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Chapter 20
Spontaneous Change: Entropy and Free Energy
 
 
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 The exothermic reaction between Fe2O3 and aluminum is demonstrated.
Notes
 In the thermite reaction, Al reduces Fe2O3 to Fe in an extremely exothermic reaction in which Al is oxidized to Al2O3. The reaction produces enough heat to melt the iron. Because of the extreme heat produced in the thermite reaction, it is used industrially to weld iron.
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 Animation illustrating Boyle's law
Notes
 As the pressure of a gas is increased at constant temperature its volume decreases in a nonlinear fashion. A plot of volume as a function of 1/P is linear. This is consistent with Boyle's law which states that the pressure and volume of a gas are inversely proportional.
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 Changes of State
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 As a solid is heated its temperature increases until its melting point is reached. At the melting point heat is used to convert the solid to a liquid at constant temperature. In the liquid state the temperatureincreases with added heat. At the boiling point the heat is used to convert the liquid to vapor at constant temperature. When the substance has vaporized, added heat causes the temperature of the vapor to increase.
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 The effect of temperature on the vapor pressure of a liquid is illustrated.
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 A liquid in a closed container exerts a vapor pressure due to molecules that have escaped into the liquid phase. At equilibrium equal numbers of molecules leave and reenter the liquid phase. As the temperature is increased the average kinetic energy of the molecules increases. The higher kinetic energy of the liquid allows more molecules to escape, resulting in an increase in vapor pressure with increasing temperature.
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 Temperature dependent equilibrium between NO2 and N2O4
Notes
 In a closed container the reddish-brown gas NO2 is in equilibrium with the colorless gas N2O4. According to Le Chatelier's principle when the temperature of an equilibrium system is increased at constant volume the equilibrium shifts in the direction that absorbs heat. Since the conversion of 2NO2 to N2O4 is an exothermic reaction, the equilibrium shifts in favor of NO2 when the temperature is increased from 373 K to 473 K.
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 Effect of pressure on the equilibrium between NO2 and N2O4
Notes
 The reddish-brown gas NO2 exists in equilibrium with the colorless gas N2O4. If the volume of an equilibrium mixture of the two gases is halved, the pressures of both of the gases double and the system is no longer at equilibrium. According to Le Chatelier's principle the equilibrium will shift to decrease the pressure, i.e. there will be a net conversion of NO2 to N2O4 resulting in a decrease in the total number of molecules.
20.0.1UN
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 P 783-1
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 A toy monkey doll with cymbals
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 A toy monkey doll with cymbals
20.0.2UN
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 P 783-1a
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 A melting ice cube forms a small pool of water on a bright blue surface
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 A melting ice cube forms a small pool of water on a bright blue surface
20.1a,b
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 20-1
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 glass bulbs joined by a stopcock with all gas in left bulb (initial condition)
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 glass bulbs joined by a stopcock with all gas in left bulb (initial condition)
20.2
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 20-2
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 The mixing of ideal gases.
20.2.1UN
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 p 785-1a
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 A bust of Austrian physicist Ludwig Boltzmann marks his tomb
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 A bust of Austrian physicist Ludwig Boltzmann marks his tomb
20.3a
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 20-3
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 Energy levels for a particle in boxes of lengths L, 2L, and 3L
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 Energy levels for a particle in boxes of lengths L, 2L, and 3L
20.4
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 Pressure_volume work conducted nearly reversibly.
20.5
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Notes
 Entropy and disorder„three processes in which entropy increases.
20.6.1
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Notes
 An entropy-based rationale of RaoultÍs law.
20.7
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 Molar entropy as a function of temperature
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 Molar entropy as a function of temperature
20.8
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 Vibrational energy and entropy.
20.8.1UN-T
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 Ball and stick model of methane
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 Ball and stick model of methane
20.8.2UN
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 p 794-1
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Notes
 J. Willard Gibbs (1839_1903)
20.9
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 20-9
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 Free energy change as a function of temperature.
20.10
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 20-10
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 Liquid-vapor equilibrium and the direction of spontaneous change
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 Liquid-vapor equilibrium and the direction of spontaneous change
20.11
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 20-11
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 Free energy change, equilibrium, and the direction of spontaneous change
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 Free energy change, equilibrium, and the direction of spontaneous change
20.11.1UN
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 Table 20.2
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 Table 20.2
20.11.2UN
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 p 805
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 Boise Cascade paper plant emits clouds of smoke into the air in Rumford, ME
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 Boise Cascade paper plant emits clouds of smoke into the air in Rumford, ME
20.12
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Notes
 Temperature dependence of the equilibrium constant Kp for the reaction
20.12.1UN
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 p 812
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 Mitochondria in endoplasmic reticulum of a pancreatic acinar cell
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 Mitochondria in endoplasmic reticulum of a pancreatic acinar cell
20.13
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 20-13
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 Coupled Reactions
Notes
 Coupled Reactions
20.13.2UN
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 p 821-1
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Notes
 DG_ for three reactions as a function of temperature
20-efx
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 20-efx
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 Effects of raising the temperature of a substance on the entropy of the system
p 791-1a
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 Zooms for an entropy-based rationale of Raoult's law
p 793-1
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Notes
 Ball and stick model of propane
p 793-1a
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Notes
 Ball and stick model of ethane
p 812-1a
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Notes
 adenosine, adp, and atp
Table 20.1
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 Table 20.1
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Notes
 criteria for spontaneous change: Del G=