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Chp 17 Electrochemistry

Chp 17 Electrochemistry. Galvanic Cells. A device in which chemical energy is converted into electrical energy Oxidation – reduction (redox) reactions e- ‘s transfer from reducing agent to oxidizing agent. Galvanic Cell. Voltage meter. e -. e -. e -. Salt Bridge Why?. Zn. Cu. Zn 2+

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Chp 17 Electrochemistry

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  1. Chp 17 Electrochemistry

  2. Galvanic Cells • A device in which chemical energy is converted into electrical energy Oxidation – reduction (redox) reactions e- ‘s transfer from reducing agent to oxidizing agent

  3. Galvanic Cell Voltage meter e- e- e- Salt Bridge Why? Zn Cu Zn 2+ SO4 2- Cu 2+ SO42- http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/galvan5.swf

  4. What is happening to the Zn and the Cu? Zn is making electrons (oxidization) Cu is gaining electrons (reduction) Anode where electrons are produced. Cathode where electrons are used. Cell potential cell (volt) or (V) Zn disappearing Forming Cu

  5. Standard Reduction Potentials Anode: Zn(s)  Zn 2+(aq) + 2 e- Cathode: Cu 2+(aq) + 2 e-  Cu (s) ocell = ocat + oan ocell = (+0.76V) + (+0.34V) = +1.10 V Must be positive

  6. Examples Fe 3+(aq) + Cu (s)  Cu 2+(aq) + Fe 2+(aq) Half reactions Red: ( Fe 3+ + 1e -  Fe 2+) Ox: Cu  Cu 2+ + 2e – 2Fe 3+(aq) + Cu (s)  Cu 2+(aq) + 2Fe 2+(aq) ocell = ocat + oan ocell = 0.43 V o = 0.77 V 2 o = - 0.34 V Opposite sign because of Ox = 0.77 V + (-0.34 V)

  7. Line Notation Zn (s) + Cu 2+(aq)  Zn 2+(aq) + Cu (s) Zn(s) l Zn 2+(aq) ll Cu 2+(aq) l Cu(s) electrode electrode

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