Zumdahl+Chapter+9+lecture+notes

# Zumdahl+Chapter+9+lecture+notes - Chapter 9 Energy,...

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11/20/07 Zumdahl Chapter 9 1 Chapter 9 Energy, Enthalpy, and Thermochemistry 9.1 The Nature of Energy 9.2 Enthalpy 9.3 Thermodynamics of Ideal Gases 9.4 Calorimetry 9.5 Hess's Law 9.6 Standard Enthalpies of Formation 9.7 Present Sources of Energy (skip) 9.8 New Energy Sources (skip)

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2 The Person Behind the Science James Prescott Joule (1818-1889) Highlights Studied the nature of heat, and discovered its relationship to mechanical work Led to the theory of conservation of energy, which led to the development of the first law of thermodynamics Worked with Lord Kelvin to develop the absolute scale of temperature Pupil of John Dalton (Atomic Theory) Joule effect: found the relationship between the flow of current through a resistance and the heat dissipated, now called Joule's law Moments in a Life Gravestone is inscribed with the number “772.55” the amount of work, in ft lb, he determined experimentally to be required to raise the temperature of 1 lb of water by 1° Fahrenheit. “772.55”
11/20/07 Zumdahl Chapter 9 3 Reactants ! Products

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11/20/07 Zumdahl Chapter 9 4 Thermite Reaction 2 Al (s) + Fe 2 O 3 (s) ! Al 2 O 3 (s) + 2Fe (s) Reactants ! Products
11/20/07 Zumdahl Chapter 9 5 The Nature of Energy Law of conservation of energy : energy can be converted from one form to another but can be neither created of destroyed. • Potential energy ( e.g ., ! E potential = mg ! h) • Kinetic energy ( e.g ., ! E Kinetic = ! (1/2 mv 2 ) • Energy transfer – Through heat (frictional heating) – Through work • The study of energy and its interconversions is called thermodynamics

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11/20/07 Zumdahl Chapter 9 6 First Law of Thermodynamics “The Law of Conservation of Energy” ! E = q + w where E is the internal energy of a system) q = Heat Absorbed by a system ! If q > 0 , heat is absorbed ! If q < 0 , heat is given off w is the work done on or by the system Recall " w = F x d " w = ! E Kinetic = ! ( " mv 2 ) " w = ! E potential = mg ! h In chemistry this kind of mechanical work is Pressure-Volume work (P-V)
11/20/07 Zumdahl Chapter 9 7 Exo thermic reactions release energy CH 4 ( g ) + 2O 2 ( g ) # CO 2 ( g ) +2 H 2 O ( g ) + Energy (heat) In an exo thermic reaction, the potential energy stored in the chemical bonds is being converted to thermal energy (random kinetic energy) via heat

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11/20/07 Zumdahl Chapter 9 8 Endo thermic reactions release energy N 2 ( g ) + O 2 ( g ) + Energy (heat) # 2 NO ( g ) An endo thermic reaction consumes heat and stores heat in the chemical bonds of the products.
11/20/07 Zumdahl Chapter 9 9 Thermodynamic Internal Energy Flow Note the number and the sign

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11/20/07 Zumdahl Chapter 9 10 Thermodynamic Work w = F x d = F x ! h = P x A x ! h ! V = A ! h
11/20/07 Zumdahl Chapter 9 11 • Force exerted by heating = P 1 A – Where P 1 is the pressure inside the vessel – Where A is the Area of the piston P ext = P 1 if balanced w = F x d = F x ! h = P x A x ! h ! V = A ! h w = " P ext ! V – Units are atm·L or L atm Where 1 L atm = 101.3 Joules ratio of Gas law constants 8.3145 J 101.3J K mol = = 0.08206L atm L atm K mol

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11/20/07 Zumdahl Chapter 9 12 • Expansion – The system does work on the surroundings • Compression
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## This note was uploaded on 08/28/2011 for the course CHEM 1310 taught by Professor Cox during the Spring '08 term at Georgia Institute of Technology.

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Zumdahl+Chapter+9+lecture+notes - Chapter 9 Energy,...

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