a recognizable endpoint, such as a colour change, occurs. (See the video on the Nelson Web site.) www.science.nelson.com 3. Record the initial burette reading to the nearest GO 1. Rinse the burette with small volumes of pure water using a wash bottle. Using a burette funnel, rinse with small volumes of the titrant (Figure 23). (If liquid droplets remain on the sides of the burette after rinsing, scrub the burette with a burette brush. If the tip of the burette is chipped or broken, replace the tip or the whole burette.) quantity necessary (usually 1 to 2 drops) to produce a noticeable colour change in your sample. 6. Add the solution from the burette quickly at first, and then slowly, drop-by-drop, near the endpoint (Figure 24). Stop as soon as a drop of the titrant produces a permanent colour change in the sample solution. A permanent colour change is considered to be a noticeable change that lasts for 10 s after swirling. 7. Record the final burette reading to the nearest 0.1 mL. 8. The final burette reading for one trial becomes the initial burette reading for the next trial. Three trials with results within 0.2 mL are normally required for a reliable analysis of an unknown solution. 9. Drain and rinse the burette with pure water. Store the burette upside down with the stopcock open. Figure 23 A burette should be rinsed with water and then the titrant before use. Figure 24 Near the endpoint, continuous gentle swirling of the solution is particularly important. 2. Using a small burette funnel, pour the titrant solution into the burette until the level is near the top. Open the stopcock for maximum flow to clear any air bubbles from the tip and to bring the liquid level down to the scale. 804 Appendix C NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 805 Appendix C Diagnostic Tests The tests described in Table 1 are commonly used to detect the presence of a specific substance. All diagnostic tests include a brief procedure, some expected evidence, and an interpretation of the evidence obtained. This is conveniently communicated using the format, “If [procedure] and [evidence], then [analysis].” Diagnostic tests can be constructed using any characteristic empirical property of a substance. For example, diagnostic tests for acids, bases, and neutral substances can be specified in terms of the pH of the solutions. For specific chemical reactions, properties of the products that the reactants do not have, such as the insolubility of a precipitate, the production of a gas, or the colour of ions in aqueous solutions, can be used to construct diagnostic tests. If possible, you should use a control to illustrate that the test does not give the same results with other substances. For example, in the test for oxygen, inserting a glowing splint into a test tube that contains only air is used to compare the effect of air on the splint with a test tube in which you expect oxygen has been collected. Communication of Diagnostic Tests The procedure, evidence, and analysis information for a diagnostic test can be communicated in three different formats: • “If ... and ... then ...” statement • table • flowchart Table 1 Some Standard Diagnostic Tests Substance tested Diagnostic test water If cobalt(II) chloride paper is exposed to a liquid or vapour, and the paper turns from blue to pink, then water is likely present. oxygen If a glowing splint is inserted into the test tube, and the splint glows brighter or re-lights, then oxygen gas is likely present. hydrogen If a flame is inserted into the test tube, and a squeal or pop is heard, then hydrogen is likely present. carbon dioxide If the unknown gas is bubbled into a limewater solution, and the limewater turns cloudy, then carbon dioxide is likely present. halogens If a few millilitres of a hydrocarbon solvent is added, with shaking, to a solution in a test tube, and the colour of the solvent appears to be • light yellow-green, then chlorine is likely present • orange, then bromine is likely present • purple, then iodine is likely present acid If strips of blue and red litmus paper are dipped into the solution, and the blue litmus turns red, then an acid is present. base If strips of blue and red litmus paper are dipped into the solution, and the red litmus turns blue, then a base is present. neutral solution If strips of blue and red litmus paper are dipped into the solution, and neither litmus changes colour, then only neutral substances are likely present. neutral ionic solution If a neutral solution is tested for conductivity with a multimeter, and the solution conducts a current, then a neutral ionic substance is likely present. neutral molecular solution If a neutral solution is tested for conductivity with a multimeter, and the solution does not conduct a current, then a neutral molecular substance is likely present. There are thousands of diagnostic tests. You can create some of these using data from the periodic table (on the inside front cover of this book), and from the data tables in Appendix I and on the inside back cover. NEL Technological Problem Solving 805 C Appendix A-F_Chem20 11/1/06 10:37 AM Appendix D Page 806 STS PROBLEM SOLVING Science is a human endeavour, technology has a social purpose, and both have always been part of society. Science and technology together affect society in a myriad of ways. Society also affects science and technology by placing controls on them and expecting solutions to societal problems. When controversial issues related to science and technology arise in our society, there is often heated debate among var- ious special-interest groups. Often, little progress is made because different parties in the debate generally recognize only a single perspective on the issue. Many people now realize that an informed multi-perspective view is more defensible. The following model represents one possible procedure for making an informed decision on a social issue related to science and technology. D.1 STS Decision-Making Model 1. Identify an STS (science–technology–society) issue. Newspapers, magazines, and news broadcasts are sources of current STS issues. However, some issues like acid rain have been current for some time and rarely appear in the news. When identifying an issue for debate, it is convenient to state the issue as a resolution (e.g., “Be it resolved that the use of fossil fuels for heating homes should be eliminated.” ). 2. Design a plan to address the STS issue. Possible designs include individual research, a debate, a townhall meeting (or role-playing), or participation in an actual hearing or on a committee. 3. Identify and obtain relevant information on as many perspectives as possible. An STS issue will always have scientific and technological perspectives. Common perspectives are shown in Table 2. Table 2 Perspectives on STS Issues scientific ethical technological social ecological militaristic economic esthetic political mystical legal emotional D.2 Types of Reports There are many ways to communicate the results of an investigation of an STS issue (Table 3). All methods will require some research about the issue and perspectives on the issue (including positive and negative viewpoints). Some methods can also include alternative solutions and the evaluation of these solutions. Working within a group and brainstorming is a useful process. No matter how the issue will be presented and reported, you need to be well prepared. 806 Appendix D Another perspective is the world view or perspective of Aboriginal peoples. In general, Aboriginal peoples believe that we are an integral part of our environment. Their holistic view includes not only a physical interdependence but also a spiritual one. Information from different perspectives can be obtained from references and through group discussions. There are many sides to every issue. There can be positive and negative viewpoints about the resolution from every perspective. 4. Generate a number of alternative solutions to the STS problem. Some obvious solutions will arise from the resolution. Other creative solutions often arise from a brainstorming session within a group. 5. Evaluate each solution and decide which is best. One method is to rank the value of a particular solution from each perspective. For example, a solution might have little economic advantage and be ranked as 1 on a scale of 1 to 5; the solution might have a significant ecological benefit and be ranked as 5, for a total of 6. A different solution might be judged as 3 from the economic perspective and 1 from the ecological perspective, for a total of 4. The solution with the highest total is likely to be chosen. Although simplistic, this method facilitates evaluation and illustrates the tradeoffs that occur in any real issue. Table 3 STS Investigations and Reports Plan Reporting suggestions individual or group research • written report or poster • multimedia presentation debate • research notes • videotape of the debate role-playing (e.g., town hall meeting) • research notes • videotape of the meeting survey • survey form with tables and graphs newspaper article • published article NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 807 SAFETY KNOWLEDGE AND SKILLS Appendix E E.1 Laboratory Safety Safety is always important in a laboratory or in other settings that feature chemicals or technological devices. It is your responsibility to be aware of possible hazards, to know the rules—including ones specific to your classroom—and to behave appropriately. Always alert the teacher in case of any accident. Alberta Education has an extensive document,“Safety in the Science Classroom,” that deals with hazards and safety. www.science.nelson.com Safety in the laboratory is an attitude and a habit more than it is a set of rules. It is easier to prevent accidents than to deal with the consequences of an accident. Most of the following rules are common sense: • • • • • • • • • • • • • NEL • • • GO General Safety Rules • • Read all directions before doing any laboratory work, and follow all verbal instructions. Know the potential hazards, including the contents and location of MSDS, and the location of all safety equipment. Wear eye protection and lab aprons/coats. Behave responsibly. Avoid sudden or rapid motion that may interfere with someone carrying or working with chemicals. Wear closed shoes (not sandals or bare feet) when working in the laboratory. Place your books, bags, and purses away from the work area. Do not chew gum, eat, drink, or taste anything in the laboratory. Ask for assistance when you are not sure how to do a procedural step. Inform your teacher immediately if any problem or accident occurs. Never attempt any unauthorized or unsupervised experiments. Never handle any chemical with your hands. Use a laboratory scoop or spoon for solids. Never use the contents of a bottle that has no label or an illegible label. Always double check the label to ensure that you are using the chemical needed. Always pour from the side opposite the label. When leaving chemicals in containers, ensure that they are labelled. Do not take any more chemical than needed and never return excess chemicals to their original container. • • • • Hold larger bottles with both hands; one hand on the base. Do not inhale any vapours directly from any container. If smell is to be tested, fan the vapours toward your nose, keeping the container away from underneath your nose. Always use a pipette bulb, and never pipette by mouth. When heating a test tube over a burner, use a test-tube holder with the test tube at an angle, facing away from you and others. Gently move the test tube backwards and forwards through the flame. Clean up all spills, even spills of water, immediately. Clean up your work area at the end of an experiment. Dispose of chemicals appropriately as directed by your teacher. Always wash your hands with soap and water before you leave the laboratory. Do not forget safety procedures when you leave the laboratory. These same rules also apply at home or at work. Glass Safety and Cuts • Never use glassware that is cracked or chipped. Give • • • such glassware to your teacher or dispose of it as directed. Do not put the item back into circulation. Never pick up broken glassware with your fingers. Use a broom and dustpan. Do not put broken glassware into garbage containers. Dispose of glass fragments in special containers marked “broken glass.” If you cut yourself, inform your teacher immediately. Imbedded glass or continued bleeding requires medical attention. Burns • In a laboratory where burners or hot plates are being • used, never pick up a glass object without first checking the temperature by lightly and quickly touching the item. Glass items that have been heated stay hot for a long time but do not appear to be hot. Metal items such as ring stands and hot plates can also cause burns; take care when touching them. Before using a laboratory burner, make sure that long hair is always tied back. Do not wear loose clothing. (Wide long sleeves should be tied back or rolled up.) Safety Knowledge and Skills 807 E Appendix A-F_Chem20 • • • • • 11/1/06 10:37 AM Page 808 Do not use a laboratory burner near wooden shelves, flammable liquids, or any other item that is combustible. Know how to use the type of burner in your laboratory. (See Using a Laboratory Burner, page 798) Never look down the barrel of a laboratory burner. Always pick up a burner by the base, never by the barrel. Never leave a lighted bunsen burner unattended. If you burn yourself, immediately run cold water over the burned area and inform your teacher. Eye Safety • Always wear approved eye protection in a laboratory, • • • • no matter how simple or safe the task appears to be. Keep the safety glasses over your eyes, not on top of your head. For certain experiments, full face protection may be necessary. Never look directly into the opening of flasks or test tubes. If, in spite of all precautions, you get a solution in your eye, quickly use the eyewash station or nearest running water. Continue to rinse the eye with water for at least 15 minutes. This is a very long time—have someone time you. Unless you have a plumbed eyewash system, you will also need assistance in refilling the eyewash container. Have another student inform your teacher of the accident. The injured eye should be examined by a doctor. It is recommended that you do not wear contact lenses in the laboratory. If you wear contact lenses in the laboratory, there is a danger that a chemical might get behind the lens where it cannot be rinsed out with water. If you must wear contact lenses in the chemistry laboratory, be extra careful. Tell your teacher if you are wearing contact lenses in the laboratory. Whether or not you wear contact lenses, do not touch your eyes without first washing your hands. If a piece of glass or other foreign object enters an eye, immediate medical attention is required. Fire Safety Immediately inform your teacher of any fires. Very small fires in a container may be extinguished by covering the container with a wet paper towel or a ceramic square, which would cut off the supply of air. If anyone’s clothes or hair catch fire, the fire can be extinguished by smothering the flames with a blanket or a piece of clothing. Larger fires require a fire extin- 808 Appendix E guisher. (Know how to use the fire extinguisher that is in your laboratory.) If the fire is too large to approach safely with an extinguisher, vacate the location and sound the fire alarm. (School staff will inform the fire department.) If you use a fire extinguisher, direct the extinguisher at the base of the fire and use a sweeping motion, moving the extinguisher nozzle back and forth across the front of the fire’s base. You must use the correct extinguisher for the kind of fire you are trying to control. Each extinguisher is marked with the class of fire for which it is effective. The fire classes are outlined below. Most fire extinguishers in schools are of the ABC type. • • • • • Class A fires involve ordinary combustible materials that leave coals or ashes, such as wood, paper, or cloth. Use water or dry chemical extinguishers on Class A fires. (Carbon dioxide extinguishers are not satisfactory as carbon dioxide dissipates quickly and the hot coals can reignite.) Class B fires involve flammable liquids such as gasoline or solvents. Carbon dioxide or dry chemical extinguishers are effective on Class B fires. (Water is not effective on a Class B fire since the water splashes the burning liquid and spreads the fire.) Class C fires involve live electrical equipment, such as appliances, photocopiers, computers, or laboratory electrical apparatus. Carbon dioxide or dry chemical extinguishers are recommended for Class C fires. Carbon dioxide extinguishers are much cleaner than the dry chemical variety. (Using water on live electrical devices can result in severe electrical shock.) Class D fires involve burning metals, such as sodium, potassium, magnesium, or aluminium. Sand or salt are usually used to put out Class D fires. (Using water on a metal fire can cause a violent reaction.) Class E fires involve a radioactive substance. These involve special considerations at each site. Electrical Safety Water or wet hands should never be used near electrical equipment. When unplugging equipment, remove the plug gently from the socket (do not pull on the cord). Do not use any devices with electric motors when flammable liquids are present unless the area is well ventilated. NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 809 Appendix E E.2 Safety Symbols and Information Educational, Commercial, and Industrial Information Class B: Flammable and combustible material Class A: Compressed gas Class C: Oxidizing material Class D: Poisonous and Infectious Materials Division 1 Division 2 Division 3 Materials causing immediate and serious toxic effect Materials causing other toxic effects Biohazardous infectious material The Workplace Hazardous Materials Information System (WHMIS) provides workers and students with complete and accurate information regarding hazardous products. All chemical products supplied to schools, businesses, and industry must contain standardized labels and be accompanied by Material Safety Data Sheets (MSDS) providing detailed information about the product. Clear and standardized labelling is an important component of WHMIS (Figure 25). These labels must be present on the product’s original container or be added to other containers if the product is transferred. Although MSDS must be supplied with every product sold, current MSDS can also be obtained at several Internet sites, which are useful for researching information about chemicals. www.science.nelson.com Figure 25 WHMIS symbols Class F: Dangerously reactive material Class E: Corrosive material Poison Danger E Flammable Explosive Warning Corrosive Caution GO Consumer Information The Canadian Hazardous Products Act requires manufacturers of consumer products containing chemicals to include a symbol specifying both the nature and degree of the primary hazard, and to note any secondary hazards, first aid treatment, storage, and disposal. The symbols show the hazard by an illustration and the degree of the hazard by the type of border surrounding the illustration (Figure 26). Figure 26 Household Hazardous Product Symbols NEL Safety Knowledge and Skills 809 Appendix A-F_Chem20 11/1/06 10:37 AM Page 810 E.3 Waste Disposal Disposal of chemical wastes at home, at school, or at work is a societal issue. We all need to be stewards of our planet; in other words, to behave as custodians or keepers. Some governments, institutions, and industries have begun to implement product stewardship programs. This is an environmental management plan based on the principle that whoever designs, produces, sells, or uses a product should take responsibility for minimizing the product’s environmental impact over its complete life cycle. Governments have regulations for the handling, transportation, and disposal of chemicals, but each of us needs to take responsibility for the wastes we produce at home and at school. Most laboratory waste can be washed down the drain, or, if it is in solid form, placed in ordinary garbage containers. However, some waste must be treated more carefully. Throughout this textbook, special waste disposal problems are noted, but it is your responsibility to dispose of waste in the safest possible manner. Heavy Metal Solutions Heavy metal compounds (for example, lead, mercury, or cadmium compounds) should not be flushed down the drain. These substances are cumulative poisons and should be kept out of the environment. A special container is kept in the laboratory for heavy metal solutions. Pour any heavy metal waste into this container. Remember that paper towels used to wipe up solutions of heavy metals, as well as filter papers with heavy metal compounds imbedded in them, should be treated as solid toxic waste. Disposal of heavy metal solutions is usually accomplished by precipitating the metal ion (for example, as lead(II) silicate) and disposing of the solid. Disposal may be by elaborate means such as deep well burial, or by simpler but accepted means such as delivering the substance to a landfill. Heavy metal compounds should not be placed in school garbage containers. Usually, waste disposal companies collect materials that require special disposal and dispose of them as required by law. Flammable Substances Flammable liquids should not generally be washed down the drain. (The exceptions to this rule are aqueous solutions of non-toxic flammables such as alcohol–water solutions: they can safely be flushed.) Special fire-resistant containers are used to store flammable liquid waste. Waste solids that pose a fire hazard should be stored in fireproof containers. Care must be taken not to allow flammable waste to come into contact with any sparks, flames, other ignition sources, or oxidizing materials. The particular method of disposal depends on the nature of the substance. Corrosive Solutions Solutions that are corrosive but not toxic, such as acids, bases, or oxidizing agents, can usually be washed down the drain, but care should be taken to ensure that they are properly neutralized and diluted. To neutralize diluted waste acids, use diluted waste bases, and vice versa. Or, use sodium bicarbonate for neutralizing the acid and use dilute hydrochloric acid for neutralizing the base. Oxidizing agents, such as potassium permanganate, should also be diluted with a 10% aqueous solution of sodium thiosulfate (reducing agent) before washing them into the drain. Use large quantities of water and continue to pour water down the drain for a few minutes after all the substance has been washed away. 810 Appendix E Toxic Substances Solutions of toxic substances, such as oxalic acid, should not be poured down the drain, but should be disposed of in the same manner as heavy metal solutions. Solid toxic substances are handled similarly to precipitates of heavy metal. Chemicals should be stored in their original containers, with their labels clearly visible. Appendix A-F_Chem20 11/1/06 10:37 AM Appendix F Page 811 COMMUNICATION SKILLS Communication is essential in science. The international scope of science requires that quantities, chemical symbols, and mathematical tools such as numbers, operations, tables, and graphs, be understood by scientists in different countries with different languages. The way in which scientific knowledge is expressed also reflects the nature of scientific knowledge, and in particular, the certainty of the knowledge. F.1 Scientific Language Science deals with two types of knowledge: empirical (observable “facts”) and theoretical (non-observable ideas). Directly observable knowledge is generally considered to be more certain than interpretations or theoretical concepts. Theories are subject to change and, therefore, are less certain than the observations upon which they are based. When observations are interpreted or explained, the language used should reflect some uncertainty or tentativeness. Use phrases such as • • • • • The evidence suggests that… According to the theory of… It appears likely that… Scientists generally believe that… One could hypothesize that… Avoid the use of the word “prove.” Scientific concepts cannot be proven. The evidence may be extensive and reliable, but a concept to explain the evidence will never be 100% certain. In general, the language that you use should reflect the certainty of the information (observations are more certain than scientific concepts), and it should refer to the evidence available to you. DID YOU KNOW ? Confidence in Empirical versus Theoretical Knowledge A candle does not burn unless air is present. In a closed container, a candle flame is extinguished after a short period of time. These are simple and relatively certain facts that can be directly stated. At one time, scientists believed that burning releases a substance called phlogiston, which was absorbed by the air until it could hold no more phlogiston; this is what stopped the burning. This theory, which was firmly believed by many chemists until the 1800s, was eventually replaced by the oxygen theory of combustion. The facts (evidence) remained the same but the idea (theory) completely changed. F.2 SI Symbols and Conventions The International System of Units, known as SI from the French name, Système international d’unités, is the measurement and communication system used internationally by scientists; it is also the legal measurement system in Canada and most countries in the world. Physical quantities are ultimately expressed in terms of seven fundamental SI units, called base units, which cannot be expressed as combinations of simpler units (Table 4). Although the base unit for mass is the kilogram (kg), it is more common in a chemistry laboratory to use the gram (g). Similarly, although the base unit for temperature (T) is kelvin (K), the common temperature (t) unit is degree Celsius (°C). All other quantities can be expressed in terms of these seven fundamental quantities. For convenience, a unit derived from a combination of base units may be assigned a symbol of its own. Table 5 lists a few of the physical quantities and derived units most commonly encountered in chemistry. NEL Table 4 Quantities and Fundamental Base Units Quantity Symbol Unit Symbol length l metre m time t second s mass m kilogram kg chemical amount n mole mol temperature T kelvin K electric current I ampere A luminous intensity Iv candela cd Quantities and their SI base units are listed in Table 5, on the next page. These are the units most widely used by scientists. For convenience, however, units such as tonne (T) for mass and annum (a) for year are sometimes used to represent quantities that would be inconveniently large when expressed as base units. Communication Skills 811 F Appendix A-F_Chem20 11/1/06 10:37 AM Page 812 Table 5 Quantities and Base Units Quantity Symbol Unit Symbol molar mass M grams per mole g/mol volume V litre L amount concentration c moles per litre mol/L pressure P pascal Pa energy E joule J heat capacity C joules per degree Celsius J/°C specific heat capacity c joules per gram per degree Celsius J/(g•°C) volumetric heat capacity c megajoules per cubic metre per degree Celsius MJ/(m3•°C) molar enthalpy rHm kilojoules per mole kJ/mol enthalpy change rH kilojoules kJ electric charge Q coulomb C electric potential difference (voltage) E volt (joules per coulomb) V SI Prefixes Next to universality, the most important feature of any system of units is convenience. SI has been designed to maximize convenience in a number of ways. A given quantity is always measured in the same base unit regardless of the context in which it is measured. For example, all forms of energy, including energy in food, are measured in joules. When a unit is too large or too small for convenient measurement, the unit is adjusted in size with a prefix. (See Table 6.) Prefixes allow units to be changed in size by multiples of ten. However, except for the use of “centi” in centimetre, we commonly use only prefixes that change the unit in multiples of a thousand. Table 6 Some SI Prefixes Prefix Symbol Fact tera T 1012 giga G 109 mega M 106 kilo k 103 milli m 103 micro m 106 nano n 109 pico p 1012 Scientific Notation the following numbers are expressed in regular notation and scientific notation: Regular notation Scientific notation 1200 L 0.000 000 998 mol/L 1.200 103 L – 9.98 10 7 mol/L On some calculators, the F e E key or the FSE key changes the number in the display into or from scientific notation. To enter a value in scientific notation in your calculator, the EXP or EE key is used to enter the power of ten. Note that the base 10 is not keyed into the calculator. For example, to enter 1.200 × 10 3 press 1 • 2 EXP 3 9.98 × 10 9 • 9 8 EXP –7 press 7 +/– All mathematical operations and functions (such as , –, ×, ÷, log) can be carried out with numbers in scientific notation. Scientific notation is useful in calculations because it simplifies the cancellation of units and the totalling of powers of ten. However, scientific notation is sometimes overused. SI recommends that, wherever possible, prefixes be used to report measured values. Scientific notation should be reserved for situations where no prefix exists, or where it is essential to use the same unit (for example, comparing a wide range of energy values in kilojoules per gram). A reported value should use a prefix or scientific notation, but not both, unless you are comparing values. Scientific notation should usually use the base unit. Scientific notation is a convenient method for expressing either a very large value or a very small value as a number between 1 and 10 multiplied by a power of 10. For example, 812 Appendix F NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 813 Appendix F F.3 Quantitative Descriptions and Rules Quantities that have exact values are either defined quantities (for example, 1 t is defined as exactly 1000 kg, and the SI prefix kilo, k, is exactly 1000), or quantities obtained by counting (for example, 32 people in a class or any coefficient in a balanced chemical equation). You can be certain about such quantities; there will be a small degree of uncertainty when counting very large numbers. On the other hand, most quantities are measured by a person using some measuring instrument (for example, measuring the mass of a chemical using a balance). Since every instrument has its limitations and no one can perfectly measure a quantity, there is always some uncertainty about the number obtained. This uncertainty depends on the size of the sample measured, the particular instrument used, and the technological skill of the person doing the measurement. Accuracy Accuracy is an expression of how close an experimental value is to the accepted value. The comparison of the two values is often expressed as a percent difference. For example, the accuracy of a prediction based on some authority can be expressed as the absolute value of the difference divided by a predicted value and converted to a percent. % difference experimental value predicted value 100 predicted value This expression of accuracy is often used in the Evaluation section of investigation reports. (a) (b) Precision Accuracy is an expression of how close a value is to the accepted, expected, or predicted value, whereas precision is a measure of the reproducibility or consistency of a result (Figure 27). Accuracy is generally attributed to an error in the system (a systematic error); precision is associated with a random error of measurement. For example, if you used a balance without zeroing it, you might obtain measurements that have high precision (reproducibility) but low accuracy. The systematic error might be high (low accuracy), but the random error of the measurement is low (high precision). Scientists define precision as the closeness of the agreement between independent measurements. We make the assumption that, if an instrument produces a certain decimal fraction (like a tenth of a unit), then all repeated measurements would be the same except for that last digit. As long as an instrument is read correctly, for simplicity, we will assume that precision is the place value of the last measurable digit and is determined by the instrument. A mass of 17.13 g is more precise than 17.1 g. The precision is determined by the particular system or instrument used; for example, a centigram balance versus a decigram balance. You may not know how uncertain the last measured digit is. On a centigram balance, the error of measurement in the last digit is usually 0.01 g. Measurements such as 12.39 g, 12.40 g, and 12.41 g all have the same precision (hundredths), and may all be equally correct masses for the same object. The precision with which you read a thermometer might be 0.2 °C (for example, 21.0 °C, 21.2 °C or 21.4 °C) and a ruler might be read to 0.5 mm; you must decide, for example, whether to record 11.0 mm, 11.5 mm, or 12.0 mm. (c) Figure 27 The positions of the darts in each of these figures are analogous to measured or calculated results in a laboratory setting. The results in (a) are precise and accurate, in (b) they are precise but not accurate, and in (c) they are neither precise nor accurate. NEL Communication Skills 813 F Appendix A-F_Chem20 11/1/06 10:37 AM Page 814 Precision Rule for Calculations A result obtained by adding or subtracting measured values is rounded to the same precision (number of decimal places) as the least precise value used in the calculation. For example, 12.6 g 2.07 g 0.142 g totals to 14.812 g on your calculator. This value is rounded to one-tenth of a gram and reported as 14.8 g because the first measurement limits the precision of the final result to tenths of a gram and the rounding rule suggests leaving the 8 as is. The final result is reported to the least number of decimal places in the values added or subtracted. the decimal point. For example, 6.20 mL (3 significant digits) has the same number of significant digits as 0.00620 L. For each of the following measurements, the certainty (number of significant digits) is stated beside the measured or calculated value: 0.41 mL a certainty of 2 significant digits 700 mol a certainty of 3 significant digits 0.020 50 km a certainty of 4 significant digits a certainty of 1 significant digit 2 1040 m Certainty Rule for Calculations Precision Rule for pH The precision rule for pH and pOH is a special case, although the logic is consistent with that for values expressed in scientific notation. A hydrogen or hydronium ion concentration of 1.0 107 mol/L converts to a pH of 7.00. Just as the 7 is not counted as a significant digit when communicating the scientific notation value, the 7 is also not counted when communicating the pH value. Therefore, the rule is • The number of digits following the decimal point in a pH or pOH value is equal to the number of significant digits in the corresponding hydronium or hydroxide ion concentration. and • The number of significant digits in a hydronium or hydroxide ion concentration is equal to the number of digits following the decimal place in the corresponding pH or pOH. Certainty How certain you are about a measurement depends on two factors—the precision of the instrument and the value of the measured quantity. More precise instruments give more certain values; for example, 15.215 °C as opposed to 15 °C. Consider two measurements with the same precision, 0.4 g and 12.8 g. If the balance used is precise to 0.2 g, the value 0.4 g could vary by as much as 50%. However, 0.2 g of 12.8 g is a variation of less than 2%. For both factors—precision of instrument and value of the measured quantity—the more digits in a measurement, the more certain you are about the measurement. We communicate the certainty of any measurement by the number of significant digits. In a measured or calculated value, significant digits are all those digits that are certain plus one estimated (uncertain) digit. Significant digits include all digits correctly reported from a measurement, except leading zeros. Leading zeros are the zeros at the beginning of a decimal fraction and are written only to locate 814 Appendix F Significant digits are primarily used to determine the certainty of a result obtained from calculations using several measured values. A result obtained by multiplying or dividing measured values is rounded to the same certainty (number of significant digits) as the least certain value used in the calculation. For example, 0.024 89 mol 6.94 g/mol is displayed as 0.1727366 g on a calculator. This is correctly reported as 0.173 g or 173 mg because the second value used (6.94) limits the final result to a certainty of three significant digits. Research in the News News media often quote the results of surveys, such as the percentage of people who would vote for a certain political party. What does it mean when we hear, “The results were Yes 52%, No 42%, Undecided 5%, with a margin of error of 3% 19 times out of 20”? The margin of error (3%) is usually calculated as the reciprocal of the square root of the sample size. A larger sample size would therefore produce a smaller margin of error. The confidence level (19 times out of 20) is like the precision. If the survey were repeated 20 times, the result would be within the percent error 19 times and 1 time it would be very different. The pollster, in effect, claims to be (accurate) within 3% of the “real” answer 19 out of 20 times. Rounding When completing calculations that involve more than one step, there are two rules that are used for answers in this textbook: • Never round off partial answers in your calculator. • Always round off when communicating partial answers on paper. When chained calculations involve both multiplication/division and addition/subtraction, you may be required to store the partial answers in your calculator memory or to use the bracket function on your calculator. NEL Appendix A-F_Chem20 11/1/06 10:37 AM Page 815 Appendix F Rounding Rule Calculations are usually based on measurements (for example, in the Analysis section of a report). To report a calculated result correctly, follow this procedure. Check the first digit following the digit that will be rounded. If this digit is less than 5, it and all following digits are discarded. If this digit is 5 or greater, it and all following digits are discarded, and the preceding digit is increased by one. F.4 Tables and Graphs Tables The Reaction of HCl(aq) with Zn(s) F 300 Time (s) Both tables and graphs are used to summarize information and to illustrate patterns or relationships. Preparing tables and graphs requires some knowledge of accepted practice and some skill in designing the table or graph to best describe the information. 200 100 1. Write a descriptive title (Table 7). 2. The row or column with the manipulated variable usually precedes the row or column with the responding variable. 3. Label all rows and/or columns with a heading, including units in parentheses where necessary. Units are not usually written in the main body of the table. Table 7 The Reaction of HCl(aq) with Zn(s) Concentration of HCl(aq) (mol/L) Time for reaction (s) 2.0 70 1.5 80 1.0 144 0.5 258 Graphs 1. Write a descriptive title on the graph and label the axes (Figure 28). • Label the horizontal (x) axis with the name of the manipulated variable and the vertical (y) axis with the name of the responding variable. • Include the unit in parentheses on each axis label, for example, “Time (s).” 2. Assign numbers to the scale on each axis. • As a general rule, the data points should be spread out so that at least one-half of the graph paper is used. NEL 0 0.5 1.0 1.5 2.0 Concentration of HCl(aq) (mol/L) Figure 28 A sample graph • Choose a scale that is easy to read and has equal divisions. Each division (or square) must represent a small simple number of units of the variable; for example, 0.1, 0.2, 0.5, or 1.0. • It is not necessary to have the same scale on each axis or to start a scale at zero. • Do not label every division line on the axis. Scales on graphs are labelled in a way similar to the way scales on rulers are labelled. 3. Plot the data points. • Locate each data point by making a small dot in pencil. When all points are drawn and checked, draw an X over each point, or circle each point in ink. • Be suspicious of a data point that is obviously not part of the pattern. Double-check the location of such points, but do not eliminate the point from the graph if it does not align with the rest. 4. Draw the best-fitting line. • Using a sharp pencil, draw a line that best represents the trend shown by the collection of points. Do not force the line to go through each point. Uncertainty of experimental measurements may cause some of the points to be misaligned. Communication Skills 815 Appendix A-F_Chem20 11/1/06 10:37 AM Page 816 • If the collection of points appears to fall in a straight line, use a ruler to draw the line. Otherwise, draw a smooth curve that best represents the pattern of the points. • • • Since the data points are in ink and the line is in pencil, it is easy to change the position of the line if your first curve does not fit the points to your satisfaction. • Using Your Graph Interpolation is used to find values between measured points on the graph. Extrapolation is used to find values beyond the measured points on a graph. A dotted line on a graph indicates an extrapolation. The scattering of points gives a visual indication of the uncertainty in the experiment. A point that is obviously not part of the pattern may require a remeasurement to check for an error or may indicate the influence of an unexpected variable. Although a graph is constructed using a limited number of measured values, the pattern may be used to extend the empirical information. F.5 Problem-Solving Methods Definition of Terms 2 1.5 mol • ratio: comparison of two numbers; e.g., , 3 1L • proportion: an equality of two ratios; e.g. nNH3 1.5 mol 2. 0 L 1L • conversion factor: a specific type of ratio that is used to convert a quantity from one unit to another unit; e.g., 1000 m 1 km 40.00 g 1 mol or , or 1 km 1000 m 1 mol 40.00 g • formula: a mathematical statement of a relationship using SI and IUPAC symbols and format; e.g., m nM (Note: m n M is not acceptable.) Basic Problem-Solving Methods A stoichiometry example is used to compare the three basic methods. Copper metal is used to recover silver from a silver nitrate solution. Predict the mass of silver obtained from the complete reaction of 50.0 g of copper. Cu(s) 2 AgNO3(aq) → 2 Ag(s) Cu(NO3)2(aq) 50.0 g 63.55 g/mol m 107.87 g/mol nAg 2 0.787 mol 1 nAg 1.57 mol mAg 107.87 g 1.57 mol 1 mol mAg 170 g Formula Method m 50.0 g nCu 0.787 mol M 63. 55 g/mol nrequired 2 nAg 0.787 mol 0.787 mol ngiven 1 1.57 mol mAg nM 1.57 mol 107.87 g/mol 170 g Conversion Factor Methods (a) Step method 1 mol nCu 50.0 g 0.787 mol 63. 55 g 2 nAg 0.787 mol 1.57 mol 1 107.87 g mAg 1.57 mol 170 g mol (b) Full method (“Factor Label”) Proportion Method nCu 1 mol 50. 0 g 63. 55 g 816 Appendix F nCu 0.787 mol 1 mol Cu 2 mol Ag mAg 50.0 g Cu 63.55 g Cu 1 mol Cu 107.87 g Ag 170 g 1 mol Ag NEL Appendix G-I_Chem20 11/1/06 10:43 AM Appendix G Page 817 REVIEW OF CHEMISTRY 20 Your review of Chemistry 20 for Chemistry 30 will be more successful if you study the highlighted Summaries, Sample Problems, and Communication Examples in each chapter. By answering the following questions you will find out where you need to check your understanding before starting Chemistry 30. Unit 1 Chemical Bonding (Chapter 3) 1. Distinguish between the two important types of scientific knowledge. 2. Identify the characteristics of acceptable scientific theories. 3. Explain the octet rule and how it relates to chemical reactivity. 4. Copy and complete the following table. Table 1 Theoretical Descriptions of Selected Elements Element name Lewis Group Number Number Number symbol number of valence of lone of bonding electrons pairs electrons calcium aluminium arsenic (b) Ionic compounds are electrical conductors in molten and aqueous states. 8. Using Lewis symbols and formulas, write the formation equation for each of the following compounds. (a) potassium bromide (b) sodium oxide (c) calcium fluoride 9. Why are chemical formulas for ionic compounds always based the simplest whole number ratio of ions? Is the simplest whole number ratio also used for molecular formulas? Why or why not? 10. Compare ionic and covalent bonds, including how they are formed, according to theory and the nature of the bond. 11. For each of the following molecular formulas, draw the Lewis, structural, and stereochemical formulas, and state the shape around the central atom. oxygen (a) OCl2 (d) HCN bromine (b) SiH4 (e) CH2O neon (c) NCl3 5. (a) State the types of elements expected to react to form compounds containing covalent bonds. (b) State the types of elements expected to react to form compounds containing ionic bonds. (c) Explain your answers to (a) and (b) using the concept of electronegativity. (d) Why is it difficult to predict the type of bonding in some compounds using only electronegativities? 6. The two major types of compounds are ionic and molecular. (a) Compare the naming of these compounds. (b) Given the name of an example of each compound, outline how the chemical formula is obtained. Use specific examples in your answer. 7. Theories are created to explain observations. For each of the following properties of ionic compounds, write a brief theoretical explanation. (a) Ionic compounds are hard solids with high melting and boiling points. NEL 12. Classify each of the molecules represented in the previous question as polar or nonpolar. Justify your answer using the molecular shape and bond dipoles (charge distributions). 13. Methylisocyanate is a toxic pesticide that is manufactured using the following chemical reaction. CS2 CH3NH2 → CH3NCS H2S Rewrite this chemical equation using structural formulas for all reactants and products. 14. Define the three types of intermolecular forces. For each type of force, state how you would know if this type of force is likely present among molecules of a substance. 15. Each of the following four substances is either a liquid at SATP or converted to a liquid by changing the conditions: C3H7F, C3H5(OH)3, C3H7NH2, C3H8 (a) Construct a table to summarize the types of intermolecular forces believed to be present among molecules of each of these substances. (b) Predict the order of boiling points from lowest to highest. Justify your answer. Review of Chemistry 20 817 G Appendix G-I_Chem20 11/1/06 10:43 AM Page 818 16. Why are boiling points often used as an indirect measure of the strength of intermolecular forces among molecules of a substance? 17. Explain each of the following observations in terms of the characteristics of molecules and intermolecular forces. (a) The boiling point of fluorine is significantly less than that of chlorine. (b) Drops of ethanol are attracted to an electrically charged strip. (c) Ice has a regular hexagonal structure. 18. A simple, but useful, distinction that is often made is to classify the water on Earth as either fresh water (as in most lakes and streams) or salt water (as in the oceans). (a) Contrast these two terms from a scientific perspective. (b) How is this distinction useful from a technological perspective? 19. Describe an example in which scientific research led to the development of a new technology. Unit 2 Gases (Chapter 4) 1. List seven ways by which empirical knowledge is communicated. 2. List the three characteristics of acceptable scientific laws and generalizations. 3. Describe one natural phenomenon and one technological product that each depend on the properties of gases. 4. Complete the following statements. (a) At a constant temperature and chemical amount of gas, as the pressure increases, the volume ________. (b) At a constant pressure and chemical amount of gas, as the temperature decreases, the volume ________. (c) At a constant volume and temperature, if the chemical amount of gas inside a container is increased, the pressure ________. 818 Appendix G 5. Choose one of the statements in question 4 and write a general design for an experiment to test the statement. Include the identification of all important variables. 6. For each statement in question 4, sketch a graph of the relationship between the manipulated and responding variables. 7. Convert 95.8 kPa into units of millimetres of mercury and atmospheres. 8. A 1.5 L volume of gas is compressed at a constant temperature from 1.0 atm to 5.0 atm. Calculate the final volume. 9. A balloon can hold 800 mL of air before breaking. A balloon at 4.0 °C containing 750 mL of air is allowed to warm up. Assuming a constant pressure inside the balloon, determine the minimum Celsius temperature when the balloon breaks. 10. A sample of argon gas at 101 kPa and 22.0 °C occupies a volume of 150 mL. If the volume doubles at a temperature of 150 °C, determine the new pressure. 11. Using the kinetic molecular theory, explain Boyle’s and Charles’ laws. 12. Illustrate the law of combining volumes using a simple example. Describe the theory used to explain this law. 13. Many people use propane barbeques for outdoor cooking. Predict the volume of carbon dioxide produced when 15 L of propane completely burns at SATP. 14. Describe and compare the behaviour of real and ideal gases using the kinetic molecular theory. 15. Predict the volume that 25.0 g of oxygen gas would occupy at 22.0 °C and 98.1 kPa. 16. Compare the volume that 0.278 mol of hydrogen would occupy at STP and SATP. 17. An average bungalow requires about 400 kmol of methane per year for space heating. (a) Determine the volume of methane at SATP used in one year. (b) Predict the volume of methane used if the pressure is 98.5 kPa and the temperature is 12.7 °C. NEL Appendix G-I_Chem20 11/1/06 10:43 AM Page 819 Appendix G Unit 3 Solutions, Acids and Bases (Chapters 5 & 6) 1. For each of the following perspectives write a brief statement describing the focus or concern of that point of view. • scientific • technological 10. Explain, in terms of breaking and forming bonds, why the dissolving of substances in water can be either exothermic or endothermic. 11. Compounds may be ionic or molecular and may also be acids, bases, or neutral compounds. • economic (a) Design an experiment to classify the solute in each of a number of different solutions. • ecological (b) Outline the expected results. • political 2. List three topics that are current STS issues. 3. Classify each of the following statements using one of the issue perspectives listed in question 1. All of the statements concern sulfur dioxide emissions. (a) An industry spokesman reported that emissions of sulfur dioxide were within the limits set by environmental legislation. (b) Laboratory research has provided evidence that sulfur dioxide from the combustion of fossil fuels is converted to sulfur trioxide in the presence of oxygen. (c) The cost of ending sulfur dioxide pollution of the atmosphere will be high. The longer we delay facing the problem, the greater will be the cost. (d) Sulfur oxides and their related dissolved acids are particularly damaging to soil microbes, water life forms, plants, building materials, and people. (e) One of the most promising scrubbers to remove sulfur dioxide gas from a smoke stack is the limestone−dolomite process. 4. Compare the goals of science and technology. 5. Describe a homogeneous mixture and provide several examples. 6. Define the two main parts of a solution. State an example using a chemical formula and identity the two parts in words. 7. In the exploration of outer space, scientists usually look for the presence of water as a strong indication of the existence of living things. Briefly explain this statement in terms of solutions and reactions. 8. List at least six examples of manufactured solutions found in the home and six examples of natural solutions found in the environment. NEL 9. Distinguish between electrolytes and non-electrolytes, including examples of types of substances in each category. 12. Write dissociation or ionization equations for the following pure substances dissolving in water. (a) lithium phosphate solid (b) hydrogen chloride gas (c) aluminium sulfate solid 13. For each of the following pure substances, write the formulas for the entities present when each substance is placed in water. (a) Sr(OH)2(s) (d) CH3COOH(l) (b) HNO3(l) (e) AgCl(s) (c) C3H8(g) (f) CH3OH(l) 14. List the three advantages of solutions for technological applications. 15. Suppose you are given four unlabelled beakers, each containing a colourless aqueous solution of one solute. The possible solutions are NaCl(aq), HCl(aq), BaCl2(aq), and CH3Cl(aq). Write a series of diagnostic tests to distinguish each solution from the others. 16. Compare the ways in which solution concentrations are expressed in chemistry labs, consumer products, and environmental studies. 17. A household cleaner contains 12.5 g of sodium hypochlorite in 500 mL of solution. Determine the percentage mass by volume concentration of this solution. 18. A drain cleaner contains 2.75 mol/L sodium hydroxide. Calculate the volume of solution that contains 0.375 mol of sodium hydroxide. 19. A windshield washer solution was prepared by dissolving 100 g of methanol in water to form 2.00 L of solution. Calculate the amount concentration of the solution. Review of Chemistry 20 819 G Appendix G-I_Chem20 11/1/06 10:43 AM Page 820 20. A 0.251 mol/L calcium chloride solution is required for an experiment. (a) Calculate the mass of calcium chloride that needs to be measured. (b) Write a specific procedure for an untrained laboratory technician to prepare this solution. 21. (a) Predict the volume of concentrated, 14.6 mol/L phosphoric acid required to prepare 250 mL of a 0.375 mol/L solution. (b) Write a specific procedure to prepare this solution. 28. Use the modified Arrhenius theory to write chemical equations explaining the following evidence. (a) A vinegar solution is acidic. (b) A baking soda (sodium hydrogen carbonate) solution has a pH of 8. (c) Some muriatic (hydrochloric) acid is neutralized with a lye (sodium hydroxide) solution. 29. A simple window cleaning solution containing 0.25 mol/L ammonia has a pOH of 2.5. (a) Convert the pOH into an amount concentration of hydroxide ions. 22. Calculate the amount concentration of each ion in a 2.1 mol/L solution of iron(III) chloride? (b) Write a balanced chemical equation to explain this basic solution. 23. How does the solubility of solids and gases change as the temperature increases? (c) Is ammonia a strong or weak base? Justify your answer. 24. Excess copper(II) sulfate is added to water in a closed system until no more solute dissolves at a constant temperature. 30. Write a design for an experiment to identify strong and weak acids. Include three different diagnostic tests and identify important controlled variables. (a) Describe some empirical properties of this mixture. (b) Provide a brief theoretical explanation of these properties. 25. Write the acid formula for each of the following substances. (a) aqueous hydrogen bromide (b) aqueous hydrogen sulfite (c) hydrofluoric acid (d) sulfuric acid 26. Copy and complete the following table. Table 2 Hydroxide Concentrations and pHs [H3O+(aq)] (mol/L) pH Acidic/basic/neutral 7 1.0 10 8 3.7 6.23 109 27. The pH of pure water is 7, of carbonated water about 5, and of a cola drink about 3. How many times more acidic is a cola drink than carbonated water and pure water? 31. Polyprotic acids and bases occur naturally and are manufactured for a variety of purposes. (a) Distinguish between monoprotic and polyprotic acids and bases. (b) Using boric acid (aqueous hydrogen borate) as an example, write a series of chemical equations showing successive reactions with water. 32. Most scientists agree that the increasing emission of carbon dioxide into the atmosphere from the burning of fossil fuels is the prime cause of global warming. This problem might be even worse if it were not for the fact that approximately half of the carbon dioxide produced is absorbed by the world’s oceans. However, recent research has shown that this is making the oceans more acidic—about 30% more acidic over the past two hundred years. (a) Use the modified Arrhenius theory to write a chemical equation explaining the increased acidity of the world’s oceans. (b) Scientists are not certain what effect the increased acidity will have. If we assume there will be a problem in the oceans, describe some solutions to reduce the addition of carbon dioxide to the oceans. 33. Using pesticides as an example, summarize the intended and unintended consequences of this chemical technology. 820 Appendix G NEL Appendix G-I_Chem20 11/1/06 10:43 AM Page 821 Appendix G Unit 4 Quantitative Relationships (Chapters 7 & 8) 1. Compare the fields of chemistry and chemical technology. 2. Describe two examples of chemical technologies, used by consumers, that are based on the stoichiometry of chemical reactions. 3. Distinguish between qualitative and quantitative chemical analysis and provide an example of each type of analysis. 4. For each of the following mixtures, write a balanced net ionic equation and identify all spectator ions. All reactant solutions are assumed to be at least 0.10 mol/L in concentration. (a) sodium hydroxide and cobalt(II) chloride solutions (b) silver nitrate and calcium iodide solutions (c) silver nitrate solution and zinc metal (d) hydrochloric acid and solid calcium hydroxide (e) the precipitation of aluminium hydroxide in qualitative analysis 5. In your own words, describe the meaning of stoichiometry. 6. List the three types of stoichiometry and describe how each type is recognized. 7. In general, how do chemical industries use the principles of stoichiometry to maximize yields and minimize waste? 8. In the steel industry, carbon reacts with iron(III) oxide (from iron ore) to produce molten iron and carbon dioxide. (a) Write a complete balanced chemical equation for this reaction. (b) Translate this chemical equation into an English sentence including all chemical amounts and states of matter. (c) Using the coefficients, calculate the mass of each reactant and product in this balanced chemical equation. 9. Predict the mass of lead(II) iodide precipitate that forms when 2.93 g of potassium iodide in solution reacts with excess lead(II) nitrate. 10. In a hard water analysis, a calcium chloride solution is reacted with excess aqueous sodium oxalate to produce 0.452 g of calcium oxalate precipitate. Determine the mass of calcium chloride present in the original solution. 11. Analysis for sulfate ions is usually done by first precipitating barium sulfate from a sample. The filter paper containing the barium sulfate precipitate is then ignited. Carbon from the burnt filter paper then reacts with the barium sulfate as shown in the balanced chemical equation below. BaSO4(s) + 2 C(s) → BaS(s) + 2 CO2(g) (a) Predict the mass of carbon required to react with 1.50 g of barium sulfate precipitate. (b) List the assumptions you have made in this calculation. 12. In a test of the stoichiometric method, an excess of sodium hydroxide solution is reacted with a solution containing 1.50 g of aluminium sulfate. (a) Predict the mass of precipitate expected in this reaction. (b) If the actual yield in this experiment was 0.96 g of precipitate, calculate the percent yield. (c) Outline at least three possible reasons for the discrepancy between the theoretical (predicted) yield and the actual yield. 13. Powdered aluminium metal is one of the fuels used in the solid rocket boosters for the NASA Space Shuttle. What volume of oxygen at SATP is required to react completely with 100 kg of aluminium? 14. A portable hydrogen generator uses the reaction of solid calcium hydride and water to form calcium hydroxide and hydrogen. Determine the volume of hydrogen at 96.5 kPa and 22 °C that can be produced from a 50 g cartridge of CaH2(s). 15. A volumetric analysis shows that it takes 32.0 mL of 2.12 mol/L NaOH(aq) to completely react with 10.0 mL of sulfuric acid from a car battery. Calculate the amount concentration of sulfuric acid in the battery solution. (d) How does the total mass of reactants compare with the total mass of products? What principle does this illustrate? NEL Review of Chemistry 20 821 G Appendix G-I_Chem20 11/1/06 10:43 AM Page 822 16. In a laboratory, silver metal can be recycled to produce silver nitrate by the following reaction. 22. Titration curves are useful in studying the progress of a reaction, such as an acid−base reaction. 3 Ag(s) 4 HNO3(aq) → 3 AgNO3(aq) NO(g) 2 H2O(l) Predict the volume of 15.4 mol/L nitric acid required to react with 1.68 kg of silver metal. 17. Distinguish between limiting and excess reagents. 18. Describe the purpose of using an excess reagent in a quantitative analysis? 19. Calcium carbonate is commonly used in simple antacid products to counteract acidity in the stomach. Suppose you add a 750 mg tablet of calcium carbonate to 200 mL of 0.10 mol/L hydrochloric acid (representing the stomach acid). (a) Sketch a general curve for the titration of a strong base with a strong acid. Label the axes and provide a title for the graph. No numbers are required. (b) Place an “X” on the curve where the reaction is complete. At what pH should this occur? (c) Identify a suitable indicator for any strong base− strong acid titration and justify your answer. (d) Would your answers to (a), (b), and (c) change if a strong acid were titrated with a strong base? Note any differences. (a) Which reactant is in excess and by how much? Give your answer in moles. (b) Predict the mass of calcium chloride formed in this reaction. 20. Complete the Materials and Analysis of the following lab report. Problem What is the amount concentration of an unknown sodium carbonate solution? Design Samples of sodium carbonate solution were titrated with a standardized hydrochloric acid solution using methyl orange as the indicator. Evidence Table 3 Titration of 25.0 mL Samples of Na2CO3(aq) with 0.352 mol/L HCl(aq) Trial 1 2 3 4 Final burette reading (mL) 16.5 31.8 47.0 16.4 Initial burette reading (mL) 0.6 16.5 31.8 1.2 822 Appendix G NEL Appendix G-I_Chem20 11/1/06 10:43 AM Appendix H Page 823 DIPLOMA EXAM PREPARATION You have been preparing for the Diploma Exam throughout your high school career. In your final year, as you work through the Chemistry 30 course, here are some tips that will help you perform as well as you possibly can in the Diploma Exam. • Involve Yourself in Class: Attend class regularly and be active in your learning by asking questions and completing assignments. If you work steadily, there will be no need to try to learn everything just before the exam. • Keep Up-to-Date with Chemistry 30 Material: Schedule a regular review time every week and use this time to organize your notes, review the material, and ask yourself questions about what you have learned. Use the Self Quizzes, Chapter Summaries, and other study aids. • Read and Understand the Scoring Criteria for Diploma Exams: The full scoring criteria for the different types of questions are available in the Biology 30 Information Bulletin found online. Read these criteria carefully and make sure you understand what they mean. www.science.nelson.com GO • Practice Writing Old Exams: Simulate the conditions of the exam to get used to sitting through an entire exam and the time constraints of writing the exam. You will also get used to the types of questions on the exam and, afterward, be able to compare your answers to the scoring criteria. • Read the Instructions: Make sure you read the instructions, directions, and questions very carefully. • Become Familiar with the Types of Questions: Read the information below and practice answering each type of question. There are three types of questions on the Diploma Exam: multiple choice, numerical response, and written response. Multiple Choice Questions Multiple choice questions are a large part of the diploma exam. Most of the multiple choice questions on the diploma exam are context-dependent. The others are called “discrete.” Context-dependent multiple choice questions use information provided in addition to the actual question. Examples of this type of question include questions 10 and 11 in the Unit 2 Review. NEL Use this information to answer questions 9 to 11. The empirical study of gases provided a number of laws that formed the basis for important developments in chemistry such as atomic theory and the mole concept. Statements 1. The volume of a gas varies inversely with the pressure on the gas. 2. Volumes of reacting gases are always in simple, whole number ratios. 3. The volume of a gas varies directly with the absolute temperature of the gas. 4. The volume of a gas varies directly with the absolute temperature and inversely with the pressure. 10. Which statements require that the temperature be a controlled variable? A. 1, 2, 3, and 4 B. 1, 3, and 4 only C. 1 and 2 only D. 3 and 4 only 11. Identify the statement that is best explained by Avogadro’s theory. A. 1 B. 2 H C. 3 D. 4 Discrete multiple choice questions have no additional information or directions, such as questions 1 and 2 in the Chapter 7 Review. 1. A main goal of technology is to A. advance science B. identify problems C. explain natural processes D. solve practical problems 2. In the reaction of aqueous solutions of sodium sulfide and zinc nitrate in a chemical analysis, the spectator ions are A. sodium and nitrate ions B. sulfide and zinc ions C. sodium and zinc ions D. sulfide and nitrate ions Diploma Exam Preparation 823 Appendix G-I_Chem20 11/1/06 10:43 AM Page 824 When answering multiple choice questions: • Try to answer the question before looking at the choices. • Eliminate any choices that are incorrect by crossing them out. • Stay alert for key words: most, least, not one of the following, etc. Negative terms (“Which of the following is not a physical property of a gas?”) will be italicized. Look out for these. • Choose the correct answer on the question sheet and then fill in the corresponding circle on the answer sheet. It is important that you stay aware of time, so that you don’t run out of time to transcribe your answers from the question sheet to the answer sheet. Numerical Response Questions Numerical response questions on the Diploma Exam are clearly indicated with the heading “NUMERICAL RESPONSE.” Examples of these types of questions are clearly marked with the icon “NR” in this textbook. There are four types of numerical response questions on the Diploma Exam. They are • calculation of numerical values, • calculation of numerical values expressed in scientific notation, • selecting numerical responses from diagrams or lists, and • determining the sequence of listed events. Specific instructions for recording the answer to each type of numerical response are given in the instructions of the Diploma Exam, as well as with each question. Read the instructions carefully. • Numerical calculations: This category is fairly straightforward. You have to use the provided data to calculate an answer. The answer is a numerical response with a maximum of four digits (including the decimal point). The first digit of your answer goes in the left-hand box on the answer sheet. Depending on the number of digits in your answer, there may be unfilled boxes to the right. The decimal point, if there is one, occupies one of the boxes. If an answer has a value between 0 and 1, for example 0.25, make sure you record the ‘0’ before the decimal point. 824 Appendix H • Calculations requiring an answer in scientific notation: This category is similar to regular numerical calculations, except that the four digits of the response come from an answer in the form a.b × 10cd. When you have completed your calculation, just write the four digits represented by a, b, c, and d in order. • Numerical responses from diagrams or lists: This category involves selecting numbers (usually representing a term or item from several provided) and writing them in the correct order. • Sequence of numbered events or data: These questions ask you to rearrange variables, events, or data into a specified order. Pay particular attention to the instructions, which might specify, for example, “in order of increasing melting temperature.” Written Response Questions There are two written response questions on the Chemistry 30 Diploma Exam. One written response question is a closedresponse question (which has only one correct response) and the other is an open-response question (which has more than one correct response). Learn to determine which type of question is being asked. Closed response questions have specific questions that must be directly answered. These questions are presented as sections and subsections (question 1. a, b, c, etc.). Open response questions, or unified response questions, typically begin with the phrase “Write a unified response...” The question is asked as a series of bullets, and the answers are written in full sentences. Each bullet must be addressed and combined or “unified” into the answer. When answering written response questions • Carefully read the information box and make sure you fully understand the material and all of the question parts before beginning to answer. • Identify each key piece of information and make notes about the meaning and implications of that information. If it helps, mark key words and phrases. Identify which unit of Chemistry 30 is being addressed. This will help you focus your attention to the correct material. • Identify any irrelevant information. NEL Appendix G-I_Chem20 11/1/06 10:43 AM Page 825 Appendix H • Identify the directing words in the question. These are usually highlighted in bold in the question. The directing words have specific meanings and are indicators of what the graders expect for an answer. Examples of directing words include illustrate, analyze, explain, and predict. A complete list of directing words and their meanings can be found online. These words are also included and defined in the Glossary. In your preparation, refer to the list of meanings for directing words. Make sure that you know what is expected for each directing word. www.science.nelson.com GO • Read the question carefully and ask yourself what you are being asked to do. Write the question out in your own words if there are any doubts. Remember, if you don’t understand the question, you will probably not be able to answer it correctly! • Summarize your answers on scrap paper before writing them on the test answer page. • Once you have answered the question, review your answer and make sure you have addressed all parts of the question. This is especially important for the open response question. Answering Closed Response Questions Closed response questions are often based on a summary of current research or a scenario, and data may be given in graph or table format. There are several parts to the question, but the number of parts depends on the context of the question. An example of a closed response question follows. This one is taken from the Chapter 13 Review. 35. Vanadium is a very versatile element in terms of its reactivity. Vanadium metal reacts with fluorine to form VF5, with chlorine to form VCl4, with bromine to form VBr3, with iodine to form VI2, with oxygen to form V2O5, and with hydrochloric acid to form VCl2. (a) Identify the oxidation states of vanadium in each of these compounds. (b) What interpretation can be made about the oxidizing power of the chemicals that react with vanadium metal? (c) Describe how the oxidation state of vanadium relates to the colours of the compounds formed. (d) Report on some technological applications of vanadium and its compounds. Each section of the question must be answered completely for full marks. The number of marks for the question is given in parentheses. Use this as a guide for how detailed your answer should be. Answering Open Response Questions Open response questions are often based on a situation or scenario. You are generally asked to write an essay-type response, guided by the directing word in the question. Following the initial question are several points. Your responses to these points should be integrated into your answer. 34. For the production of pulp from wood, a variety of methods are used, including mechanical and chemical processes. These have advantages and disadvantages that have been widely debated. Prepare an argument for or against the following statement: “The immediate economic value of using technology to produce a product far outweighs any possible future adverse effects.” Your response should also include • researched information about a variety of mechanical and chemical processes • an evaluation of these processes from technological, economic, and ecological perspectives • reference to redox chemistry You will do best answering these questions if you refer to current scientific advances in your answer, as you address the technological and societal aspects of the question. Try to stay up-to-date on current events by reading the newspaper, science magazines, or reliable science Web sites on a regular basis. Make sure that your answer includes both scientific and technology and society aspects. Write your answer out in full. When you have completed your answer, recheck it against the bullets, making sure all parts of the question have been addressed. The open response questions are scored against two separate scales: a science scale, and a technology and society scale. The scores are: 0 (insufficient), 1 (poor), 2 (limited), 3 (satisfactory), 4 (good) and 5 (excellent). The highest score (5) is given for clear, complete answers that address all of the directing words and give more than one example or piece of information for each bullet in the question. The lowest response (0) is given if the answer does not address the questions presented, or is too brief to assess. Complete examples of closed-response questions are online. www.science.nelson.com NEL GO Diploma Exam Preparation 825 H Appendix G-I_Chem20 11/1/06 10:43 AM Page 826 DATA TABLES Appendix I THERMODYNAMIC PROPERTIES OF SELECTED ELEMENTS* Formula ∆fusHm0 (kJ/mol) ∆vapHm0 (kJ/mol) aluminium Al 10.79 294 argon Ar 1.18 beryllium Be 7.90 Name 6.43 THERMODYNAMIC PROPERTIES OF SELECTED COMPOUNDS* c (J/(g°C)) Name Formula 0.897 ice H2O(s) c (J/(g°C)) — 2.00 0.520 water H2O(l) — 1.825 steam H2O(g) — 480 1.026 ammonia NH3(g) 5.66 23.33 2.06 0.474 methanol CH3OH(l) 3.22 35.21 2.53 B 50.2 bromine Br2 10.57 carbon (graphite) C chlorine Cl2 chromium Cr 21.0 cobalt Co 16.06 377 0.421 copper Cu 12.93 300.4 0.385 fluorine F2 0.51 gallium Ga 5.58 254 0.371 germanium Ge 36.94 334 0.320 gold Au 12.72 324 0.129 Substance air 6.40 6.01 ∆vapHm0 (kJ/mol) 297 boron 117 ∆fusHm0 (kJ/mol) 29.96 — 20.41 339.5 6.62 0.709 0.479 40.65 4.19 — 2.02 ethanol C2H5OH(l) 4.93 38.56 2.44 Freon-12 CCl2F2(g) 4.14 20.1 0.60 *at 101.325 kPa (1 atm) 0.449 0.824 MISCELLANEOUS SPECIFIC AND VOLUMETRIC HEAT CAPACITIES Specific heat capacity, c (J/(g°C)) Volumetric heat capacity, c (MJ/(m3°C)) 1.01 0.0012 4.19 helium He 0.014 0.08 5.193 hydrogen H2 0.12 0.90 14.304 water 4.19 0.214 wood 1.26 — 0.449 glass 0.84 — 0.248 polystyrene 0.30 — 0.129 brick/rock — 1.023 concrete — 2.1 0.479 ethylene glycol (50%) — 3.7 0.140 aluminium 0.897 — 1.030 copper 0.385 — 0.444 tin 0.228 — iodine I2 15.52 iron Fe 13.81 krypton Kr 1.64 lead Pb 4.78 magnesium Mg 8.48 manganese Mn 12.91 mercury Hg 2.29 neon Ne 0.33 41.57 340 9.08 179.5 128 221 59.1 1.71 nickel Ni 17.04 nitrogen N2 0.71 5.57 oxygen O2 0.44 6.82 phosphorus P4 0.66 platinum Pt 22.17 radon Rn 3.25 scandium Sc selenium Se 6.69 silicon Si 50.21 359 0.705 silver Ag 11.28 258 0.235 sulfur S8 1.72 45 0.710 tin Sn 7.17 296.1 0.228 14.1 377.5 12.4 469 18.10 332.7 95.48 1.040 0.918 0.769 0.133 0.094 0.568 0.321 titanium Ti 14.15 425 0.523 tungsten W 52.31 806.7 0.132 uranium U 9.14 417.1 0.116 vanadium V 459 0.489 xenon Xe 2.27 zinc Zn 7.07 21.5 12.57 123.6 1.9 0.158 0.388 * molar enthalpies at 101.325 kPa (1 atm) and specific heat capacities for standard state at SATP 826 Appendix I NEL Appendix G-I_Chem20 11/1/06 10:43 AM Page 827 Appendix I STANDARD MOLAR ENTHALPIES OF FORMATION ∆fH m° ∆fH m° NEL Chemical name Formula acetone aluminium oxide ammonia ammonium chloride ammonium nitrate barium carbonate barium chloride barium hydroxide barium oxide barium sulfate benzene bromine (vapour) butane calcium carbonate calcium chloride calcium hydroxide calcium oxide calcium sulfate carbon dioxide carbon disulfide carbon monoxide chloroethene chromium(III) oxide copper(I) oxide copper(II) oxide copper(I) sulfide copper(II) sulfide 1,2-dichloroethane dinitrogen tetraoxide ethane ethane-1,2-diol ethanoic (acetic) acid ethanol ethene (ethylene) ethyne (acetylene) glucose hexane hydrogen bromide hydrogen chloride hydrogen fluoride hydrogen iodide hydrogen perchlorate hydrogen peroxide hydrogen sulfide iodine (vapour) iron(II) oxide iron(III) oxide iron(II, III) oxide lead(II) bromide lead(II) chloride lead(II) oxide lead(IV) oxide magnesium carbonate magnesium chloride magnesium hydroxide magnesium oxide magnesium sulfate (CH3)2CO(l) Al2O3(s) NH3(g) NH4Cl(s) NH4NO3(s) BaCO3(s) BaCl2(s) Ba(OH)2(s) BaO(s) BaSO4(s) C6H6(l) Br2(g) C4H10(g) CaCO3(s) CaCl2(s) Ca(OH)2(s) CaO(s) CaSO4(s) CO2(g) CS2(l) CO(g) C2H3Cl(g) Cr2O3(s) Cu2O(s) CuO(s) Cu2S(s) CuS(s) C2H4Cl2(l) N2O4(g) C2H6(g) C2H4(OH)2(l) CH3COOH(l) C2H5OH(l) C2H4(g) C2H2(g) C6H12O6(s) C6H14(l) HBr(g) HCl(g) HF(g) HI(g) HClO4(l) H2O2(l) H2S(g) I2(g) FeO(s) Fe2O3(s) Fe3O4(s) PbBr2(s) PbCl2(s) PbO(s) PbO2(s) MgCO3(s) MgCl2(s) Mg(OH)2(s) MgO(s) MgSO4(s) (kJ/mol) –248.1 –1675.7 –45.9 –314.4 –365.6 –1213.0 –855.0 –944.7 –548.0 –1473.2 +49.1 +30.9 –125.7 –1207.6 –795.4 –985.2 –634.9 –1434.5 –393.5 +89.0 –110.5 +37.3 –1139.7 –168.6 –157.3 –79.5 –53.1 –126.9 11.1 –84.0 –454.8 –484.3 –277.6 +52.4 +227.4 –1273.3 –198.7 –36.3 –92.3 –273.3 +26.5 –40.6 –187.8 –20.6 +62.4 –272.0 –824.2 –1118.4 –278.7 –359.4 –219.0 –277.4 –1095.8 –641.3 –924.5 –601.6 -1284.9 Chemical name Formula (kJ/mol) manganese(II) oxide manganese(IV) oxide mercury(II) oxide (red) mercury(II) sulfide (red) methanal (formaldehyde) methane methanoic (formic) acid methanol methylpropane nickel(II) oxide nitric acid nitrogen dioxide nitrogen monoxide nitromethane octane ozone pentane phenylethene (styrene) phosphorus pentachloride phosphorus trichloride (liquid) phosphorus trichloride (vapour) potassium bromide potassium chlorate potassium chloride potassium hydroxide propane silicon dioxide (a–quartz) silver bromide silver chloride silver iodide sodium bromide sodium chloride sodium hydroxide sodium iodide sucrose sulfur dioxide sulfur trioxide (liquid) sulfur trioxide (vapour) sulfuric acid tin(II) chloride tin(IV) chloride tin(II) oxide tin(IV) oxide 2,2,4-trimethylpentane urea water (liquid) water (vapour) zinc oxide zinc sulfide MnO(s) MnO2(s) HgO(s) HgS(s) CH2O(g) CH4(g) HCOOH(l) CH3OH(l) C4H10(g) NiO(s) HNO3(l) NO2(g) NO(g) CH3NO2(l) C8H18(l) O3(g) C5H12(l) C6H5CHCH2(l) PCl5(s) –385.2 –520.0 –90.8 –58.2 –108.6 –74.6 –425.0 –239.2 –134.2 –240.6 –174.1 +33.2 +91.3 –113.1 –250.1 +142.7 –173.5 +103.8 –443.5 PCl3(l) –319.7 PCl3(g) KBr(s) KClO3(s) KCl(s) KOH(s) C3H8(g) SiO2(s) AgBr(s) AgCl(s) AgI(s) NaBr(s) NaCl(s) NaOH(s) NaI(s) C12H22O11(s) SO2(g) SO3(l) SO3(g) H2SO4(l) SnCl2(s) SnCl4(l) SnO(s) SnO2(s) C8H18(l) CO(NH2)2(s) H2O(l) H2O(g) ZnO(s) ZnS(s) –287.0 -393.8 –397.7 –436.5 –424.6 –103.8 –910.7 –100.4 –127.0 –61.8 –361.1 –411.2 –425.6 –287.8 –2226.1 –296.8 –441.0 –395.7 –814.0 -325.1 -511.3 –280.7 –577.6 –259.2 –333.5 –285.8 –241.8 –350.5 –206.0 I • Standard molar enthalpies (heats) of formation are measured at SATP (25 °C and 100 kPa). The values were obtained from The CRC Handbook of Chemistry and Physics. • The standard molar enthalpies of elements in their standard states are defined as zero. Data Tables 827 Appendix G-I_Chem20 11/1/06 10:44 AM Page 828 RELATIVE STRENGTHS OF OXIDIZING AND REDUCING AGENTS SOA Strongest Oxidizing Agents DECREASING STRENGTH OF OXIDIZING AGENTS F2(g) – + PbO2(s) + SO42 (aq) + 4 H (aq) – + MnO4 (aq) + 8 H (aq) 3+ Au (aq) – + ClO4 (aq) + 8 H (aq) Cl2(g) + 2 HNO2(aq) + 4 H (aq) + 2– Cr2O7 (aq) + 14 H (aq) + O2(g) + 4 H (aq) + MnO2(s) + 4 H (aq) – + 2 IO3 (aq) + 12 H (aq) Br2(l) + Hg2 (aq) – ClO (aq) + H2O(l) + Ag (aq) – + 2 NO3 (aq) + 4 H (aq) 3+ Fe (aq) + O2(g) + 2 H (aq) – MnO4 (aq) + 2 H2O(l) I2(s) + Cu (aq) O2(g) + 2 H2O(l) + Cu2 (aq) + 2– SO4 (aq) + 4 H (aq) 4+ Sn (aq) + Cu2 (aq) + S(s) + 2 H (aq) AgBr(s) + 2 H (aq) + Pb2 (aq) + Sn2 (aq) AgI(s) + Ni2 (aq) + Co2 (aq) + H3PO4(aq) + 2 H (l) PbSO4(s) + Se(s) + 2 H (aq) + Cd2 (aq) + Cr3 (aq) 2+ Fe (aq) NO2 (aq) + H2O(l) Ag2S(s) + Zn2 (aq) + Te(s) + 2 H (aq) 2 H2O(l) + Cr2 (aq) Se(s) SO42–(aq) + H2O(l) + Al3 (aq) + Mg2 (aq) + Na (aq) 2+ Ca (aq) + Ba2 (aq) + K (aq) + Li (aq) + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + – 2e – 2e – 5e – 3e – 8e – 2e – 4e – 6e – 4e – 2e – 10 e – 2e – 2e – 2e – e – 2e – e – 2e – 3e – 2e – e – 4e – 2e – 2e – 2e – e – 2e – e – 2e – 2e – 2e e– 2 e– 2 e– 2 e– 2 e– 2 e– 2 e– e– 2 e– e2 e– 2 e– 2 e– 2 e– 2 e– 2 e– 2 e– 3 e– 2 e– e– 2 e– 2 e– e– e– Reducing agents – 2 F (aq) PbSO4(s) + 2 H2O(l) + Mn2 (aq) + 4 H2O(l) Au(s) – Cl (aq) + 4 H2O(l) – 2 Cl (aq) N2O(g) + 3 H2O(l) + 2 Cr3 (aq) + 7 H2O(l) 2 H2O(l) + Mn2 (aq) + 2 H2O(l) I2(s) + 6 H2O(l) – 2 Br (aq) Hg(l) – – Cl (aq) + 2 OH (aq) Ag(s) N2O4(g) + 2 H2O(l) + Fe2 (aq) H2O2(l) MnO2(s) + 4 OH–(aq) – 2 I (aq) Cu(s) – 4 OH (aq) Cu(s) H2SO3(aq) + H2O(l) + Sn2 (aq) + Cu (aq) H2S(aq) – Ag(s) + Br (aq) H2(g) Pb(s) Sn(s) Ag(s) + I–(aq) Ni(s) Co(s) H3PO3(aq) + H2O(l) Pb(s) + SO42–(aq) H2Se(aq) Cd(s) + Cr2 (aq) Fe(s) NO(g) + 2 OH–(aq) 2 Ag(s) + S2–(aq) Zn(s) H2Te(aq) H2(g) + 2 OH–(aq) Cr(s) Se2–(aq) SO32–(aq) + 2 OH–(aq) Al(s) Mg(s) Na(s) Ca(s) Ba(s) K(s) Li(s) E°r (V) +2.87 +1.69 +1.51 +1.50 +1.39 +1.36 +1.30 +1.23 +1.23 +1.22 +1.20 +1.07 +0.85 +0.84 +0.80 +0.80 +0.77 +0.70 +0.60 +0.54 +0.52 +0.40 +0.34 +0.17 +0.15 +0.15 +0.14 +0.07 0.00 –0.13 –0.14 –0.15 –0.26 –0.28 –0.28 –0.36 –0.40 –0.40 –0.41 –0.45 -0.46 –0.69 –0.76 –0.79 –0.83 –0.91 –0.92 –0.93 –1.66 –2.37 –2.71 –2.87 –2.91 –2.93 –3.04 DECREASING STRENGTH OF REDUCING AGENTS Oxidizing agents SRA Strongest Reducing Agents • 1.0 mol/L solutions at 25 °C and 1 atm • Values in this table are taken from The CRC Handbook of Chemistry and Physics. 828 Appendix I NEL Appendix G-I_Chem20 11/1/06 10:44 AM Page 829 Appendix I RELATIVE STRENGTHS OF AQUEOUS ACIDS AND BASES Name Formula Formula Name perchloric acid HClO4(aq) ClO4–(aq) perchlorate ion – very large hydroiodic acid HI(aq) I (aq) iodide ion very large hydrobromic acid HBr(aq) Br–(aq) bromide ion very large hydrochloric acid HCl(aq) Cl–(aq) chloride ion very large sulfuric acid H2SO4(aq) HSO4–(aq) hydrogen sulfate ion – nitric acid HNO3(aq) NO3 (aq) hydronium ion H3O+(aq) H2O(l) water 5.4 x 10–2 oxalic acid HOOCCOOH(aq) HOOCCOO–(aq) hydrogen oxalate ion 1.4 x 10–2 sulfurous acid (SO2 + H2O) H2SO3(aq) HSO3–(aq) hydrogen sulfite ion 1.0 x 10 –2 – nitrate ion 2– hydrogen sulfate ion HSO4 (aq) SO4 (aq) sulfate ion 6.9 x 10–3 phosphoric acid H3PO4(aq) H2PO4–(aq) dihydrogen phosphate ion 5.6 x 10–3 nitrous acid HNO2(aq) NO2–(aq) nitrite ion 7.4 x 10–4 citric acid* H3C6H5O7(aq) H2C6H5O7–(aq) dihydrogen citrate ion* –4 – S T R E N G T H 6.3 x 10 hydrofluoric acid HF(aq) F (aq) 1.8 x 10–4 methanoic acid HCOOH(aq) HCOO–(aq) methanoate ion 1.5 x 10–4 hydrogen oxalate ion HOOCCOO–(aq) OOCCOO2–(aq) oxalate ion 9.1 x 10–5 ascorbic acid H2C6H6O6(aq) HC6H6O6–(aq) hydrogen ascorbate ion –5 fluoride ion – 6.3 x 10 benzoic acid C6H5COOH(aq) C6H5COO (aq) benzoate ion 1.8 x 10–5 ethanoic (acetic) acid CH3COOH(aq) CH3COO–(aq) ethanoate (acetate) ion 1.7 x 10–5 dihydrogen citrate ion* H2C6H5O7- HC6H5O72- hydrogen citrate ion* 4.5 x 10–7 carbonic acid (CO2 + H2O) H2CO3(aq) HCO3–(aq) hydrogen carbonate ion –7 2- 3- O F 4.0 x 10 hydrogen citrate ion* HC6H5O7 C6H5O7 citrate ion* 8.9 x 10–8 hydrosulfuric acid H2S(aq) HS–(aq) hydrogen sulfide ion 6.3 x 10–8 hydrogen sulfite ion HSO3–(aq) SO32–(aq) sulfite ion 6.2 x 10–8 dihydrogen phosphate ion H2PO4–(aq) HPO42–(aq) hydrogen phosphate ion A C I D S –8 – 4.0 x 10 hypochlorous acid HClO(aq) ClO (aq) hypochlorite ion 6.2 x 10–10 hydrocyanic acid HCN(aq) CN–(aq) cyanide ion 5.8 x 10–10 boric acid H3BO3(aq) H2BO3–(aq) dihydrogen borate ion 5.6 x 10–10 ammonium ion NH4+(aq) NH3(aq) ammonia 1.0 x 10 –10 – phenol C6H5OH(aq) C6H5O (aq) phenoxide ion 4.7 x 10–11 hydrogen carbonate ion HCO3–(aq) CO32–(aq) carbonate ion 2.2 x 10–12 hydrogen peroxide H2O2(aq) HO2–(aq) hydrogen peroxide ion 2.0 x 10–12 hydrogen ascorbate ion HC6H6O6–(aq) C6H6O62–(aq) ascorbate ion 4.8 x 10–13 hydrogen phosphate ion HPO42–(aq) PO43–(aq) phosphate ion hydrogen sulfide ion HS (aq) S2–(aq) sulfide ion 1.0 x 10–14 water (55.5 mol/L) H2O(l) OH–(aq) hydroxide ion very small hydroxide ion OH–(aq) O2–(aq) oxide ion 1.3 x 10 –13 – B A S E S D E C R E A S I N G very large 1.0 O F Strongest Acid very large Conjugate base S T R E N G T H SA Acid D E C R E A S I N G Equilibrium constant, Ka (mol/L) SB Strongest Base * The molecular formula representing (triprotic) citric acid has been compressed here to its simplest form for ease of use when writing proton transfer equations. Values in this table are taken from Lange’s Handbook of Chemistry for 25 °C. NEL Data Tables 829 I Appendix G-I_Chem20 11/1/06 Appendix J 10:44 AM Page 830 COMMON CHEMICALS You live in a chemical world. As one bumper sticker asks, “What in the world isn’t chemistry?” Every natural and technologically produced substance around you is composed of chemicals. Many of these chemicals are used to make your life easier or safer, and some of them have life-saving properties. Following is a list of selected common chemicals. The chemicals marked with an asterisk are to be memorized. Common name Recommended name Formula Common use/source acetic acid* acetone* acetylene* ASA (Aspirin®) baking soda* battery acid* bleach bluestone brine* citric acid CFC charcoal/graphite* dry ice* ethylene* ethylene glycol* freon-12 Glauber’s salt glucose* grain alcohol* gypsum lime (quicklime)* limestone* lye (caustic soda)* malachite methyl hydrate* milk of magnesia MSG muriatic acid* natural gas* PCBs potash* road salt* rotten-egg gas* rubbing alcohol sand (silica) slaked lime* soda ash* sugar* table salt* washing soda* vitamin C ethanoic acid propanone ethyne acetylsalicylic acid sodium hydrogen carbonate sulfuric acid sodium hypochlorite copper(II) sulfate—(1/5)-water aqueous sodium chloride 2-hydroxy-1,2,3-propanetricarboxylic acid chlorofluorocarbon carbon carbon dioxide ethene ethane-1,2-diol dichlorodifluoromethane sodium sulfate—(1/10)-water D-glucose; dextrose ethanol (ethyl alcohol) calcium sulfate—water calcium oxide calcium carbonate sodium hydroxide copper(II) hydroxide carbonate methanol (methyl alcohol) magnesium hydroxide monosodium glutamate hydrochloric acid methane polychlorinated biphenyls potassium chloride calcium chloride or sodium chloride hydrogen sulfide propan-2-ol silicon dioxide calcium hydroxide sodium carbonate sucrose sodium chloride sodium carbonate—(1/10)-water ascorbic acid CH3COOH(aq) (CH3)2CO(l) C2H2(g) C6H4COOCH3COOH(s) NaHCO3(s) H2SO4(aq) NaClO(s) CuSO4 •5 H2O(s) NaCl(aq) C3H4OH(COOH)3 CxClyFz(l) ; e.g.,C2Cl2F4(l) C(s) CO2(g) C2H4(g) C2H4(OH)2(l) CCl2F2(l) Na2SO4 •10 H2O(s) C6H12O6(s) C2H5OH(l) CaSO4 •2 H2O(s) CaO(s) CaCO3(s) NaOH(s) Cu(OH)2•CuCO3(s) CH3OH(l) Mg(OH)2(s) NaC5H8NO4(s) HCl(aq) CH4(g) (C6HxCly)2 ; e.g., (C6H4Cl2)2(l) KCl(s) CaCl2(s) or NaCl2(s) H2S(g) CH3CHOHCH3(l) SiO2(s) Ca(OH)2(s) Na2CO3(s) C12H22O11(s) NaCl(s) Na2CO3 •10 H2O(s) H2C6H6O6(s) vinegar nail polish remover cutting/welding torch for pain relief medication leavening agent car batteries bleach for clothing algicide/fungicide water-softening agent in fruit and beverages refrigerant fuel/lead pencils “fizz” in carbonated beverages for polymerization radiator antifreeze refrigerant solar heat storage in plants and blood beverage alcohol wallboard masonry chalk and building materials oven/drain cleaner copper mineral gas-line antifreeze antacid (for indigestion) flavour enhancer in concrete etching fuel in transformers fertilizer melts ice in natural gas for massage in glass making limewater in laundry detergents sweetener seasoning water softener vitamin 830 Appendix J NEL