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Electrochemistry Lesson 5 Predicting Spontaneous Reactions Balancing Half Reactions

Electrochemistry Lesson 5 Predicting Spontaneous Reactions Balancing Half Reactions. Predicting Spontaneous Reactions Using the Standard Reduction Chart Does Au 3+ react with Cl - ? If it does write the spontaneous reaction. The top reaction is written forward- reduction.

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Electrochemistry Lesson 5 Predicting Spontaneous Reactions Balancing Half Reactions

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  1. Electrochemistry Lesson 5 Predicting Spontaneous Reactions Balancing Half Reactions

  2. Predicting Spontaneous Reactions Using the Standard Reduction Chart Does Au3+ react with Cl-? If it does write the spontaneous reaction.

  3. The top reaction is written forward- reduction The bottom reaction is written in reverse- oxidation (Au3+ + 3e- Au(s)) 2 (2Cl- Cl2(g) + 2e-) 3 2Au3+ + 6Cl-3Cl2(g) + 2Au(s)

  4. Does Ag+ react with Br-?

  5. nonspontaneous

  6. Some ionsare on both sidesof the table and are oxidizing or reducing agents. For example: Fe Fe2+ Fe3+ Sn Sn2+ Sn4+ Cu Cu+ Cu2+

  7. Does Sn2+ react with Cr?

  8. Check both spontaneous (Sn2+ + 2e- Sn(s)) 3 (Cr(s) Cr3+ + 3e-) 2 2Cr (s) + 3Sn2+2Cr3+ + 3Sn(s)

  9. Can you keep HCl in a Cu container? Explain!

  10. nonspontaneous

  11. Can you keep HCl in a Cu container? Explain! Yes, nonspontaneous. H+ is a weaker oxidizing agent than Cu2+ and Cu+.

  12. Can you keep HCl in a Zn container? Explain!

  13. Spontaneous- no H+ is a stronger oxidizing agent than Zn2+

  14. Write the spontaneous reaction. 2H+ + 2e- H2(g) Zn(s) Zn2+ + 2e- 2H+ + Zn(s) H2(g) + Zn2+

  15. Can you keep HNO3 in a Au container? Explain!

  16. Can you keep HNO3 in a Au container? Explain! Yes, nonspontaneous. HNO3is a weaker oxidizing agent than Au3+.

  17. Can you keep HNO3 in a Cu container? Explain!

  18. Take the strongest ox agent- higher Take the strongest red agent- lower

  19. Can you keep HNO3 in a Cu container? No, spontaneous. HNO3 is a stronger oxidizing agent than Cu2+. Write the spontaneous reaction. NO3- + 4H+ + 3e- NO(g) + 2H2O x 2 Cu(s) Cu2+ + 2e- x 3 2NO3- + 8H+ + 3Cu(s) 2NO(g) + 4H2O + 3Cu2+

  20. nonspontaneous- both on same side Does Au3+ react with Fe3+?

  21. spontaneous- downhill Does Fe3+ react with Pb?

  22. nonspontaneous- uphill Does Cl2 react with F-?

  23. spontaneousdownhill Does S2O82- react with Pb?

  24. nonspontaneous- uphill Does Cu2+ react with Br-?

  25. spontaneous- downhill Does Br2 react with Sn2+?

  26. nonspontaneous- uphill Does Pb2+ react with Fe2+?

  27. spontaneous- downhill Can you keep HCl in a Fe or a Ag container? HCl → H+ + Cl- Yes 2H+ + 2e-→ H2(g) Fe → Fe2+ + 2e- No 2H+ + Fe → H2(g) + Fe2+

  28. Can you keep HNO3 in a Au or a Ag container? Yes NO3- + 4H+ + 3e-→ NO(g) + 2H2O Ag → Ag+ + e- x 3 No NO3- + 4H+ + 3Ag → NO(g) + 2H2O + 3Ag+

  29. Core Concepts What is reduced and oxidized? What gains or loses electrons? What are the oxidizing and reducing agents? +3+5+5 +3 2H+ + As2O3 + 2NO3- + 2H2O  2H3AsO4 + N2O3 oxidized reduced loses e's gains e's red agent ox agent

  30. Core Concepts Is the following a redox reaction? 1 6 -2 1 -2 1 1 6 -2 1 -2 H2SO4 + 2KOH  K2SO4 + 2H2O Not Redox- no change in Oxidation number

  31. PdCl2 reacts with Mn but not Br-. Rank the oxidizing agentsin decreasing strength. Br2 Br- Pd2+ Pd Rank the reducing agentsin decreasing strength. Mn2+ Mn Mn Pd Br- Br2 Pd2+ Mn2+

  32. Balancing Redox Half Reactions in Acid Solution Cr2O72- → Cr3+ 1.Balance the central atom 2.Balance O by adding H2O 3.Balance H by adding H+ 4. Balance the charge by adding electrons 5. Check charge +6 +12 +6 6e- + + 14H+ 2 + 7H2O most positive side

  33. Balancing Redox Half Reactions in Acid Solution HV2O53- → H2VO3+ 1.Balance the central atom 2.Balance O by adding H2O 3.Balance H by adding H+ 4. Balance the charge by adding electrons 5. Check charge -2 +2 -2 H2O + + H+ 2 + 4e-

  34. Balancing Redox Half Reactions in Acid Solution HBr2O72- → H2BrO2- +7 -2 -2 9e- + + 9H+ 2 + 3H2O

  35. Balancing Redox Half Reactions in Acid Solution • 9e- + HBr2O72- + 9H+ → 2H2BrO2- + 3H2O • To balance in base solution………. • Balance in acid • Add OH- to each side to neutralize H+ • Simplify 9OH- 9OH- 6 9H2O

  36. Balancing Redox Half Reactions in Acid Solution 9e- + HBr2O72- + → 2H2BrO2- + -11 -11 6H2O 9OH-

  37. Balance in alkaline solution. Au + ClO-→ HAuCl42- +5 -2 -2 9H+ + 7e- + 4 + 4H2O

  38. Balance in alkaline solution. + 7e- + Au + 4 ClO-→ HAuCl42- + 4H2O 9H+ 9OH- 9OH- 9H2O

  39. Balance in alkaline solution. 5H2O + 7e- + Au + 4ClO-→HAuCl42- + 9OH- -11 -11

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