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Redox Chemistry Oxidation and Reduction Electrochemistry

Redox Chemistry Oxidation and Reduction Electrochemistry . Syllabus Statements, First Exams 2009. 9.1.1 Define oxidation and reduction in terms of electron loss and gain. 9.1.2 Deduce the oxidation number of an element in a compound.

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Redox Chemistry Oxidation and Reduction Electrochemistry

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  1. Redox ChemistryOxidation and ReductionElectrochemistry

  2. Syllabus Statements, First Exams 2009 9.1.1 Define oxidation and reduction in terms of electron loss and gain. 9.1.2 Deduce the oxidation number of an element in a compound. 9.1.3 State the names of compounds using oxidation numbers. 9.1.4 Deduce whether an element undergoes oxidation or reduction in reactions using oxidation numbers. 9.2.1 Deduce simple oxidation and reduction half-equations given the species involved in a redox reaction. 9.2.2 Deduce redox equations using half equations. 9.2.3 Define the terms oxidizing agent and reducing agent.

  3. Reactions Did the charge on any of the species in this reaction change? e.g. What charge did K start with? Finish with? What charge did Pb start with? Finish with? Precipitation: cations and anions come together to form insoluble ionic compounds. Equation 2 KI (aq) + Pb(NO3)2(aq)  PbI2(s) + 2 KNO3(aq) Complete Ionic Equation 2 K+(aq) + 2 I-(aq) + Pb2+(aq) + 2 NO3-(aq)  PbI2(s) + 2 K+(aq) + 2 NO3-(aq) Net Ionic Equation 2 I-(aq) + Pb2+(aq) +  PbI2(s)

  4. Reactions Did the charge on any of the species in this reaction change? YES! Single-replacement reactions: One metallic element replaces another metallic element in a salt. Equation 3 CuCl2(aq) + 2 Al (s) 2 AlCl3(aq) + 3 Cu (s) Complete Ionic Equation 3 Cu2+(aq) + 6 Cl-(aq) + 2 Al (s) 2 Al3+ (aq) + 6 Cl-(aq) + 3 Cu (s) Net Ionic Equation 3 Cu2+(aq) + 2 Al (s) 2 Al3+ + 3 Cu (s)

  5. Electrochemical Reactions In electrochemical reactions, electrons are transferred from one species to another. Translation: Redox reactions involve the gaining and losing of electrons.

  6. Oxidation Numbers In order to keep track of what loses electrons and what gains them, we assign oxidation numbers.

  7. Assigning Oxidation Numbers Use the chart given and identify the oxidation state of nitrogen in each of the compounds/ions given.

  8. Examples… -3 -2 0 +1 +2 +4 +5 How’d you do? Any questions?

  9. Oxidation • A species is oxidized when it loses electrons. • Here, zinc loses two electrons to go from neutral zinc metal to the Zn2+ ion.

  10. Oxidation and Reduction • A species is reduced when it gains electrons. • Here, each of the H+ gains an electron and they combine to form H2.

  11. LEO the lion goes GER Loss of Electrons is Oxidation Gain of Electrons is Reduction Mnemonic Device

  12. OIL RIG Oxidation Is Loss (of electrons) Reduction Is Gain (of electrons)

  13. King Phillip Came Over For Great Supper Kingdom Phylum Class Order Family Genus Species

  14. Oxidation and Reduction • What is reduced is the oxidizing agent. • H+ oxidizes Zn by taking electrons from the zinc, being reduced in the process. • What is oxidized is the reducing agent. • Zn reduces H+ by giving it electrons, being oxidized in the process.

  15. Example Reaction Identify the following: Element oxidized Element reduced Oxidizing agent Reducing agent 2 PbS (s) + 3 O2 (g)  2 PbO (s) + 2 SO2 (g)

  16. Example Reaction Identify the following: Element oxidized Sulfur Element reduced Oxidizing agent Reducing agent 2 PbS (s) + 3 O2 (g)  2 PbO (s) + 2 SO2 (g)

  17. Example Reaction Identify the following: Element oxidized Sulfur Element reduced Oxygen Oxidizing agent Reducing agent 2 PbS (s) + 3 O2 (g)  2 PbO (s) + 2 SO2 (g)

  18. Example Reaction Identify the following: Element oxidized Sulfur Element reduced Oxygen Oxidizing agent O2 (g) Reducing agent 2 PbS (s) + 3 O2 (g)  2 PbO (s) + 2 SO2 (g)

  19. Example Reaction Identify the following: Element oxidized Sulfur Element reduced Oxygen Oxidizing agent O2 (g) Reducing agent PbS (s) 2 PbS (s) + 3 O2 (g)  2 PbO (s) + 2 SO2 (g)

  20. Example Reaction Identify the following: Element oxidized Element reduced Oxidizing agent Reducing agent Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)

  21. Example Reaction Identify the following: Element oxidized Magnesium Element reduced Oxidizing agent Reducing agent Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)

  22. Example Reaction Identify the following: Element oxidized Magnesium Element reduced Copper Oxidizing agent Reducing agent Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)

  23. Example Reaction Identify the following: Element oxidized Magnesium Element reduced Copper Oxidizing agent CuSO4 (aq) Reducing agent Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)

  24. Example Reaction Identify the following: Element oxidized Magnesium Element reduced Copper Oxidizing agent CuSO4 (aq) Reducing agent Mg (s) Mg (s) + CuSO4 (aq)  MgSO4 (aq) + Cu (s)

  25. Another Example Reaction 5Fe2+(aq) +MnO4- (aq) +8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Identify the following: Element oxidized Element reduced Oxidizing agent Reducing agent

  26. Another Example Reaction 5Fe2+(aq) +MnO4- (aq) +8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Identify the following: Element oxidized Fe2+ Element reduced Oxidizing agent Reducing agent

  27. Another Example Reaction 5Fe2+(aq) +MnO4- (aq) +8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Identify the following: Element oxidized Fe2+ Element reduced Mn Oxidizing agent Reducing agent

  28. Another Example Reaction 5Fe2+(aq) +MnO4- (aq) +8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Identify the following: Element oxidized Fe2+ Element reduced Mn Oxidizing agent MnO4- (aq) Reducing agent

  29. Another Example Reaction 5Fe2+(aq) +MnO4- (aq) +8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) Identify the following: Element oxidized Fe2+ Element reduced Mn Oxidizing agent MnO4- Reducing agent Fe2+

  30. Reactivity Series Some metals make better reducing agents than other metals. (In other words, some metals are oxidized easier.) Let’s look at two reactions: Mg (s) + CuCl2(aq) ??? Mg (s) + NaCl(aq)  ???

  31. Reactivity Series Mg (s) + CuCl2(aq) MgCl2 (aq) + Cu (s) Mg (s) + NaCl(aq)  ???

  32. Reactivity Series Mg (s) + CuCl2(aq) MgCl2 (aq) + Cu (s) Mg (s) + NaCl(aq)  NR

  33. Reactivity Series Mg (s) + CuCl2(aq) MgCl2 (aq) + Cu (s) Mg (s) + NaCl(aq)  NR Activity Series:

  34. Reactivity Series Mg (s) + CuCl2(aq) MgCl2 (aq) + Cu (s) Mg (s) + NaCl(aq)  NR Activity Series: Na > Mg > Cu

  35. Reactivity Series Some halogens make better reducing agents than other halogens. (In other words, some halogens are oxidized easier.) Let’s look at two reactions: F2(g) + NaCl(aq)  ??? Br2(l)+ NaCl(aq)  ???

  36. Reactivity Series Let’s look at two reactions: F2(s) + 2 NaCl(aq)  2 NaF + Cl2 Br2(s) + NaCl(aq)  ???

  37. Reactivity Series Let’s look at two reactions: F2(s) + 2 NaCl(aq)  2 NaF + Cl2 Br2(s) + NaCl(aq)  NR

  38. Reactivity Series Let’s look at two reactions: F2(s) + 2 NaCl(aq)  2 NaF + Cl2 Br2(s) + NaCl(aq)  NR Activity Series:

  39. Reactivity Series Let’s look at two reactions: F2(s) + 2 NaCl(aq)  2 NaF + Cl2 Br2(s) + NaCl(aq)  NR Activity Series: F > Cl > Br What does that resemble?

  40. Halogens F Most Reactive Cl Br I Least Reactive

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