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Unformatted text preview: 1 ELECTROCHEMISTRY ELECTROCHEMISTRY Chapter 21 Chapter 21 TRANSFER REACTIONS TRANSFER REACTIONS 2 Atom/Group transfer HCl + H 2O ---> HCl ---> ClCl + 3 Electron Transfer Reactions Electron Transfer Reactions • Electron transfer reactions are oxidationElectron oxidation- H3O+ reduction or redox reactions. redox • Redox reactions can result in the Electron transfer generation of an electric current or be Cu(s) + 2 Ag+(aq ) ---> Cu2+(aq) + 2 Ag(s) caused by imposing an electric current. • Therefore, this field of chemistry is often Electric automobile called ELECTROCHEMISTRY. called ELECTROCHEMISTRY. 4 5 6 Review of Terminology Review of Terminology for Redox Reactions for Redox Reactions OXIDATION-REDUCTION REACTIONS OXIDATION-REDUCTION OXIDATION-REDUCTION REACTIONS REACTIONS •• OXIDATION —loss of electron(s) by a OXIDATION—loss of electron(s) by a species; increase in oxidation number. species; increase in oxidation number. •• REDUCTION—gain of electron(s); REDUCTION—gain of electron(s); decrease in oxidation number. decrease in oxidation number. Direct Redox Reaction Oxidizing and reducing agents in direct contact. Cu(s) + 2 Ag+(aq ) ---> Cu2+(aq) + 2 Ag(s) Indirect Redox Reaction •• OXIDIZING AGENT —electron acceptor; OXIDIZING AGENT—electron acceptor; species is reduced. species is reduced. •• REDUCING AGENT—electron donor; REDUCING AGENT—electron donor; species is oxidized. species is oxidized. Page 1 A battery functions by transferring electrons through an external wire from the reducing agent to the oxidizing agent. Why Study Electrochemistry? Why Study Electrochemistry? • Batteries • Corrosion • Industrial production of chemicals such as such Cl2, NaOH, F2 and Al • Biological redox reactions 7 8 Electrochemical Cells Electrochemical Cells • An apparatus that allows a redox reaction to occur by transferring electrons through an external connector. • Product favored reaction ---> voltaic or galvanic cell ----> electric current • Reactant favored reaction ---> electrolytic cell ---> electric current used to cause chemical change. The heme group Page 2 Batteries are voltaic cells ...
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