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Electrochemistry III

Electrochemistry III. QUESTION. Meals Ready to Eat (MREs) were developed during the Vietnam War. They need hot water to be reconstituted. The military includes a small packet of metal to heat the water through an oxidation-reduction reaction. Which metal do you think is in the packet?.

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Electrochemistry III

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  1. Electrochemistry III

  2. QUESTION Meals Ready to Eat (MREs) were developed during the Vietnam War. They need hot water to be reconstituted. The military includes a small packet of metal to heat the water through an oxidation-reduction reaction. Which metal do you think is in the packet? • Copper B) Zinc C) Magnesium • D) Manganese E) Iron

  3. Answer Meals Ready to Eat (MREs) were developed during the Vietnam War. They need hot water to be reconstituted. The military includes a small packet of metal to heat the water through an oxidation-reduction reaction. Which metal do you think is in the packet? • Copper B) Zinc C) Magnesium • Reduction of water is -0.83V; magnesium Eored= -2.37V • D) Manganese E) Iron

  4. Electrochemistry Electrochemical Processes in Batteries

  5. QUESTION

  6. A) B) and C) If the tin electrode were the cathode, the would be negative and thus nonspontaneous. ANSWER E cell

  7. Dry Cell Battery

  8. Chemistry of Batteries Dry Cells Anode (oxidation): Zn(s) Zn2+(aq) + 2 e- Cathode (reduction): 2 MnO2 (s) + 2 NH4+(aq) + 2 e- Mn2O3 (aq) + 2 NH3 (aq) + H2O(l) ammonia is tied up with Zn2+ Zn2+(aq) + 2 NH3 (aq) + 2 Cl-(aq) Zn(NH3)2Cl2 (s) Overall (cell) reaction: 2 MnO2 (s) + 2NH4Cl(aq) + Zn(s) Zn(NH3)2Cl2 (s) + H2O(l) +Mn2O3 (s)

  9. QUESTION What is the standard cell potential for a dry cell battery? Anode (oxidation): Zn(s) Zn2+(aq) + 2 e- Cathode (reduction): 2 MnO2 (s) + 2 NH4+(aq) + 2 e- Mn2O3 (aq) + H2O(l) Eo = 0.74V A) +0.74V B) -0.02V C) +1.50V D) +0.76V

  10. Answer What is the standard cell potential for a dry cell battery? Anode (oxidation): Zn(s) Zn2+(aq) + 2 e- Cathode (reduction): 2 MnO2 (s) + 2 NH4+(aq) + 2 e- Mn2O3 (aq) + H2O(l) Eo = 0.74V A) +0.74V B) -0.02V C) +1.50V D) +0.76V Zn2+(aq) + 2 e- Zn(s) Eo = -0.76V

  11. Current: C/s A= ampere (amp) mAh = Milliamp hour

  12. QUESTION Which statement is true? Since the voltages for AA, AAA, C, and D alkaline batteries are the same, it does not matter what device they are used in. A battery’s voltage depends on the amount of material in the voltaic cell. The leaking material often found on the outside of old alkaline batteries is a neutral pH salt. The current produced by a AAA alkaline battery would be higher than a AA battery. Primary batteries such as alkaline batteries cannot be recharged.

  13. ANSWER Which statement is true? Since the voltages for AA, AAA, C, and D alkaline batteries are the same, it does not matter what device they are used in. A battery’s voltage depends on the amount of material in the voltaic cell. The leaking material often found on the outside of old alkaline batteries is a neutral pH salt. The current produced by a AAA alkaline battery would be higher than a AA battery. Primary batteries such as alkaline batteries cannot be recharged.

  14. Chemistry of Batteries Alkaline Battery Anode (oxidation): Zn(s) + 2 OH-(aq) ZnO(s) + H2O(l) + 2 e - Cathode (reduction): MnO2 (s) + 2 H2O(l) + 2 e - Mn(OH)2 (s) + 2 OH -(aq) Overall (cell) reaction: Zn(s) + MnO2 (s) + H2O(l) ZnO(s) + Mn(OH)2 (s)Ecell = 1.5 V Leaking battery.

  15. Chemistry of Batteries Mercury and Silver (Button) Batteries Anode (oxidation): Zn(s) + 2 OH-(aq) ZnO(s) + H2O(l) Cathode (reduction) (mercury): HgO(s) + H2O(l) + 2 e- Hg(l) + 2 OH-(aq) Cathode (reduction) (silver): Ag2O(s) + H2O(l) + 2 e- 2 Ag(s) + 2 OH-(aq) Overall (cell) reaction (mercury): Zn(s) + HgO(s) ZnO(s) + Hg(l); Ecell = 1.3 V Overall (cell) reaction (silver): Zn(s) + Ag2O(s) ZnO(s) + 2 Ag(s); Ecell = 1.6 V

  16. Rechargeable Batteries Lead-Acid Batteries Anode (oxidation): Pb(s) + SO42-(aq) PbSO4 (s) + 2 e- Cathode (reduction): PbO2 (s) + 4 H+(aq) + SO42-(aq) + 2 e- PbSO4 (s) + 2 H2O(l) Overall (cell) reaction (discharge): PbO2 (s) + Pb(s) + 2 H2SO4 (aq) 2 PbSO4 (s) + 2 H2O(l); Ecell = 2 V Overall cell) reaction (recharge): 2 PbSO4 (s) + 2 H2O(l) PbO2 (s) + Pb(s) + 2 H2SO4 (aq)

  17. Automotive Application: the Discharge and Recharging of a Lead-Acid Battery

  18. Nickel-Cadmium (Nicad) Battery Used in photovoltaic low voltage lighting Anode (oxidation): Cd(s) + 2 OH-(aq) Cd(OH)2 (s) + 2 e- Cathode (reduction): 2 NiO(OH)(s) + 2 H2O(l) + 2 e- 2 Ni(OH)2 (s) + 2 OH-(aq) Overall (cell) reaction: Cd(s) + 2 NiO(OH)(s) + 2 H2O(l) 2 Ni(OH)2 (s) + Cd(OH)2 (s) Ecell = 1.4 V

  19. Solid Lithium Battery Anode (oxidation): Li(s) Li+ (s) + e- Cathode (reduction): MnO2 (s) + Li+ + e- LiMnO2 (s) Overall (cell) reaction: Li(s) + MnO2 (s) LiMnO2 (s); Ecell = 3 V

  20. Lithium Ion Battery Most Common Rechargeable Cell Phone Battery Anode (oxidation): Cathode (reduction): Ecell = 3.6 V

  21. 8:54 http://www.pbs.org/newshour/bb/world/july-dec11/syria_08-09.html

  22. QUESTION http://www.pbs.org/newshour/bb/world/july-dec11/syria_08-09.html “It's actually simple way to recharge your phone. We used to -- a glass of water with two batteries Duracell or something else. This already exists everywhere. We use it, keep the batteries in the water for one hour or 30 minutes. Then you put the USB adapters inside the water and start charge. That's how we charge the mobiles.“  Organize into three or four per group. Discuss Omar’s claim and determine what are the important criteria in answering A) or B). Pick a spokesperson for the group. A) This is nonsense. B) This is plausible.

  23. Lithium Ion Battery Rechargeable Car Battery Nissan Leaf

  24. Lithium Ion Batteries

  25. Chemistry of Batteries Flow Batteries (Fuel Cells) The Hydrogen Oxygen Fuel Cell Anode (oxidation): H2 (g) + CO32-(l) H2O(g) + CO2 (g) + 2 e- Cathode (reduction): 1/2 O2 (g) + CO2 (g) + 2 e- CO32-(l) Overall (cell) reaction: H2 (g) + 1/2 O2 (g) H2O(g)Ecell = 1.2 V

  26. Hydrogen Fuel Cell

  27. Chemistry of Batteries 2 NH3 (g) + 3/2 O2 (g) N2 (g) + 3 H2O(l) N2H4 (g) + O2 (g) N2 (g) + 2 H2O (l) CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O(l) Flow Batteries (Fuel Cells) Where doses the H2(g) come from? The Hydrogen Oxygen Fuel Cell Anode (oxidation): H2 (g) + CO32-(l) H2O(g) + CO2 (g) + 2 e- Cathode (reduction): 1/2 O2 (g) + CO2 (g) + 2 e- CO32-(l) Overall (cell) reaction: H2 (g) + 1/2 O2 (g) H2O(g)Ecell = 1.2 V Other Fuel Cells:

  28. QUESTION A fuel cell differs from typical batteries in what key aspect? The components in fuel cells are replenished without recharging. Fuel cells typically have a higher E° value than typical batteries. Fuel cells rely on solar power to thermochemically generate electrons. Although typical batteries may be made from a variety of components, fuel cells may only use H2 and O2.

  29. ANSWER Acontrasts fuel cells with other typical batteries. Typical batteries have the oxidizing and reducing agents packaged within the cell. The oxidizing and reducing agents for fuel cells, typically, are supplied continuously from sources external to the cell.

  30. Photovoltaic Electrolysis Which is O2(g) and which is H2(g)?

  31. http://www.youtube.com/watch?v=9hb7VNMzySg&feature=related http://www.youtube.com/watch?v=-oWvckf7D70&feature=related

  32. QUESTION

  33. C) The alkaline dry cell battery can last longer than a nickel cadmium battery. The basicity of the alkaline dry cell battery prevents the corrosion of the Zn electrode giving long life. ANSWER -

  34. Diagram of a TPV Generator Thermophotovoltaic: Conversion from heat to electricity via photons.

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