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Electrochemistry

Learn about galvanic cells, anodes, cathodes, standard electrode potentials, and electrical potential differences in electrochemistry. Explore how oxidation and reduction reactions occur to generate current in batteries.

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Electrochemistry

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  1. Electrochemistry

  2. Electrochemistry • To obtain a useful current, we separate the oxidation and reduction half-reactions so that electron transfer occurs thru an external wire. This is accomplished in a GALVANIC or VOLTAIC cell. A group of such cells is called a battery. http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/galvan5.swf

  3. Galvanic Cells Anode= oxidation Cathode= reduction - + spontaneous redox reaction 19.2

  4. E0 = Ecathode - Eanode cell Standard emf (E0 ) cell 0 0 GalvanicCells • The difference in electrical potential between the anode and cathode is called: • cell voltage • electromotive force (emf) • cell potential 19.2

  5. Standard Electrode Potentials Standard reduction potential (E0) is the voltage associated with a reduction reaction at an electrode when all solutes are 1 M and all gases are at 1 atm. • E0 is for the reaction as written • The more positive E0 the greater the tendency for the substance to be reduced • In a cell, the substance with the greater E0 value is at the cathode (where reduction takes place) 19.3

  6. Cd2+(aq) + 2e- Cd (s)E0 = -0.40 V Cr3+(aq) + 3e- Cr (s)E0 = -0.74 V E0 = -0.40 - (-0.74) E0 = 0.34 V E0 = Ecathode - Eanode cell cell cell 0 0 What is the standard emf of an electrochemical cell made of a Cd electrode in a 1.0 M Cd(NO3)2 solution and a Cr electrode in a 1.0 M Cr(NO3)3 solution? Cd2+ will be reduced (at the cathode) Cr(s) will be oxidized (at the anode) 19.3

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