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Key Concepts PowerPoint

Chapter 17
Thermodynamics: Entropy, Free Energy, and Equilibrium

 
17-01
Title
Spontaneous vs. nonspontaneous
Caption
Figure 17.1 When the stopcock is opened, the gas in bulb A expands spontaneously into evacuated bulb B to fill all the available volume. The reverse process, compression of the gas, is nonspontaneous.
Notes
Spontaneous versus nonspontaneous processes
Keywords
spontaneous process
17-02
Title
Rate of spontaneous processes
Caption
Figure 17.2 (a) The rusting of this ship is a spontaneous reaction, but it occurs slowly. (b) A spontaneous reaction occurs slowly if it has a high activation energy Ea.
Notes
The magnitude of the activation energy affects the rate at which a spontaneous process willl proceed
Keywords
activation energy, spontaneous process, rate
17-03
Title
Entropy
Caption
Figure 17.3 Molecular randomness—and thus entropy—increases when a solid melts and when a liquid vaporizes. Conversely, randomness and entropy decrease when a vapor condenses and when a liquid freezes. Note the sign of DS for each process.
Notes
Entropy as a measure of molecular randomness
Keywords
entropy, randomness
17-04
Title
Entropy in reactions
Caption
Figure 17.4 Molecular randomness—and thus entropy—increases when a reaction results in an increase in the number of gaseous particles. For example, DS is positive for decomposition of N2O4 to NO2 and is negative for formation of N2O4 from NO2.
Notes
Production of a greater number of moles of gas particles results in greater molecular randomness
Keywords
entropy, randomness
17-05
Title
Dissolution and entropy
Caption
Figure 17.5 When NaCl dissolves in water, the crystal breaks up, and the Na+and Cl-ions are surrounded by hydrating water molecules. The polar H2O molecules are oriented such that the partially negative O atoms are near the cations and the partially positive H atoms are near the anions. Disruption of the crystal increases the entropy, but the hydration process decreases the entropy. For dissolution of NaCl, the net effect is an entropy increase.
Notes
Net changes in entropy with respect to disruption of the crystal lattice and the hydration of the ions in solution
Keywords
entropy, dissolution
17-05-01UN
Title
Key Concept Problem 17.2
Caption
Consider the gas-phase reaction of A2 molecules (red) with B atoms (blue).
Notes
Key Concept Problem 17.2
Keywords
entropy
17-05-02UN
Title
Key Concept Problem 17.3
Caption
Consider the gas-phase reaction of AB3 and A2 molecules.
Notes
Key Concept Problem 17.
Keywords
entropy
17-06
Title
Entropy and probability
Caption
Figure 17.6 A hypothetical crystal containing 20 CO molecules. In (a), the molecules are arranged in a perfectly ordered “heads-up” structure. In (b), the molecules are arranged randomly in one of the 220 ways in which the disordered structure can be obtained.
Notes
Entropy and probability
Keywords
entropy, probability
17-07
Title
Entropy and temperature
Caption
Figure 17.7 (a) A substance at a higher temperature has greater molecular motion, more disorder, and greater entropy than (b) the same substance at a lower temperature.
Notes
Increased molecular motion results in greater entropy
Keywords
entropy, temperature
17-08
Title
Entropy and temperature
Caption
Figure 17.8 The entropy of a pure substance, equal to zero at 0 K, shows a steady increase with rising temperature, punctuated by discontinuous jumps in entropy at the temperatures of the phase transitions.
Notes
Entropy of a system as a function of temperature
Keywords
entropy, temperature
17-09
Title
Entropy of the surroundings
Caption
Figure 17.9 (a) When an exothermic reaction occurs in the system (DH < 0), the surroundings gain heat and their entropy increases (DSsurr > 0). (b) When an endothermic reaction occurs in the system (DH > 0), the surroundings lose heat and their entropy decreases (DSsurr < 0).
Notes
Entropy of the surroundings as a function of the enthalpy change of the system
Keywords
entropy, enthalpy, spontaneity
17-09-04UN
Title
Key Concept Problem 17.9
Caption
What are the signs (+, -, or 0) of DH, DS, and DG for the following spontaneous reaction of A atoms (red) and B atoms (blue)?
Notes
Key Concept Problem 17.9
Keywords
enthalpy, entropy, free-energy, spontaneity
17-09-05UN
Title
Hypothetical process and free-energy
Caption
The standard free-energy change applies to a hypothetical process that assumes that the reactants are separate from the products. However, in a real process, often the reactants and products are mixed together in the same vessel.
Notes
The meaning of standard free-energy and hypothetical chemical process
Keywords
free-energy
17-09-06UN
Title
Real process and free-energy
Caption
For the real process, when reactants and products are present in a mixture, the free-energy change indicates which direction the equilibrium lies, but does not give information concerning the rate of the reaction.
Notes
The meaning of standard free-energy and a real chemical process
Keywords
17-09-07UN
Title
Key Concept Problem 17.11
Caption
Consider the following endothermic decomposition of AB2 molecules.
Notes
Key Concept Problem 17.11
Keywords
entropy, enthalpy, spontaneity
17-09-08UN
Title
Key Concept Problem 17.14
Caption
Consider the following gas-phase reaction of A2 (red) and B2 (blue) molecules.
Notes
Key Concept Problem 17.14
Keywords
free-energy
17-10
Title
Free energy and equilibrium
Caption
Figure 17.10 The total free energy of a reaction mixture as a function of the progress of the reaction. Beginning with either pure reactants or pure products, the free energy decreases (DG is negative) as the system moves toward equilibrium. The graph is drawn assuming that the pure reactants and pure products are in their standard states and that DG° for the reaction is negative so the equilibrium composition is rich in products.
Notes
Free energy and equilibrium
Keywords
free energy, equilibrium
17-10-01UN
Title
Industrial synthesis of methanol
Caption
Space-filling models showing the industrial synthesis of methanol from carbon monoxide and hydrogen gas.
Notes
Structures of carbon monoxide, hydrogen, and methanol for Worked Example 17.9
Keywords
free-energy, equilibrium, methanol
17-10-040UN
Title
Key Concept Summary
Caption
Thermodynamics: Entropy, Free Energy, and Equilibrium key concept summary.
Notes
Key concept summary for Chapter 17
Keywords
key concept, summary
17-10-05UN
Title
Key Concept Problem 17.20
Caption
Ideal gases A (red spheres) and B (blue spheres) occupy two separate bulbs. The contents of both bulbs constitute the initial state of an isolated system. Consider the process that occurs when the stopcock is opened.
Notes
Key Concept Problem 17.20
Keywords
key concept, spontaneity, enthalpy, entropy
17-10-06UN
Title
Key Concept Problem 17.21
Caption
What are the signs (+, -, or 0) of DH, DS, and DG for the spontaneous sublimation of a crystalline solid? Explain.
Notes
Key Concept Problem 17.21
Keywords
key concept, enthalpy, entropy, free-energy
17-10-07UN
Title
Key Concept Problem 17.22
Caption
What are the signs (+, -, or 0) of DH, DS, and DG for the spontaneous condensation of a vapor to a liquid? Explain.
Notes
Key Concept Problem 17.22
Keywords
key concept, enthalpy, entropy, free-energy
17-10-08UN
Title
Key Concept Problem 17.23
Caption
An ideal gas is compressed at constant temperature. What are the signs (+, -, or 0) of DH, DS, and DG for the process? Explain.
Notes
Key Concept Problem 17.23
Keywords
key concept, enthalpy, entropy, free-energy
17-10-09UN
Title
Key Concept Problem 17.24
Caption
Consider the following spontaneous reaction of A2 molecules (red) and B2 molecules (blue).
Notes
Key Concept Problem 17.24
Keywords
key concept, enthalpy, entropy, free-energy
17-10-10UN
Title
Key Concept Problem 17.25
Caption
Consider the dissociation reaction A2(g) <=> 2 A(g). The following pictures represent two possible inital states and the equilibrium state of the system.
Notes
Key Concept Problem 17.25
Keywords
reaction quotient, equilibrium, thermodynamics
17-10-11UN
Title
Key Concept Problem 17.27
Caption
Consider the following graph of the total free energy of reactants and products versus reaction progress for general reaction, Reactants --> Products
Notes
Key Concept Problem 17.27
Keywords
key concept, free energy
17-10-12UN
Title
Key Concept Problem 17.28
Caption
The following pictures represent equilibrium mixtures for the interconversion of A molecules (red) and X, Y, or Z molecules (blue).
Notes
Key Concept Problem 17.28
Keywords
key concept, free-energy
17-10-13UN
Title
Key Concept Problem 17.29
Caption
The following pictures represent the composition of the equilibrium mixture at 25oC and 45oC for the reaction A <=> B, where A molecules are represented by red spheres, and B molecules by blue spheres.
Notes
Key Concept Problem 17.29
Keywords
key concept, enthalpy, entropy
17-TB01
Title
Table 17.1 Standard Molar Entropies for Some Common Substances at 25°C
Caption
Notes
Keywords
17-TB02
Title
Table 17.2 Signs of Enthalpy, Entropy, and Free-Energy Changes and Reaction Spontaneity for a Reaction at Constant Temperature and Pressure
Caption
Notes
Keywords
17-TB02.01UN
Title
CO(g) Fe(s)
Caption
CO(g) Fe(s)
Notes
Keywords
17-TB03
Title
Table 17.3 Standard Free Energies of Formation for Some Common Substances at 25°C
Caption
Notes
Keywords
17-TB04
Title
Table 17.4 Relationship Between the Standard Free-Energy Change and the Equilibrium Constant for a Reaction: ŪG° = -RT In K
Caption
Notes
Keywords
17-TB04.01UN
Title
bp Liquid (°C) (kJ/mol)
Caption
bp Liquid (°C) (kJ/mol)
Notes
Keywords

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