221-chapter-14

221-chapter-14 - Fundamentals of Electrochemistry...

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Fundamentals of Electrochemistry Introduction 1.) Electrical Measurements of Chemical Processes Redox Reaction involves transfer of electrons from one species to another. - Chemicals are separated Can monitor redox reaction when electrons flow through an electric current - Electric current is proportional to rate of reaction - Cell voltage is proportional to free-energy change Batteries produce a direct current by converting chemical energy to electrical energy. - Common applications run the gamut from cars to ipods to laptops
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Fundamentals of Electrochemistry Basic Concepts 1.) A Redox titration is an analytical technique based on the transfer of electrons between analyte and titrant Red uction-ox idation reaction A substance is reduced when it gains electrons from another substance - gain of e - net decrease in charge of species - Oxidizing agent (oxidant) A substance is oxidized when it loses electrons to another substance - loss of e - net increase in charge of species - Reducing agent (reductant) (Reduction) (Oxidation) Oxidizing Agent Reducing Agent
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Fundamentals of Electrochemistry Basic Concepts 2.) The first two reactions are known as “1/2 cell reactions” Include electrons in their equation 3.) The net reaction is known as the total cell reaction No free electrons in its equation 4.) In order for a redox reaction to occur, both reduction of one compound and oxidation of another must take place simultaneously Total number of electrons is constant ½ cell reactions : Net Reaction :
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Fundamentals of Electrochemistry Basic Concepts 5.) Electric Charge ( q ) Measured in coulombs (C) Charge of a single electron is 1.602x10 -19 C F n q = Relation between charge and moles: Coulombs moles - e mol Coulombs
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Fundamentals of Electrochemistry Basic Concepts 7.) Electric Potential ( E ) Measured in volts (V) Work (energy) needed when moving an electric charge from one point to another - Measure of force pushing on electrons q E work G - = - = Relation between free energy, work and voltage: Joules Volts Coulombs Higher potential difference Higher potential difference requires more work to lift water (electrons) to higher trough
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Fundamentals of Electrochemistry Basic Concepts 7.) Electric Potential ( E ) Combining definition of electrical charge and potential q E work G - = - = F n q = nFE G - = Relation between free energy difference and electric potential difference: Describes the voltage that can be generated by a chemical reaction
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221-chapter-14 - Fundamentals of Electrochemistry...

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