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Electrochemistry

Electrochemistry. Voltaic Cells. Voltaic (Galvanic) Cells - spontaneous reaction used to produce electrical energy. Salt Bridge Cells Zn(s) + Cu 2+ (aq) → Zn 2+ (aq) + Cu(s). video.

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Electrochemistry

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  1. Electrochemistry Voltaic Cells

  2. Voltaic (Galvanic) Cells - spontaneous reaction used to produce electrical energy. Salt Bridge Cells Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) video

  3. The salt bridge allows the current to flow but prevents contact between Zn and Cu2+, which would short-circuit the cell. salt bridge demo

  4. For the reaction: Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g) use an inert Pt electrode for H+/H2 half-cell. Bubble in H2 over the Pt electrode. video

  5. Standard Voltages Eo = cell voltage when all species are at standard concentrations (1 atm for gases, 1M for solutions). Zn + 2 H+ → Zn2+ + H2 Eo= + 0.762 V = Eox (Zn) + Ered (H+) Ered of H+ is arbitrarily set to zero. Appendix E on page 1117 is a list of standard reduction potentials. The oxidation potential is obtained by changing the sign.

  6. Ex Find the cell potential of the Zn - Cu cell.

  7. The more positive the value of Ered, the more easily reduced and the stronger the oxidizing agent. • The more negative the value of Ered, the more easily oxidized and the stronger the reducing agent. animation

  8. Calculation of Eo. Eo= Eox + Ered Cl2(g) + 2 Br-(aq) → 2 Cl-(aq) + Br2(l) Eo= Ered + Eox = ECl2 + EBr- = 1.360 V - 1.077 V = +0.283 V Since the calculated voltage is positive, this voltage can occur in a voltaic cell and the cell will produce electricity.

  9. Ex - What, if anything, will happen when bromine is added to a solution of tin(II) chloride? If Br2 is reduced, Sn2+ cannot be Will give a negative E with Br2

  10. Notes Quiz https://docs.google.com/spreadsheet/embeddedform?formkey=dHFNTkFGU1pPUEpyZ0pqNnktWGVkYVE6MQ

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