Ch21_3 - 1 Basic Concepts of Electrochemical Cells CHEMICAL...

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Unformatted text preview: 1 Basic Concepts of Electrochemical Cells CHEMICAL CHANGE ---> CHEMICAL CHANGE ---> ELECTRIC CURRENT ELECTRIC CURRENT Zn metal Zn metal Cu2+ iions Cu2+ ons Anode Cathode Cu2+ ions This is accomplished in a GALVANIC or This GALVANIC VOLTAIC cell. A group of such cells is called a group 6 Electrons move from anode to cathode in the wire. Anions & cations move thru the salt bridge. Cu salt bridge Cu salt bridge Zn2+ ions 5 ele c t rons ele c t rons battery . battery Zn2+ ions Cu2+ ions •Electrons travel tthru external wire. •Electrons travel hru external wire. ••Salt bridge allows anions and cations tto Salt bridge allows anions and cations o Salt allows move between electrode compartments. move between electrode compartments. ••This maintains electrical neutrality. This maintains electrical neutrality. Page 1 Electrons are Electrons are transferred from Zn to transferred from Zn to Cu2+,, but there is no Cu2+ but there is no useful electric current. useful electric current. Oxidation: Zn(s) ---> Zn 2+(aq) + 2eReduction: Cu2+(aq) + 2e- ---> Cu(s) -------------------------------------------------------Cu2+(aq) + Zn(s) ---> Zn 2+(aq) + Cu(s) wire Zn 3 Zn metal Zn metal Cu2+ iions Cu2+ ons 4 wire Zn CHEMICAL CHANGE ---> CHEMICAL CHANGE ---> ELECTRIC CURRENT ELECTRIC CURRENT With time, Cu plates out With time, Cu plates out onto Zn metal strip, and onto Zn metal strip, and Zn strip “disappears.” Zn strip “disappears.” •Zn is oxidized and is the reducing agent and Zn(s) ---> Zn2+(aq) + 2e2+ is reduced and is the oxidizing agent •Cu and Cu2+(aq) + 2e- ---> Cu(s) CHEMICAL CHANGE ---> CHEMICAL CHANGE ---> ELECTRIC CURRENT ELECTRIC CURRENT •To obtain a useful current, we separate the oxidizing and reducing agents so that electron transfer occurs thru an external wire. 2 Electrochemical Electrochemical Cell Cell 7 Anode, site of oxidation, negative Cathode, site of reduction, positive Page 2 ...
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This note was uploaded on 10/19/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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