1. Homework 21-1 Do REVIEW & PRACTICE, page 621 HEATH text, questions #1-4. 21-1 Do REVIEW & PRACTICE, page 621 HEATH text, questions #1-4. Optional: Read HEBDEN WORKBOOK Section 5-1 "Introduction". Do Exercises p.192 #1-2. Optional: Read HEBDEN WORKBOOK Section 5-1 "Introduction". Do Exercises p.192 #1-2. 21-2. Do REVIEW & PRACTICE, page 627 HEATH text, questions #1-4. 21-2. Do REVIEW & PRACTICE, page 627 HEATH text, questions #1-4. 3. Optional: Read HEBDEN WORKBOOK Section 5-2 "Oxidation Numbers". Do Exercise p.194 #3-5. 3. Optional: Read HEBDEN WORKBOOK Section 5-2 "Oxidation Numbers". Do Exercise p.194 #3-5. 4. Do HANDOUT "Section 211/212 Provincial Exam Questions". 4. Do HANDOUT "Section 211/212 Provincial Exam Questions".

2. 21-1 Prov. Exam Answers 1.C 6. C 1.C 6. C 2. D7. C 2. D7. C 3. B8. C 3. B8. C 4. A9. B 4. A9. B 5. A10. A 5. A10. A Written: 1) oxidation = loss of electrons Written: 1) oxidation = loss of electrons reduction =gain of lost electrons reduction =gain of lost electrons Occurs simultaneously

3. 21-2 Prov. Exam Answers 1. B9. C17. A 1. B9. C17. A 2. B10. A18. B 2. B10. A18. B 3. B11. C19. A 3. B11. C19. A 4. D12. A20. C 4. D12. A20. C 5. C13. D21. B 5. C13. D21. B 6. D14. A22. B 6. D14. A22. B 7. B15. C23. D 7. B15. C23. D 8. D16. A24. C 8. D16. A24. C 25. B 26. C 27. C 28. B 29. A 30. A

4. 21-2 Prov. Exam Answers 25. B 25. B 26. C 26. C 27. C 27. C 28. B 28. B 29. A 29. A 30. A 30. A

5. Any Questions? 21-1 8,5 21-1 8,5 21-2 2,5, 7,9,20 21-2 2,5, 7,9,20

6. 21-3 Balancing Redox Reactions – Using Half Reactions a) Half Reactions a) Half Reactions Sample 1:Co +2 ssd Co “unbalanced” Sample 1:Co +2 ssd Co “unbalanced” Oxidation or reduction? Oxidation or reduction? Co +2 + 2e – ssd Co “balanced” Co +2 + 2e – ssd Co “balanced” Reduction!! Reduction!!

7. Sample 2 NO ssd N 2 O “unbalanced” Sample 2 NO ssd N 2 O “unbalanced” Oxidation or reduction? 2NO + 2H + + 2e – ssd N 2 O + H 2 O “balanced” 2NO + 2H + + 2e – ssd N 2 O + H 2 O “balanced”Reduction!!

8. i) Half reactions must be balanced for charge and mass i) Half reactions must be balanced for charge and mass ii) MAJOR OH – (memory aid) ii) MAJOR OH – (memory aid) 1 st balance major atoms (other than O or H), 1 st balance major atoms (other than O or H), 2 nd balance oxygen using water, 2 nd balance oxygen using water, 3 rd balance hydrogen using H + 3 rd balance hydrogen using H + 4 th balance charge (-) using e – 4 th balance charge (-) using e –

9. iii) Balance NO ssd N 2 O (acidic) iii) Balance NO ssd N 2 O (acidic) 1 st Balance for atoms other than O and H 1 st Balance for atoms other than O and H 2NO ssd N 2 O 2NO ssd N 2 O 2 nd Add water to balance O 2 nd Add water to balance O 2NO ssd N 2 O + H 2 O 2NO ssd N 2 O + H 2 O 3 rd Add H + to balance H 3 rd Add H + to balance H 2NO + 2H + ssd N 2 O + H 2 O 2NO + 2H + ssd N 2 O + H 2 O

10. 4 th Add e – to balance charge 4 th Add e – to balance charge 2NO + 2H + + 2e – ssd N 2 O + H 2 O 2NO + 2H + + 2e – ssd N 2 O + H 2 O Check: 2N’s 2”O”’s 2H’s and charge balances Check: 2N’s 2”O”’s 2H’s and charge balances

11. iv) Balance MnO 4 – ssd Mn +2 (acidic) 1 st Balance for atoms other than O and H 1 st Balance for atoms other than O and H MnO 4 – ssd Mn +2 (Mn already balanced) MnO 4 – ssd Mn +2 (Mn already balanced) 2 nd Add water to balance O 2 nd Add water to balance O MnO 4 – ssd Mn +2 + 4H 2 O MnO 4 – ssd Mn +2 + 4H 2 O 3 rd Add H + to balance H 3 rd Add H + to balance H MnO 4 – + 8H + ssd Mn +2 + 4H 2 O MnO 4 – + 8H + ssd Mn +2 + 4H 2 O

12. 4th Add e – to balance charge 4th Add e – to balance charge MnO 4 – + 8H + + 5e – ssd Mn +2 + 4H 2 O MnO 4 – + 8H + + 5e – ssd Mn +2 + 4H 2 O Check: 1 Mn, 4 “O” ‘s, 8 H’s, and charge of +2 on each side. Check: 1 Mn, 4 “O” ‘s, 8 H’s, and charge of +2 on each side.

13. v) Acidic vs. Basic solutions Acidic – proceed as above Acidic – proceed as above Basic – Has some Bonus steps: Basic – Has some Bonus steps: 3a) AFTER balancing H +, for each H + present, add an equal number of OH – ions to BOTH sides; 3a) AFTER balancing H +, for each H + present, add an equal number of OH – ions to BOTH sides; 3b) combine H + and OH – present to form H 2 O; 3b) combine H + and OH – present to form H 2 O; 3c) cancel out water on both sides (and then proceed to step 4– electrons) 3c) cancel out water on both sides (and then proceed to step 4– electrons)

14. vi) Balance Cl 2 sd ClO 3 – (basic) 1 st Balance for atoms other than O and H 1 st Balance for atoms other than O and H Cl 2 ssd ClO 3 – 2 nd Add water to balance O 2 nd Add water to balance O Cl 2 ssd 2ClO 3 – Cl 2 ssd 2ClO 3 – 3 rd Add H + to balance H 3 rd Add H + to balance H Cl 2 + 6H 2 O ssd 2ClO 3 – Cl 2 + 6H 2 O ssd 2ClO 3 – 2 + 6H 2 O + 12H +

15. 3 A) Bonus: Add OH –, equal to H + on both sides 3 A) Bonus: Add OH –, equal to H + on both sides Cl 2 + 6H 2 O ssd 2ClO 3 – + 12H + Cl 2 + 6H 2 O ssd 2ClO 3 – + 12H + B) Combine H + and OH – B) Combine H + and OH – Cl 2 + 6H 2 O + 12OH – ssd 2ClO 3 – Cl 2 + 6H 2 O + 12OH – ssd 2ClO 3 – C) Cancel out H 2 O on both sides C) Cancel out H 2 O on both sides Cl 2 + 12OH – ssd 2ClO 3 – Cl 2 + 12OH – ssd 2ClO 3 – 4 th step Add e – to balance charge 4 th step Add e – to balance charge Cl 2 + 12OH – ssd 2ClO 3 – + 6H 2 O Cl 2 + 12OH – ssd 2ClO 3 – + 6H 2 O + 12 OH – + 6H 2 O + 10e – + 12H 2 O 6

16. HW 21-3 half reactions Do written first #2,3,8 to practice MC #1,2,4,7,11(tough)

17. b) Full Redox Reactions i) Procedure:  Separate redox into its two half reactions  Balance each half reaction as above  Make e– the same for both half reactions (electrons gained = electrons lost)  Add the two half reactions together (cancel out species common to both sides)

18. i) i)Balance in acidic sol n Cu +2 + Al (s) ssd Cu (s) + Al +3 1 st Separate half reactions Cu +2 ssd Cu (s) Al (s) ssd Al +3 2 nd Balance half reactions Cu +2 + 2e – ssd Cu (s) Al (s) ssd Al +3 + 3e –

19. 3rd Make e – the same 3( Cu +2 + 2e – ssd Cu (s) ) 3 Cu +2 + 6e – ssd 3Cu (s) 2(Al (s) ssd Al +3 + 3e – ) 2Al (s) ssd 2Al +3 + 6e –

20. 4th Add half reactions together 3Cu +2 + 6e– ssd 3Cu (s) 2Al (s) ssd 2Al +3 + 6e– 3Cu +2 + 2Al (s) ssd 3Cu (s) + 2Al +3

21. iii) Cr 2 O 7 –2 ssd Cr +3 Cr 2 O 7 –2 ssd 2 Cr +3 Cr 2 O 7 –2 ssd 2 Cr +3 + 7H 2 O Cr 2 O 7 –2 + 14H + ssd 2 Cr +3 + 7H 2 O Cr 2 O 7 –2 + 14H + +6e- ssd 2 Cr +3 + 7H 2 O Fe +2 ssd Fe +3 Fe +2 ssd Fe +3 + 1e -

22. Combine Cr 2 O 7 –2 + 14H + +6e - ssd 2 Cr +3 + 7H 2 O 6Fe +2 ssd 6Fe +3 + 6e - Cr 2 O 7 –2 + 14H + + 6Fe +2 ssd 2 Cr +3 + 7H 2 O + 6Fe +3 Check charge: -2 + 14 + 12 = +24 LHS +6+18= +24 RHS yay

23. MnO 4 – ssd Mn +2 MnO 4 – ssd Mn +2 +4H 2 O MnO 4 – +8H + ssd Mn +2 +4H 2 O MnO 4 – +8H + +5e - ssd Mn +2 +4H 2 O SO 2 ssd SO 4 –2 SO 2 +2H 2 Ossd SO 4 –2 SO 2 +2H 2 Ossd SO 4 –2 + 4H + SO 2 +2H 2 Ossd SO 4 –2 + 4H + + 2e -

24. (MnO 4 – +8H + +5e - ssd Mn +2 +4H 2 O) (SO 2 +2H 2 Osd SO 4 –2 + 4H + + 2e - ) 2MnO 4 – +16H + +10e - ssd 2Mn +2 +8H 2 O) 5SO 2 +10H 2 O ssd 5SO 4 –2 + 20 H + + 10e - ) 2 5

25. (MnO 4 – +8H + +5e - ssd Mn +2 +4H 2 O) (SO 2 +2H 2 Osd SO 4 –2 + 4H + + 2e - ) 2MnO 4 – +16H + +10e - ssd 2Mn +2 +8H 2 O) 5SO 2 +10H 2 O ssd 5SO 4 –2 + 20H + + 10e - ) 2MnO 4 – +5SO 2 +2H 2 Osd2Mn +2 + 5SO 4 –2 + 4H + Check Charge: -2 + 0 = -2 LHS +4 -10 +4 = -2 RHS YAY! 4 2 2 5

26. What if the last reaction was in Base? JUST FOLLOW THIS, DON’T WRITE IT!@

27. MnO 4 – ssd Mn +2 MnO 4 – ssd Mn +2 +4H 2 O MnO 4 – +8H + ssd Mn +2 +4H 2 O MnO 4 – +8H + + 8OH - ssd Mn +2 +4H 2 O + 8OH - MnO 4 – +8H 2 O ssd Mn +2 +4H 2 O+ 8OH - MnO 4 – +4H 2 O ssd Mn +2 +8OH - MnO 4 – +4H 2 O + 5e - ssd Mn +2 +8OH -

28. SO 2 ssd SO 4 –2 SO 2 +2H 2 Ossd SO 4 –2 SO 2 +2H 2 Ossd SO 4 –2 + 4H + SO 2 +2H 2 O+ 4OH - sd SO 4 –2 + 4H + + 4OH - SO 2 +2H 2 O+ 4OH - sd SO 4 –2 + 4H 2 O SO 2 + 4OH - sd SO 4 –2 + 2H 2 O SO 2 + 4OH - sd SO 4 –2 + 2H 2 O+ 2e -

29. NOW LCM of 10 NOW LCM of 10 MnO 4 – +4H 2 O + 5e - ssd Mn +2 +8OH - SO 2 + 4OH - sd SO 4 –2 + 2H 2 O+ 2e - And multiply and cancel and add up etc… LOTS OF WORK… or you could be smart and…

30. Do the equation in acid as before…… 2MnO 4 – +16H + +10e - ssd 2Mn +2 +8H 2 O 5SO 2 +10H 2 O ssd 5SO 4 –2 + 20H + + 10e - 2MnO 4 – +5SO 2 +2H 2 Osd2Mn +2 + 5SO 4 –2 + 4H + 4 2

31. NOW change to base...! 2MnO 4 – +5SO 2 +2H 2 Osd2Mn +2 + 5SO 4 –2 + 4H + + 4OH - + 4OH - 2MnO 4 – +5SO 2 +2H 2 Od2Mn +2 + 5SO 4 –2 + 4H 2 O + 4OH - 2MnO 4 – +5SO 2 +4OH - d2Mn +2 + 5SO 4 –2 + 2H 2 O Check Charge: -2 -4 = -6 LHS +4 -10 = -6 RHS YAY!

32. FOR FULL REDOX REACTIONS IN BASE: Change to base AFTER balancing everything in acid! FOR FULL REDOX REACTIONS IN BASE: Change to base AFTER balancing everything in acid!