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Key Concepts PowerPoint

Chapter 8
Thermochemistry: Chemical Energy

  
08-01
Title
 Conservation of Energy
Caption
 Figure 8.1 Conservation of energy. The total amount of energy contained by the water in a reservoir is constant. (a) At the top of the dam, the energy is potential (EP). (b)-(c) As the water falls over the dam, its velocity increases, and potential energy is converted into kinetic energy (EK). (d) At the bottom of the dam, the kinetic energy gained by the water is largely converted into heat and sound as the water dashes against the rocks.
Notes
 Potential energy and kinetic energy
Keywords
 potential energy, kinetic energy
08-02
Title
 System and Surroundings
Caption
 Figure 8.2 When energy changes are measured in a chemical reaction, the system is the reaction mixture being studied, and the surroundings are the flask, the room, and the rest of the universe. The energy change is the difference between final and initial states (DE = Efinal -Einitial). Any energy that flows from the system to the surroundings has a negative sign because Efinal is smaller than Einitial, and any energy that flows into the system from the surroundings has a positive sign because Efinal is larger than Einitial.
Notes
 Flow of energy between system and surroundings
Keywords
 energy, system, surroundings
08-04
Title
 Expansion Work
Caption
 Figure 8.4 The expansion in volume that occurs during a reaction forces the piston outward against atmospheric pressure P. The amount of work done is equal to the pressure exerted in moving the piston (the opposite of atmospheric pressure, -P) times the volume change (DV). The volume change is equal to the area of the piston (A) times the distance the piston moves (d). Thus, w = -PDV.
Notes
 Work done during expansion
Keywords
 work, expansion, pressure
08-04-03UN
Title
 Key Concept Problem 8.4
Caption
 How much work is done (in kilojoules), and in which direction, as a result of the following reaction?
Notes
 Key concept problem 8.4
Keywords
 key concept, work
08-04-06UN
Title
 Key Concept Problem 8.5
Caption
 Work and enthalpy.
Notes
 Key concept problem 8.5
Keywords
 key concept, work, enthalpy
08-04-07UN
Title
 Trinitrotoluene
Caption
 Ball-and-stick structure of trinitrotoluene (TNT).
Notes
 For problem 8.7
Keywords
 trinitrotoluene, TNT, work
08-05
Title
 Enthalpy as a State Function
Caption
 Figure 8.5 Because enthalpy is a state function, the enthalpy change from solid to vapor does not depend on the path taken between the two states. Therefore, DHsubl = DHfusion +DHvap.
Notes
 Enthalpy of sublimation, fusion, and vaporization
Keywords
 ethalpy, state function, sublimation, fusion, vaporization
08-08
Title
 Diagram of a Calorimeter
Caption
 Figure 8.8 A calorimeter for measuring the heat flow in a reaction at constant pressure (DH). The reaction takes place inside an insulated vessel outfitted with a loose-fitting top, a thermometer, and a stirrer. Measuring the temperature change that accompanies the reaction makes it possible to calculate DH.
Notes
 Calorimeter for measuring heat flow in a reaction
Keywords
 calorimeter, calorimetry
08-09
Title
 Bomb Calorimeter
Caption
 Figure 8.9 A bomb calorimeter for measuring the heat evolved at constant volume in a combustion reaction (DE). The reaction is carried out inside a steel bomb, and the heat evolved is transferred to the surrounding water, where the temperature rise is measured.
Notes
 Bomb calorimetry for measuring heat evolved from a combustion reaction
Keywords
 bomb calorimeter, calorimetry, combustion
08-10
Title
 Enthalpy of Formation of Ammonia
Caption
 Figure 8.10 A representation of the enthalpy changes for steps in the synthesis of ammonia from nitrogen and hydrogen. If DH° values for step 2 and for the overall reaction are known, then DH° for step 1 can be calculated. That is, the enthalpy change for the overall reaction is equal to the sum of the enthalpy changes for the individual steps 1 and 2, a statement known as Hess’s law.
Notes
 Enthalpy changes for steps in the synthesis of ammonia from nitrogen and hydrogen
Keywords
 Hess's law, enthalpy
08-10-01UN
Title
 Methylene chloride
Caption
 Ball-and-stick structure of methylene chloride.
Notes
 Problem 8.13
Keywords
 methylene chloride
08-10-02UN
Title
 Key Concept Problem 8.14
Caption
 Hess's law diagram.
Notes
 Key concept problem 8.14
Keywords
 key concept, Hess's law, enthalpy
08-11
Title
 Using Standard Heats of Formation
Caption
 Figure 8.11 The standard reaction enthalpy, DH°, for the generalized reaction A --> B is the difference between the standard heats of formation of products and reactants. Since the different heats of formation are referenced to the same point (the constituent elements), they are referenced to each other.
Notes
 Standard enthalpy of reaction is equal to the difference in the standard heats of formation for the reactants and the products.
Keywords
 reaction enthalpy, heat of formation
08-11-02UN
Title
 Ethyl alcohol
Caption
 Ball-and-stick structure of ethyl alcohol.
Notes
 Problem 8.18
Keywords
 ethyl alcohol
08-12
Title
 Products from Petroleum Refining
Caption
 Figure 8.12 The products of petroleum refining. The different fractions are grouped according to the number of carbon atoms their molecules contain.
Notes
 Products from petroleum refining
Keywords
 petroleum refining
08-12-01UN
Title
 Butane
Caption
 Ball-and-stick structure of butane.
Notes
 Problem 8.20
Keywords
 butane
08-13
Title
 Entropy and Phase Changes
Caption
 Figure 8.13 Entropy is a measure of molecular randomness, or disorder. Gases have more randomness and higher entropy than liquids, which in turn have more randomness and higher entropy than solids.
Notes
 Entropy as a measure of randomness, or disorder, in a system.
Keywords
 entropy, disorder
08-13-02UN
Title
 Key Concept Problem 8.22
Caption
 Is the reaction represented by the diagram likely to have a positive or negative change in entropy?
Notes
 Key concept problem 8.22
Keywords
 key concept, entropy
08-13-03UN
Title
 Gibbs free-energy change
Caption
 Equation for calculating the free-energy change determines whether a process is spontaneous or nonspontaneous at a given temperature; previously encountered thermodynamic terms, enthalpy and entropy, are involved in determining the free-energy change.
Notes
 Calculating Gibbs free-energy change for a process
Keywords
 Gibbs free-energy, free energy, spontaneity
08-15
Title
 Spontaneity of a Phase Change
Caption
 Figure 8.14 The melting of ice is disfavored by enthalpy (+DH) but favored by entropy (+DS). The freezing of water is favored by enthalpy (-DH) but disfavored by entropy (-DS). Below 0°C, the enthalpy term DH dominates the entropy term TDS in the Gibbs free-energy equation, so freezing is spontaneous. Above 0°C, the entropy term dominates the enthalpy term, so melting is spontaneous. At 0°C, the entropy and enthalpy terms are in balance.
Notes
 Is the melting of ice or freezing of ice a spontaneous process?
Keywords
 free-energy, spontaneity, phase change
08-15-01UN
Title
 Diagram for Key Concept Example 8.13
Caption
 What are the signs of each of the thermodynamic terms for the nonspontaneous process represented by the diagram?
Notes
 Key concept example 8.13
Keywords
 key concept, enthalpy, entropy, free-energy
08-15-02UN
Title
 Key Concept Problem 8.25
Caption
 Diagram represents an exothermic reaction; what are the signs of each of the thermodynamic terms for this system?
Notes
 Key concept problem 8.25
Keywords
 key concept, enthalpy, entropy, free-energy
08-15-030UN
Title
 Key Concept Summary
Caption
 Thermochemistry: chemical energy key concept summary.
Notes
 Key concept summary Chapter 8
Keywords
 key concept, summary
08-15-04UN
Title
 Diagram for Problem 8.26
Caption
 Work and enthalpy.
Notes
 Problem 8.26
Keywords
 key concept, work, enthalpy
08-15-06UN
Title
 Diagram for Problem 8.28
Caption
 Apply Hess's law to the reaction between acetylene and hydrogen gas.
Notes
 Key concept problem 8.28
Keywords
 key concept, Hess's law, enthalpy
08-15-08UN
Title
 Diagram for Problem 8.31
Caption
 Gibbs free-energy and spontaneity.
Notes
 Key concept problem 8.31
Keywords
 key concept, free-energy, spontaneity
08-15-09UN
Title
 Diagram for Problem 8.32
Caption
 What are the signs of the thermodynamic terms for the spontaneous process represented by the diagram?
Notes
 Key concept problem 8.32
Keywords
 key concept, enthalpy, entropy, free-energy
08-15-10UN
Title
 Diagram for Problem 8.33
Caption
 What are the signs of the thermodynamic terms for the spontaneous reaction represented by the diagram?
Notes
 Key concept problem 8.33
Keywords
 key concept, enthalpy, entropy, free-energy
08-TB01
Title
 Table 8.1 Specific Heats and Molar Heat Capacities for Some Common Substances at 25°C
Caption
Notes
Keywords
08-TB02
Title
 Table 8.2 Standard Heats of Formation for Some Common Substances at 25°C
Caption
Notes
Keywords
08-TB03
Title
 Table 8.3 Thermochemical Properties of Some Fuels
Caption
Notes
Keywords
08-TB04
Title
 Table 8.4 Caloric Values of Some Foods
Caption
Notes
Keywords
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