Book contents
- Frontmatter
- Contents
- Preface
- 1 What is thermodynamics?
- 2 Defining our terms
- 3 The first law of thermodynamics
- 4 The second law of thermodynamics
- 5 Getting data
- 6 Some simple applications
- 7 Ideal solutions
- 8 Fugacity and activity
- 9 The equilibrium constant
- 10 Real solutions
- 11 The phase rule
- 12 Redox reactions
- 13 Equations of state
- 14 Solid solutions
- 15 Electrolyte solutions
- 16 Rock–water systems
- 17 Phase diagrams
- 18 Process modeling
- Appendices
- References
- Index
4 - The second law of thermodynamics
- Frontmatter
- Contents
- Preface
- 1 What is thermodynamics?
- 2 Defining our terms
- 3 The first law of thermodynamics
- 4 The second law of thermodynamics
- 5 Getting data
- 6 Some simple applications
- 7 Ideal solutions
- 8 Fugacity and activity
- 9 The equilibrium constant
- 10 Real solutions
- 11 The phase rule
- 12 Redox reactions
- 13 Equations of state
- 14 Solid solutions
- 15 Electrolyte solutions
- 16 Rock–water systems
- 17 Phase diagrams
- 18 Process modeling
- Appendices
- References
- Index
Summary
Introduction
The first sentence of Gibbs' (1875) classic memoir “On the equilibrium of heterogeneous substances” is
The comprehension of the laws which govern any material system is greatly facilitated by considering the energy and entropy of the system in the various states of which it is capable.
Given the fact that virtually all of equilibrium thermodynamics can be derived by doing exactly that, as Gibbs did, this must rank as one of the world's great understatements. In this chapter, we begin to explore what Gibbs was referring to. By considering “the laws which govern any material system,” we should be able to find the answers to the questions we posed in Chapter 1.
The problem restated
Having taken a couple of chapters to get our terminology settled and to get used to discussing energy changes in systems, we must now get back to our main problem – what determines whether chemical processes will go or not go? Our method of determining this might be considered a bit simple-minded – we will simply determine the “chemical energy” differences between equilibrium states. Processes can take place spontaneously if they are in the direction of lowering the chemical energy. They cannot take place spontaneously in the opposite direction.
We have seen that the first great principle of energy transfers is that energy never disappears; it simply takes on different forms. It is the second principle or law that more directly addresses our main problem.
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- Information
- Thermodynamics of Natural Systems , pp. 65 - 110Publisher: Cambridge University PressPrint publication year: 2005