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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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