Chemistry
Energy Diagrams
Energy diagrams in chemistry illustrate the energy changes that occur during a chemical reaction. They typically show the energy of the reactants, the activation energy barrier, and the energy of the products. The diagram helps visualize the energy changes and the pathway of the reaction, providing insights into the reaction's feasibility and speed.
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3 Key excerpts on "Energy Diagrams"
eBook - PDF- Young, William Vining, Roberta Day, Beatrice Botch(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
Vasilyev/Shutterstock.com Thermochemistry Unit Outline 10.1 Energy 10.2 Enthalpy 10.3 Energy, Temperature Changes, and Changes of State 10.4 Enthalpy Changes and Chemical Reactions 10.5 Hess’s Law 10.6 Standard Heats of Reaction In This Unit… This unit begins an exploration of thermochemistry, the study of the role that energy in the form of heat plays in chemical processes. We inves-tigate the energy changes that take place during phase changes and the chemical reactions you have studied previously and learn why some chemical reactions occur while others do not. In Electromagnetic Radiation and the Electronic Structure of the Atom (Unit 3), you stud-ied energy changes at the molecular level and the consequences those energy changes have on the properties of atoms and elements. 10 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 Unit 10 Thermochemistry 272 10.1 Energy 10.1a Energy and Energy Units Chemical reactions involve reactants undergoing chemical change to form new substances, products. reactants S products What is not apparent in the preceding equation is the role of energy in a reaction. For many reactions, energy, often in the form of heat, is absorbed—that is, it acts somewhat like a reactant. You might write an equation for those reactions that looks like this: energy 1 reactants S products In other reactions, energy is produced—that is, it acts like a product: reactants S products 1 energy In Chemistry, Matter on the Atomic Scale (Unit 1), we defined energy (the ability to do work) and work (the force involved in moving an object some distance). From a chemist’s point of view, energy is best viewed as the ability to cause change, and thermochemistry is the study of how energy in the form of heat is involved in chemical change.
eBook - PDFChemical Energy and Exergy
An Introduction to Chemical Thermodynamics for Engineers
- Norio Sato(Author)
- 2004(Publication Date)
- Elsevier Science(Publisher)
CHAFFER 11 EXERGY DIAGRAM The effective use of energy in a chemical plant results from employing the combination of processes that consumes the least amount of exergy as a whole in manufacturing the products. To examine the flow of exergy the diagram that visualizes the exergy balance in manufacturing processes has practically been used for the purpose of improving the exergy efficiency in the plants. Furthermore, a novel concept of exergy vectors has recently been brought forth to evaluate the exergy efficiency of various processes on an enthalpy-exergy diagram. By means of exergy vectors the minimum exergy thermodynamically required for a manufacturing process may be estimated in the diagram. This chapter describes the principle of exergy vector diagrams and their application to basic processes such as heating-cooling, compression-expansion, separation- mixing, and chemical reactions. 11.1. Efficiency in the Use of Energy. In chemical manufacturing processes there are a flow of substances (materials) Z ni , a flow of work W, and a flow of heat Q, which are all accompanied by a flow of exergy E. The inlet flow of exergy dE+/dt (positive sign) into and the outlet flow of exergy dE/dt (negative sign) out of an open system of chemical processes at a temperature T are given by Eqs. 11.1 and 11.2, respectively: dE+ dn~+ dW§ ( T To) dQ+ dt = ~'+ -dT e'+ + --d~ + T dr' (11.1) dE_ dn, dW (T dQ_ (11.2) a,' where n i is the number of moles, ei is the molar exergy of substance i, and TOis the exergy reference temperature. On the right hand side in Eqs. 11.1 and 11.2 the first term is the 116 EXERGY DIAGRAM exergy flow of substances, the second term is the exergy flow of work, and the third term is the exergy flow of heat. Figure 11.1 shows the flow of exergy through an open system at a temperature T in which physical and chemical processes are taking place in irreversible modes.
eBook - PDFChemistry
The Molecular Nature of Matter
- Neil D. Jespersen, Alison Hyslop(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
Thermochemistry is part of the science of thermodynamics, the study of energy transfer and energy transformation. Thermodynamics allows scientists to predict whether a proposed physical change or chem- ical reaction can occur under a given set of conditions. It is an essential part of chemistry (and all of the natural sciences). We’ll continue our study of thermodynamics in Chapter 18. CHAPTER OUTLINE 6.1 Energy: The Ability to Do Work 6.2 Heat, Temperature, and Internal Energy 6.3 Measuring Heat 6.4 Energy of Chemical Reactions 6.5 Heat, Work, and the First Law of Thermodynamics 6.6 Heats of Reaction 6.7 Thermochemical Equations 6.8 Hess’s Law 6.9 Standard Heats of Reaction Energy and Chemical Change David Willman/123 RF CHAPTER 6 260 CHAPTER 6 Energy and Chemical Change LEARNING OBJECTIVES After reading this chapter using your active reading skills, you should be able to: • explain the difference between potential and kinetic energy and explain the law of conservation of energy. • explain the connection between temperature, energy, and the concept of a state function. • determine the amount of heat exchanged from the temperature change of an object. • describe the energy changes in exothermic and endothermic reactions. • state the first law of thermodynamics and explain how it applies to chemistry. • explain the difference between the heat of reaction obtained at constant pressure and the heat of reaction at constant volume. • describe the assumptions and utility of thermochemical equations. • use Hess's law to determine the enthalpy of a reaction. • determine and use standard heats of formation to solve problems. CONNECTING TO THE LEARNING OBJECTIVES These suggestions are here to help you learn the chapter material. Writing notes while studying is known to be the best way to remember what you are studying.
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