Lecture10 - Electrochemistry Chemical Change and Electrical...

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1 Chapter 21 Electrochemistry: Chemical Change and Electrical Work Electrochemistry: Chemical Change and Electrical Work 21.1 Half-Reactions and Electrochemical Cells 21.2 Voltaic Cells: Using Spontaneous Reactions to Generate Electrical Energy 21.3 Cell Potential: Output of a Voltaic Cell 21.4 Free Energy and Electrical Work 21.5 Electrochemical Processes in Batteries 21.6 Corrosion: A Case of Environmental Electrochemistry 21.7 Electrolytic Cells: Using Electrical Energy to Drive a Nonspontaneous Reaction Basic Lessons/Concepts • Oxidation Numbers Æ electron book keeping • Identifying Redox reactions (cases where electron transfer occurs) Æ Changes in oxidation numbers • Electrochemistry = Redox chemistry at electrodes • The ability to separate chemical reagents and control reactions by virtue of electron conduction through wires = ability to store and control release of chemical potential energy (batteries) • Electrons flow in direction of spontaneous reaction (release stored chemical potential energy)…driving force Æ cell potential • Reduction potentials tabulated relative to a standard reference (hydrogen electrode) • Cell potentials are fundamentally related to the reaction free energy ( Δ G…spontaneity, max. work, equilibrium constants) Review of Previous Lecture 1. Electrochemical Cells Half (redox) reactions connected by virtue of wires….electrons free to move in direction of spontaneous reaction (half reaction with largest reduction potential) Ions in solution are mobile (move to compensate charge from electron transfer….complete the circuit) Æ salt bridge/physical separation but permits ion diffusion Electrons move to lower chemical potential….potential drop = cell voltage Determine reduction half reaction potentials relative to standard hydrogen electrode (SHE) reference Æ powerful tool for predicting whether a reaction will occur or not and maximum work that can be obtained from a reaction
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This note was uploaded on 04/18/2011 for the course CHM 151 taught by Professor Dong during the Winter '08 term at University of Toronto.

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Lecture10 - Electrochemistry Chemical Change and Electrical...

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