Lecture1510fb

Lecture1510fb - Chemistry 83" 10/26/10 " Natural...

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•Chemistry 83 •10/26/10 • 1 Natural Limitations on Chemical Technologies Nature of chemical technologies Limitations on chemical technologies Making decisions about technologies Report 3 Nature of a Chemical Technology
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•Chemistry 83 •10/26/10 • 2 Outer Space Solar Energy Heat Earth’s Environment Extraction Reactants Recycled Materials reaction Materials to provide man's needs and wants + Used Materials Waste Materials (By-products) Heat (Degraded- energy) Chemical + Waste Components of Typical Chemical Technology Any technology that carries out a chemical reaction that converts resource(s) into a product that is sold (with or without further modiFcation) to consumers is a chemical technology ( 20% GDP) Matter and Energy Limitations on Chemical Technologies Minimizing limitations
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•Chemistry 83 •10/26/10 • 3 There are natural limitations on energy transformations in chemical technologies • The maximum work that a given amount of energy can do is given by the Frst law of energy (Conservation of Energy) • The actual work that a given amount of energy can do is limited by the second law of energy (nature ʼ s heat tax) • Quantified by %-efficiency, which = 100(Useful work output)/(Energy Input) Hinrichs, Energy, 2nd, Saunders, NY,1996, 78-79
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•Chemistry 83 •10/26/10 • 4 (98.4% of original chemical energy of coal is degraded to heat and dispersed!) Hinrichs, Energy, 2nd, Saunders, NY,1996, 85 The total efFciency of a process that involves several energy conversions is the product of the efFciencies for the conversions Minimize number of conversions to maxmimize overall energy efFciency There are natural limitations on matter transformations in chemical technologies • The maximum mass of product that can be obtained from a given reaction is limited by the Law of Conservation of Mass (calculated from coefFcients of balanced chemical equation) • The actual mass of product that can be obtained from a given reaction is limited by competing reactions such as: C + O 2 CO and CO 2 • Quantified by %-yield, which = 100(Actual yield)/(calculated yield)
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•Chemistry 83 •10/26/10 • 5 • Reversible reaction involves two reactions with one being the reverse of the other • Reversible reactions are represented by one equation using a double arrow: One common type of competing chemical reaction is called a reversible reaction N 2 O 4 2 NO 2 Forward Reverse McMurray/Fay, Chemistry,Prentice Hall, NJ, 1995, 498
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This note was uploaded on 12/19/2010 for the course CHEM 83 taught by Professor Bonk,j during the Fall '08 term at Duke.

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Lecture1510fb - Chemistry 83" 10/26/10 " Natural...

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