Chemistry
Chemical Thermodynamics
Chemical thermodynamics is the study of the energy changes that occur during chemical reactions and the relationships between energy, work, and heat. It provides a framework for understanding and predicting the direction of chemical reactions, as well as the feasibility and spontaneity of these reactions. Key concepts include enthalpy, entropy, and Gibbs free energy, which are used to quantify and analyze these energy changes.
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12 Key excerpts on "Chemical Thermodynamics"
- Nils O. Petersen(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
C H A P T E R 6 The basics of thermodynamics 6.1 SOME BASIC CONCEPTS Thermodynamics refers to the field of chemistry which is concerned with un- derstanding the flow of energy within a system or when a system changes from one state to another. One ultimate purpose of thermodynamics is to predict whether a change will occur spontaneously. The field of thermodynamics is based on three fundamental laws which lead to a set of parameters such as the free energy and the chemical potential, which are key to our understanding of spontaneous change. In contrast to the field of quantum mechanics, the field of thermodynamics is, to a first approximation, not concerned with the detailed structures of the materials, and hence the outcomes become very generally applicable. Our first task is to remind ourselves of some basic concepts of systems and how we describe these. A system is simply that region of space or matter that we are interested in understanding. The surroundings of the system is everything else — in principle, everything else in the universe, but in practice everything else that matters, such as the laboratory in which we study the system. For example, the system could be a gas held in a glass container, with the surroundings being the glass container and everything around it. Similarly, the system could be a solution of molecules in a solvent where the system is the molecules in solution and the surroundings include the solvent, the container and everything around it. We characterize a system by a number of functions (or variables) that tell us something unique about the system. Examples would be the temperature of the system, the pressure of the system, the volume of the system, the mass (or the number of molecules) in the system, and the energy of the system. If the state of the system changes, we expect one or more of these functions to change as well, for example, if the number of molecules in the system changes, 99
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter- 2 Chemical Thermodynamics Chemical Thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics. Chemical Thermodynamics involves not only laboratory measurements of various thermodynamic properties, but also the application of mathematical methods to the study of chemical questions and the spontaneity of processes. The structure of Chemical Thermodynamics is based on the first two laws of ther-modynamics. Starting from the first and second laws of thermodynamics, four equations called the fundamental equations of Gibbs can be derived. From these four, a multitude of equations, relating the thermodynamic properties of the thermodynamic system can be derived using relatively simple mathematics. This outlines the mathematical framework of Chemical Thermodynamics. History J. Willard Gibbs - founder of Chemical Thermodynamics In 1865, the German physicist Rudolf Clausius, in his Mechanical Theory of Heat , suggested that the principles of thermochemistry, e.g. such as the heat evolved in combustion reactions, could be applied to the principles of thermodynamics. Building on the work of Clausius, between the years 1873-76 the American mathematical physicist ____________________ WORLD TECHNOLOGIES ____________________ Willard Gibbs published a series of three papers, the most famous one being the paper On the Equilibrium of Heterogeneous Substances . In these papers, Gibbs showed how the first two laws of thermodynamics could be measured graphically and mathematically to determine both the thermodynamic equilibrium of chemical reactions as well as their tendencies to occur or proceed. Gibbs’ collection of papers provided the first unified body of thermodynamic theorems from the principles developed by others, such as Clausius and Sadi Carnot.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 2 Chemical Thermodynamics Chemical Thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics. Chemical Thermodynamics involves not only laboratory measurements of various thermodynamic properties, but also the application of mathematical methods to the study of chemical questions and the spontaneity of processes. The structure of Chemical Thermodynamics is based on the first two laws of thermodynamics. Starting from the first and second laws of thermodynamics, four equations called the fundamental equations of Gibbs can be derived. From these four, a multitude of equations, relating the thermodynamic properties of the thermodynamic system can be derived using relatively simple mathematics. This outlines the mathematical framework of Chemical Thermodynamics. History J. Willard Gibbs - founder of Chemical Thermodynamics In 1865, the German physicist Rudolf Clausius, in his Mechanical Theory of Heat , suggested that the principles of thermochemistry, e.g. such as the heat evolved in combustion reactions, could be applied to the principles of thermodynamics. Building on the work of Clausius, between the years 1873-76 the American mathematical physicist ________________________ WORLD TECHNOLOGIES ________________________ Willard Gibbs published a series of three papers, the most famous one being the paper On the Equilibrium of Heterogeneous Substances . In these papers, Gibbs showed how the first two laws of thermodynamics could be measured graphically and mathematically to determine both the thermodynamic equilibrium of chemical reactions as well as their tendencies to occur or proceed. Gibbs’ collection of papers provided the first unified body of thermodynamic theorems from the principles developed by others, such as Clausius and Sadi Carnot.
- Peter V. Hobbs(Author)
- 2000(Publication Date)
- Cambridge University Press(Publisher)
2 Chemical Thermodynamics Heat can be released or absorbed during a chemical reaction. This pro-vides a powerful method for studying chemical equilibrium by means of Chemical Thermodynamics. Thermodynamics is based on a few funda-mental postulates, called the first, second, and third laws of thermo-dynamics. We will discuss these laws first, and then apply them to chemical equilibria. 2.1 The first law of thermodynamics; enthalpy In addition to the macroscopic kinetic and potential energy that a body or system as a whole may possess, it also contains internal energy due to the kinetic and potential energy of its molecules or atoms. Increases in internal kinetic energy in the form of molecular motions are manifested as increases in the temperature of the system, while changes in the poten-tial energy of the molecules are caused by changes in their relative configurations. Let us suppose that a system of unit mass takes in a certain quantity of heat energy q (measured in joules). As a result, the system may do a certain amount of external work w (also measured in joules). The excess energy supplied to the system, over and above the external work done by the system, is q - w. Therefore, if there is no change in the macro-scopic kinetic and potential energy of the system, it follows from the principle of conservation of energy that the internal energy of the system must increase by q -w. That is, q - w = u 2 -Mi (2.1) where u x and u 2 are the internal energies of a unit mass of the system before and after the change. In differential form Eq. (2.1) becomes 17 18 Chemical Thermodynamics dq-dw = du (2.2) where dq is the differential increment of heat added to a unit mass of the system, dw the differential increment of work done by a unit mass of the system, and du the differential increment in internal energy of a unit mass of the system. Equations (2.1) and (2.2) are statements of the first law of thermodynamics.
- Anthony R. Philpotts, Jay J. Ague(Authors)
- 2022(Publication Date)
- Cambridge University Press(Publisher)
8 Introduction to Thermodynamics Overview Thermodynamics, the study of energy, is one of the most important subjects in all of science. Historically, it evolved from the desire to understand the efficiency of machines, in particular steam engines. Much of its terminology therefore centers around heat and work, especially work associated with expanding gas. Thermodynamics, however, deals with the transfer of other forms of energy as well, such as that associated with chemical reactions. Although heat and mechanical work done by expanding gas are important in geology, for example in the cooling of magma or the explosion of a volcano, the study of chemical energies is of greatest value to petrology. Thermodynamics is particularly useful in the study of processes that take place within the Earth, where they cannot be observed directly. The ever-increasing availability of thermodynamic data for common minerals, magmas, and fluids has resulted in a rapid growth in the application of thermodynamics to petrology. It is possible, for example, to calculate melting points of minerals, amounts and compositions of minerals crystallizing from magma, temperatures and pressures of metamorphic reactions, and compositions of ore-forming solutions. Computer programs are now routinely used for such calculations, but some knowledge of thermodynamics is essential to understand what the programs are actually doing. Little more than a descriptive treatment of petrology could be given if thermodynamics were omitted. However, an entire book would be required to fully develop all the thermodynamic relations encountered in petrology. In this and the following two chapters, the focus is on the more important fundamental concepts. Physical chemistry and petrologic thermodynamic texts will provide the reader with more extensive coverage (e.g., Zemansky 1943; Wood & Fraser 1977; Powell 1978; Castellan 1983; Atkins & de Paula 2014).
- Daniel Walgraef, J Martinez-mardones, Carlos Hernan Worner(Authors)
- 2000(Publication Date)
- World Scientific(Publisher)
PHYSICO-Chemical Thermodynamics OF MATERIAL SYSTEMS: A REVIEW OP BASIC CONCEPTS AND RESULTS ARMANDO FERNANDEZ GUILLERMET Consejo National de Investigaciones Cientificas y Ttcnicas Centra Atomico Bariloche-Instituto Balseiro 8400 San Carlos de Bariloche-Argentina. E-mail: [email protected] 1 Introduction 1.1 General Considerations Thermodynamics developed from the study of heat-engines and the relations between heat and work. However, after some time, it was recognized that the study of the effects of the thermal and mechanical interactions between the system and the surroundings provides valuable information on the equilibrium properties of the material systems, and on the reactions or transformations which occur. Today, thermodynamics might be considered as a discipline which deals with (i) a wide class of macroscopic properties of material sys-tems, (ii) the way in which these properties are influenced by the thermal, mechanical and chemical interactions with other systems, and (iii) the reac-tions or transformations involved. One of the key variables in the thermodynamic approach is temperature, and, in a certain sense, thermodynamics may be defined as the science dealing with the forms in which the properties of matter are modified by the changes in temperature. In particular, for material systems, it is interesting to determine the effects of temperature upon the equilibrium properties of a given structure, and to explore the possibility of inducing changes of structure by suitable temperature variations. The question of identifying the most stable structure for given external conditions is usually known as the Phase Stability Problem, which is often considered as a central problem in the study of material systems. Classical thermodynamics developed without referring to any particular model of the structure of matter.
eBook - PDF- Pierluigi Zotto, Sergio Lo Russo, Paolo Sartori(Authors)
- 2022(Publication Date)
- Società Editrice Esculapio(Publisher)
General Concepts of Thermodynamics 14.1 Introduction The statistical description of the behaviour of gases expressed by the kinetic theory of gases or by more advanced models of statistical mechanics is not the only possible ap- proach. It is in fact possible to abstract from a microscopic description by identifying some macroscopic variables which can anyway provide full information about the state of a solid, liquid or gaseous substance. This way to represent the behaviour of matter is the basis of Thermodynamics. Definitions and general concepts of thermodynamics are introduced into this chapter, focussing in particular on heat, and the discipline, called calorimetry, which studies it. 14.2 Thermodynamic System Thermodynamics studies the description of the evolution of a thermodynamic system, defined as a body or a group of bodies whose chemical composition is well defined. Everything which does not belong to a thermodynamic system is its thermodynamic environment. Every chemical species which belongs to a thermodynamic system is a constituent of the system. A thermodynamic system is called a homogeneous system if its chemical composition and its physical properties are the same everywhere in it: in such a case a thermodynamic system has got only one phase, which can be solid, liquid or gaseous. The macroscopic quantities which completely specify its state, called thermodynamic state, are variables called thermodynamic coordinates or variables of state. These quantities must be measurable physical quantities, such as, for instance, pressure, volume, tempera- ture, chemical concentrations, electric or magnetic states of matter. The state of a system is known only once all its thermodynamics coordinates are exactly defined, meaning that no thermodynamic coordinate can have a different value in different parts of the thermodynamic system.
eBook - PDF- Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
G = H - TS We will look at these thermodynamic functions in greater detail, and provide exact definitions, in the appropriate sections of this chapter. For now, it is sufficient to state that the value of Gibbs energy, G, allows us to predict spontaneity. We can liken a spontaneous change to a ball at the top of a hill — once pushed, it will roll spontaneously down the hill until it reaches the bottom, the point of minimum energy. CHAPTER 8 Chemical Thermodynamics 349 In the same way, we will see that chemical reactions proceed in the direction that leads to a decrease in the Gibbs energy of the system. We will also see that overall chemical and physical change will cease once the Gibbs energy of the system is minimised, and that, under these conditions, the system is at equilibrium. 8.2 Thermodynamic concepts LEARNING OBJECTIVE 8.2 Use the terminology and units of Chemical Thermodynamics. Before we begin our study of Chemical Thermodynamics, we need to discuss some important thermody- namic concepts. Heat and temperature Arguably the most important and indeed most familiar thermodynamic term, heat (q), is perhaps the most conceptually difficult. Heat is the energy that is transferred as the result of a temperature difference. If two bodies having different temperatures are brought into direct contact, there will be heat flow from the hotter to the colder body, until both are at the same temperature. As we will see, we cannot actually measure heat directly. The definition of temperature also follows from the above; two bodies have the same temperature if they are in thermal equilibrium; that is, there is no heat flow between them when they are in direct contact. It is important to note that the thermodynamic temperature (sometimes called the absolute temperature) scale is used in nearly all thermodynamic calculations.
eBook - PDFChemistry
Structure and Dynamics
- James N. Spencer, George M. Bodner, Lyman H. Rickard(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
594 Chapter Thirteen Chemical Thermodynamics 13.1 Spontaneous Chemical and Physical Processes 13.2 Entropy and Disorder 13.3 Entropy and the Second Law of Thermodynamics 13.4 Standard-State Entropies of Reaction 13.5 The Third Law of Thermodynamics 13.6 Calculating Entropy Changes for Chemical Reactions 13.7 Gibbs Free Energy 13.8 The Effect of Temperature on the Free Energy of a Reaction 13.9 Beware of Oversimplifications 13.10 Standard-State Free Energies of Reaction 13.11 Equilibria Expressed in Partial Pressures 13.12 Interpreting Standard-State Free Energy of Reaction Data 13.13 The Relationship between Free Energy and Equilibrium Constants 13.14 The Temperature Dependence of Equilibrium Constants 13.15 Gibbs Free Energies of Formation and Absolute Entropies 13.1 Spontaneous Chemical and Physical Processes No one is surprised when a cup of hot coffee gradually loses heat to its surround- ings as it cools, or when the ice in a glass of lemonade melts as it absorbs heat from its surroundings. But we would be surprised if a cup of coffee suddenly grew hotter until it boiled, or if the water in a glass of lemonade suddenly froze on a hot summer’s day. In a similar fashion, no one should be surprised when a piece of zinc metal dissolves in a strong acid to give bubbles of hydrogen gas that rise through the solution to escape from the top surface of the solution. But if we saw a video in which H 2 bubbles formed on the surface of a solution and then sank through the solution until they disappeared, while a strip of zinc metal formed in the middle of the solution, we would conclude that the video was being run backward. Philosophers have argued that conventional wisdom gives us some idea of time’s arrow; the direction in which time flows. Time’s arrow is the direction in which a process is said to be spontaneous. Many chemical and physical processes proceed in a direction in which they are said to be spontaneous.
eBook - PDFChemical Thermodynamics
Basic Concepts and Methods
- Irving M. Klotz, Robert M. Rosenberg(Authors)
- 2008(Publication Date)
- Wiley-Interscience(Publisher)
In discussing these fundamental postulates, which are essentially concise descriptions based on much experience, we will emphasize at all times their application to chemical, geological, and biological systems. However, first we must define a few of the basic concepts of thermodynamics. 3.1 DEFINITIONS Critical studies of the logical foundations [1] of physical theory have emphasized the care that is necessary in defining fundamental concepts if contradictions between theory and observation are to be avoided. Our ultimate objective is clarity and pre- cision in the description of the operations involved in measuring or recognizing the concepts. First let us consider a very simple example—a circle. At a primitive stage we might define a circle by the statement, “A circle is round.” Such a definition would be adequate for children in the early grades of elementary school, but it could lead to long and fruitless arguments as to whether particular closed curves are circles. A much more satisfactory and refined definition is “a group of points in a plane, all of which are the same distance from an interior reference point called the center.” This definition describes the operations that need to be carried out to generate a Chemical Thermodynamics: Basic Concepts and Methods, Seventh Edition. Edited by Irving M. Klotz and Robert M. Rosenberg Copyright # 2008 John Wiley & Sons, Inc. 29 circle or to recognize one. The development of mature scientific insight involves, in part, the recognition that an early “intuitive understanding” at the primitive level often is not sound and sometimes may lead to contradictory conclusions from two apparently consistent sets of postulates and observations. The operational approach to the definition of fundamental concepts in science has been emphasized by Mach, Poincare, and Einstein and has been expressed in a very clear form by Bridgman [2].
eBook - PDF- Martinus A.J.S. van Boekel(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
A suitable measure for the quality of energy is called exergy, and exergy can be lost. We will not discuss this any further here, except to state that exergy calculations are a useful tool for the food industry to design processes as ef fi cient as possible with regard to energy conversion. The second law of thermodynamics states that there is only one direction for irreversible processes, namely those resulting in an increase in entropy S in an isolated system and the entropy is maximal at the equilibrium state. If changes occur spontaneously (i.e., without any work being done on the system) the total entropy of the system and its surroundings (i.e., of the universe) must increase. This does not mean that the entropy of a system cannot decrease; this actually happens during crystallization or condensation, or in a refrigerator, but the requirement remains that the total entropy of the universe must increase. However, the entropy of an isolated system cannot decrease, as will be made clear shortly. The change in entropy determines whether or not a reaction will occur; the energy changes in a reaction have an effect in as much as they increase or decrease the entropy of the system and its surroundings. The dispersal of energy is the ‘‘ driving force ’’ for physical as well as Chemical Thermodynamics in a Nutshell 3 -11 chemical reactions but it is of a probabilistic nature. That means that it is possible for energy to be concentrated temporarily in a system, for instance because there is some barrier that prevent things from happening (otherwise life would not be possible!). This does not con fl ict with the second law of thermodynamics. We will come back to this when discussing kinetics. A frequently used term in relation to entropy is spontaneous process (Table 3.4).
eBook - PDFChemistry
An Industry-Based Introduction with CD-ROM
- John Kenkel, Paul B. Kelter, David S. Hage(Authors)
- 2000(Publication Date)
- CRC Press(Publisher)
1 / 2 1 / 2 C 6 H 12 O 6 s ( ) 6O 2 g ( ) 6CO 2 g ( ) 6H 2 O g ( ) → NH 3 g ( ) 2O 2 g ( ) HNO 3 aq ( ) H 2 O l ( ) → Introduction to Thermodynamics 341 FIGURE 13.2 When glucose is burned, some of the potential energy stored in the bonds is converted to kinetic energy and released as kinetic energy. Chemistry Professionals at Work CPW Box 13.2 T HERMAL A NALYSIS he identity and purity of drugs can be indicated by precisely controlling thermodynamic processes, such as melting or boiling. Thus the determination of melting points and boiling points can be involved in the standard methods for analyzing for drugs. Broadly speaking, thermal analysis is the observation of properties while the temperature is changed. Techniques include differential scanning calorimetry ( DSC ) , differential thermal analysis (DTA) , and thermogravimetric analysis (TGA). For Homework: Research the three thermal methods of analysis mentioned above. Write a report giving brief but thorough descriptions of each, detailing exactly what properties are measured and what observations are made by the chemistry professional. T 342 Chemistry: An Industry-Based Introduction with CD-ROM 13.3 Types of Energy and Energy Exchange 13.3.1 Heat and Its Relationship to Temperature Kinetic energy can be manifested in a variety of ways. When particles move, they possess heat energy . A measure of the average kinetic energy of the particles of a substance is called temperature . Temperature is not a measure of the total amount of heat in a system. Rather, it is a measure of the average kinetic energy of the system. Thus, a hot penny at a temperature of 1000°C has less heat energy than a lake at 20°C, because the penny is very small compared to the lake, even though it has a higher temperature. Please review the temperature scale conversions in Section 7.7—we will use temperature often, but not as a measure of heat content. Instead, we will use it as a measure of energy exchange between systems.
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