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Department of Chemistry CHEM1010 General Chemistry ***********************************************

Department of Chemistry CHEM1010 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel: 931-6325 Email: hzhang@tntech.edu.

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Department of Chemistry CHEM1010 General Chemistry ***********************************************

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  1. Department of Chemistry CHEM1010 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel: 931-6325 Email: hzhang@tntech.edu

  2. CHEM1010/General Chemistry_________________________________________Chapter 8. (L30)-Oxidation and Reduction • Today’s Outline ..Review of three views of oxidation and reduction ..Oxidants and reductants ..Oxygen and oxidizing agents (oxidants) Oxygen Other common oxidants

  3. Chapter 8. (L30)-Oxidation and Reduction • Oxidants and reductants Oxidation and reduction happen together (they are coupled). Example: CuO + H2 = Cu + H2O Cu: +2 0 Cu is reduced H: 0 +1 H is oxidized CuO oxidizes H2, so CuO is the oxidant (oxidizing agent) H2 reduces CuO, so H2 is the reductant (reducing agent)

  4. Chapter 8. (L30)-Oxidation and Reduction • Oxidants and reductants Oxidation and reduction happen together (they are coupled). Example: C + O2 = CO2 C: 0 +4 C is oxidized O: 0 -2 O is reduced O2 oxidizes C, so O2 is the oxidant (oxidizing agent) C reduces O2, C is the reductant (reducing agent)

  5. Chapter 8. (L30)-Oxidation and Reduction • Oxygen: An abundant and essential oxidizing agents (oxidants) ..Oxygen is the most common oxidant. ..Oxygen is essential to life (respiration; generating energy) ..Human body: 65% of body is water by mass, 89% of water is oxygen by mass ..21% of air by volume is oxygen ..Combustion: burning with oxygen, oxidation ..Pure oxygen can be made by liquefying air ..~20 billion kg of oxygen is produced per year in USA ..Oxygen can also cause food spoilage, wood decay, and corrosion.

  6. Chapter 8. (L30)-Oxidation and Reduction • Oxygen: An abundant and essential oxidizing agents (oxidants) ..Oxygen is the common electron acceptor in redox reactions. Example: C + O2 = CO2 (charcoal burning) 2H2 + O2 = 2H2O (H2 and O2 burning) CH4 + 2O2 = CO2 + 2H2O (respiration) 4Fe + 3O2 = 2Fe2O3 (corrosion, rusting)

  7. Chapter 8. (L30)-Oxidation and Reduction • Oxygen: An abundant and essential oxidizing agents (oxidants) ..Reaction of oxygen with other elements. Reaction with metals to form metal oxides Example: 4Fe + 3O2 = 2Fe2O3 2Mg + O2 = 2MgO

  8. Chapter 8. (L30)-Oxidation and Reduction • Oxygen: An abundant and essential oxidizing agents (oxidants) ..Reaction of oxygen with other elements. Reaction with non-metals to form non-metal oxides Example: S + O2 = SO2 C + O2 = CO2

  9. Chapter 8. (L30)-Oxidation and Reduction • Oxygen: An abundant and essential oxidizing agents (oxidants) ..Reaction of oxygen with compounds Example: 2H2S + 3O2 = 2SO2 + 2H2O CS2 + 3O2 = CO2 + 2SO2 ..Ozone formation 3O2 + hv = 2O3

  10. Chapter 8. (L30)-Oxidation and Reduction • Other common oxidizing agents (oxidants) ..Hydrogen peroxide: H2O2, 30% (dangerous), 3% solution is used for mouth cleaning ..Potassium dichromate: K2Cr2O7, a very strong oxidant in acidic conditions, Cr(VI), toxic, carcinogenic (the movie); old breathalyzer test for intoxication (reacts with alcohol) by its color change (orange to green); used to be the glassware cleaning solution ..Potassium permanganate: KMnO4, a very strong oxidant in acidic conditions, Mn(VII), purple; disinfectant ..Chlorine: Cl2, quite strong oxidant; disinfectant, tap water smell, swimming pool (calcium hypochlorite, Ca(OCl)2, pH maintained at 7.2-7.8, if too high, using HCl to lower the pH)

  11. Chapter 8. (L30)-Oxidation and Reduction • Other common oxidizing agents (oxidants) ..Bleaches are oxidizing agents or oxidants. laundry bleaches are usually sodium hypochlorite, NaClO as solution (Purex, Clorox), or Ca(OCl)2 as powder non-chlorine beaches: sodium percarbonate (a mixture of Na2CO3 and H2O2) or sodium perborate (a mixture of NaBO2 and H2O2)

  12. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which is oxidant and reductant, respectively, for the following reaction: 2CO + O2 = 2CO2? (a) O2 is the reductant and CO is the reductant; (b) O2 is the oxidant and CO is the oxidant; (c) O2 is the reductant and CO is the oxidant; (d) O2 is the oxidant and CO is the reductant.

  13. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which is the oxidant in the following reaction: 2H2S + 3O2 = 2SO2 + 2H2O? (a) H2O; (b) H2S; (c) O2; (d) SO2.

  14. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which is the reductant in the following reaction: 2H2S + 3O2 = 2SO2 + 2H2O? (a) H2O; (b) H2S; (c) O2; (d) SO2.

  15. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which is the reductant in the following reaction: Se + O2 = SeO2? (a) H2O; (b) Se; (c) O2; (d) SeO2.

  16. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which is the oxidant in the following reaction: Se + O2 = SeO2? (a) H2O; (b) Se; (c) O2; (d) SeO2.

  17. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which of the following is the oxidant? (a) H2O; (b) Fe; (c) KMnO4; (d) H2.

  18. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which of the following is the oxidant? (a) H2O; (b) Fe; (c) K2Cr2O7; (d) H2.

  19. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which of the following is the oxidant? (a) H2O; (b) Zn; (c) H2O2; (d) H2.

  20. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which of the following is the oxidant? (a) H2O; (b) CH4; (c) NaClO; (d) H2.

  21. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which of the following is the oxidant? (a) H2O; (b) CH4; (c) Ca(ClO)2; (d) H2.

  22. Chapter 8. (L30)-Oxidation and Reduction Quiz Time Which is one of the major component of laundry bleaches? (a) O2; (b) CH4; (c) NaOCl or Ca(ClO)2; (d) H2.

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