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Cells and Voltage

Cells and Voltage. Explain the operation of a voltaic ( galvanic ) cell at the visual, particulate and symbolic level Include: writing half-cell reactions and overall reaction. Additional KEY Terms line notation anode cathode salt bridge. Volta (1745-1827).

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Cells and Voltage

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  1. Cells and Voltage

  2. Explain the operation of a voltaic (galvanic) cell at the visual, particulate and symbolic level • Include: writing half-cell reactions and overall reaction Additional KEY Terms line notation anode cathode salt bridge

  3. Volta (1745-1827) • Electricalcurrentmade with spontaneousredox • Half-cellsareseparated from each other • Transfer of electronsforced through wire • Loadcan be runwith high enough voltage Voltaic cells (also called Galvanic cells) use a spontaneous redox reaction to convertchemical energy into electrical energy

  4. Electric current(I) –a flow of electrons. • e- move through conductors • redox e- transferredbetween metal electrodes • Voltage(V) – measure of e- ability to do work • also called electrical potential (E°)

  5. The following applies to ALL electrochemical cells A o node – electrode where xidation occurs • e-producedat anode • negative electrode C r athode – where eduction occurs • e-consumedat cathode • positive electrode

  6. 2 Ag+(aq) + Cu(s) → 2 Ag(s) + Cu2+(aq) Electrons will be transferred from copper to silver

  7. Anode loses mass: • e-aredonated by metal • ions dissolve in solution – (s) into (aq) • Eventually, anode is completely oxidized to ions electronsmove from anode to cathode("A to C") • Anode loses mass: • e-aredonated by metal • ions dissolve in solution – (s) into (aq) • anode slowly “used up” • Cathode gains in mass: • e-areacceptedby cations • cations are reduced – (aq) into (s) • “Plate out” onto the cathode

  8. You will have to completely label a diagram like this one

  9. Salt bridge - maintains charge balance • filled with an electrolyte solution (salt or acid) • allows movement of ions, withoutmixing cells • neutralizes half-cell products Ions build-up in both half-cells as the cell operates – if a cell solution gets too + or – electrons will stop moving through

  10. The excess positive and negative ions in the solution are neutralized by the salt bridge ions allowing the redox reaction to continue

  11. Line notation • a short hand notation of a voltaic cell. 2Ag+(aq)+Cu(s)→ 2 Ag(s)+Cu2+(aq)

  12. An electrochemical cell with Cu (II) oxidizing Zn is constructed. • Identify the anode and cathode. • Write the net equation for the reaction. • What direction do the electrons move? • What is the line notation?

  13. 1. Copper is the cathode – reduction. Zinc is the anode – oxidation. 2. Oxidation: Zn(s) → Zn2+(aq) + 2 e– Reduction: Cu2+(aq) + 2 e– → Cu(s) Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) 3. e- move from zinc half-cell to copper half-cell. 4. Zn(s) / Zn2+(aq) // Cu2+(aq) / Cu(s)

  14. CAN YOU / HAVE YOU? • Explain the operation of a voltaic (galvanic) cell at the visual, particulate and symbolic level • Include: writing half-cell reactions and overall reaction Additional KEY Terms line notation anode cathode salt bridge

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