Chem 30-1 14.2 Notes - 14.2 Voltaic Cells Electrons pass...

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14.2 Voltaic CellsElectrons pass from the reducing agent to the oxidizing agent through an external circuit rather than passing directly from one substance to anotherElectrodes and electrolytes determine characteristics such as voltage and currentPorous Boundary:a physical barrier separating two electrolytes while still permitting ions to move between the two solutions through tiny openingsHalf-Cell:an electrode-electrolyte combination forming one-half of a complete celloEg: A copper-zinc cell has two half-cells, copper metal in a solution of copper ions and zinc metal in a solution of zinc ionsoThis can be represented in an abbreviated (“shorthand”) notation, called a cell notation:oSEE PAGE 622A single line (|):indicates a phase boundary, such as the interface of an electrode and an electrolyte in a half-cellA double line (||):represents a physical boundary, such as a porous boundary between half-cellsWrite the cell notation with the anode on the left-hand side and the cathode on the right-hand sideVoltaic Cell:an arrangement of two half-cells, separated by a porous boundary, that spontaneously produces electricityA Theoretical Description of a Voltaic CellThe strongest oxidizing agents undergo a reduction half-reaction at the cathodeThe strongest reducing agent in the cell always undergoes an oxidation at the anodeSOAC/GERC (Soak a Jerk): Strongest Oxidizing Agent at the Cathode Gains Electrons and is Reduced“An Ox Ate a Red Cat”: Anode Oxidation; Reduction CathodeEg: To write the net equation for a silver-copper voltaic cell, identify the SOA/SRA. Then follow the same procedure for predicting half-reactions in which the two materials are in contact with each otherTAKE PIC OF REDUCTION OXIDATION THING AT CATHODE ANODE PAGE 624For a general voltaic cell
anode (-) | electrolyte || electrolyte | cathode (+)Voltaic Cells with Inert ElectrodesCells containing metals and metal ions, the electrodes are usually the metals, and half-reactions take place on the surface of the metalsIf one is not able to use a certain electrode because it will either dissolve in the electrolyte, or because it will not conduct electricity, then one may use an inert electrodeInert Electrode:provides a location to connect a wire and a surface on which a half-reaction can occur; a solid conductor that will not react in the cell or interfere with the desired cell reaction; carbon and platinum are common inert electrodesElectric Cell:Consumer cellsVoltaic Cell:Scientific research cellsElectrochemical Cell:includes both voltaic (spontaneous) and electrolytic (nonspontaneous) cellsSummary: Voltaic CellsA voltaic cell consists of two half-cells separated by a porous boundary with solid electrodes connected by an external circuitThe cathode is the positive electrode. The SOA is reduced at the cathodeThe anode is the negative electrode. The SRA is oxidized at the anode

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