Chemistry
Chemical Reactions
Chemical reactions involve the transformation of substances into new compounds through the breaking and forming of chemical bonds. This process often involves the release or absorption of energy. Chemical reactions are described by chemical equations, which show the reactants and products involved, and are fundamental to understanding the behavior of matter in the universe.
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12 Key excerpts on "Chemical Reactions"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
Chapter 8 Chemical Reaction A thermite reaction using ferric oxide A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical Reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, viz. heat, light or electricity. Classically, Chemical Reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. ___________________WORLD TECHNOLOGIES____________________ The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical Reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical Reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products and reaction conditions. Different Chemical Reactions are used in combination in chemical synthesis in order to obtain a desired product. In biochemistry, series of Chemical Reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions impossible under ordinary conditions are performed within a cell. History Antoine Lavoisier developed the theory of combustion as a chemical reaction with oxygen Chemical Reactions such as combustion in the fire, fermentation and the reduction of ores to metals were known since antiquity.
eBook - PDF- Luca Palmeri, Alberto Barausse, Sven Erik Jorgensen(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
131 © 2008 Taylor & Francis Group, LLC 9 Chemical Reactions 9.1 Introduction The term chemical process is used to indicate a sequence of one or more operations achieving the transformation of chemicals. Chemical processes fall into three broad categories: processes performed in a chemical laboratory, industrial chemical processes carried out on an industrial scale, and natural chemical processes. Natural chemical processes are carried out in nature ide-ally without human action. These include, for example, the chemical processes that occur naturally in living organisms (including metabolism and photosyn-thesis) and the reactions of biodegradation. Chemical laboratory and industrial processes refer to chemical processes developed and engineered by man. Generally, a chemical reaction is a transformation of matter that occurs with-out measurable changes in mass, in which one or more initial chemical ele-ments change their structure and composition to create new products through the formation or breaking of chemical bonds involving an atom’s outer elec-trons. The chemical compounds present at the beginning of the reaction are called reagents or reactants ; whereas those obtained at the end of the reaction are called the reaction products . The phenomenon taking place during a chemi-cal reaction can be represented by a chemical equation.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Research World(Publisher)
Chapter 10 Chemical Reaction A thermite reaction using ferric oxide A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical Reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, viz. heat, light or electricity. Classically, Chemical Reactions encompass changes that strictly __________________WORLD TECHNOLOGIES___________________ involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical Reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical Reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products and reaction conditions. Different Chemical Reactions are used in combination in chemical synthesis in order to obtain a desired product. In biochemistry, series of Chemical Reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions impossible under ordinary conditions are performed within a cell. History Antoine Lavoisier developed the theory of combustion as a chemical reaction with oxygen Chemical Reactions such as combustion in the fire, fermentation and the reduction of ores to metals were known since antiquity.
eBook - PDF- Ageetha Vanamudan(Author)
- 2023(Publication Date)
- Delve Publishing(Publisher)
Chemical Reactions CHAPTER5 CONTENTS 5.1 History of Chemical Reactions ........................................................... 77 5.2 Chemical Reactions of Various Types ................................................. 79 5.3 Several Theories Exist to Explain Acid-Base Reactions ........................ 87 5.4 Photolysis Reactions .......................................................................... 92 Introduction to Molecular Science 76 A chemical reaction occurs when one or more reactants are converted into one or more distinct products. Compounds and chemical elements are examples of substances. By rearranging the atoms of the reactants, Chemical Reactions produce a wide range of products. Chemical Reactions are crucial in contemporary culture, technology, and even life itself. Fuel combustion, iron smelting, glass, and pottery manufacture, beer production, and the creation of wine and cheese are some examples of chemical processes that have been employed for millennia. In addition to the Chemical Reactions that occur in the earth’s crust, atmosphere, and seas, several complex processes occur in all living systems. It is necessary to distinguish between Chemical Reactions and physical changes. Physical transitions include ice melting into water and water evaporating to create vapor (Rastogi & Sani, 2011). A substance’s physical properties may change throughout metamorphosis, but its chemical identity does not. Water (H 2 O ) is the same substance regardless of its physical state since each molecule includes two hydrogen atoms and one oxygen atom. When water reacts with sodium metal (Na), it produces molecular hydrogen (H 2 ) and sodium hydroxide (NaOH). This denotes the occurrence of a chemical reaction or change. Understanding the fundamentals of chemical interactions. Figure 5.1: Chemical analysis of chemical reactants. Source: By No machine-readable author provided. Burn~commonswiki as- sumed (based on copyright claims).
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
WT ____________________ WORLD TECHNOLOGIES ____________________ Chapter 4 Chemical Reaction A thermite reaction using ferric oxide A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical Reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, viz. heat, light or electricity. Classically, Chemical Reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. WT ____________________ WORLD TECHNOLOGIES ____________________ The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical Reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical Reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products and reaction conditions. Different Chemical Reactions are used in combination in chemical synthesis in order to obtain a desired product. In biochemistry, series of Chemical Reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions impossible under ordinary conditions are performed within a cell. History Antoine Lavoisier developed the theory of combustion as a chemical reaction with oxygen Chemical Reactions such as combustion in the fire, fermentation and the reduction of ores to metals were known since antiquity.
eBook - PDF- C N R Rao(Author)
- 2009(Publication Date)
- World Scientific(Publisher)
6 Chemical Reactions 226 Understanding Chemistry Chemistry is a study of reactions between substances. It is therefore important to understand the nature of Chemical Reactions. One can make new substances by making use of various Chemical Reactions. We shall try to understand how reactions can be associated with rates, and the factors that influence the rates. We then survey a few simple types of reactions and show how chemists innovate new strategies for making molecules using catalysts and new routes for synthesis. 6.1 Which reactions occur? Some reactions occur spontaneously. We can understand this by analogy with potential energy. If we store water in a dam at the top of a hill, it has high potential energy. If there were no dam, water would have flowed down. Objectives • In this lesson, we shall try to understand why and how Chemical Reactions occur and the factors that affect them. • We then go through different types of reactions, which include catalysis and light-induced reactions. • A combination of Chemical Reactions is necessary to prepare complex compounds. Chemists continue to discover new ways of assembling molecules. The supramolecular route provides a rich resource for new molecular systems. Chemical Reactions 227 increasing chemical potential energy increasing stability reactants products direction of spontaneous reaction In other words, the products have to be more stable than the reactants. One may, therefore, say that when energy is released in a chemical reaction, it will be spontaneous. This is the case of exothermic reactions. Thus, combustion (burning) is a spontaneous reaction. Remember combustion is associated with the release of heat (energy). Chemical Reactions occur spontaneously when the potential energy of the products is lower than the potential energy of the reactants. 228 Understanding Chemistry 6.2 Chemical equilibrium We used the word equilibrium when describing states of substances in Lesson 1.
eBook - PDF- Stanley E. Manahan(Author)
- 2009(Publication Date)
- CRC Press(Publisher)
Among the of the basic chemical calculations early in a beginning chemistry course. Among the most important of these are the calculations of the quantities of substances consumed most important of these are the calculations of the quantities of substances consumed or produced in a chemical reaction. Such calculations are classified as or produced in a chemical reaction. Such calculations are classified as stoichiometry stoichiometry . . Heat is normally evolved or taken up in the course of a chemical reaction. The cal-Heat is normally evolved or taken up in the course of a chemical reaction. The cal-culation of the quantity of heat involved in a reaction falls in the branch of chemistry culation of the quantity of heat involved in a reaction falls in the branch of chemistry called called thermochemistry thermochemistry . 5.2. THE INFORMATION IN A CHEMICAL EQUATION 5.2. THE INFORMATION IN A CHEMICAL EQUATION Chemical Reactions Chemical Reactions A chemical reaction is a process involving the breaking and/or formation of A chemical reaction is a process involving the breaking and/or formation of chemical bonds and a change in the chemical composition of the materials partici-chemical bonds and a change in the chemical composition of the materials partici-pating in the reaction. A chemical reaction might involve the combination of two pating in the reaction. A chemical reaction might involve the combination of two elements to form a compound. An example of this is the reaction of elemental hydro-elements to form a compound. An example of this is the reaction of elemental hydro-gen and oxygen to produce the compound water. Passage of an electrical current gen and oxygen to produce the compound water. Passage of an electrical current through water can cause the compound to break down and produce elemental hydro-through water can cause the compound to break down and produce elemental hydro-gen and oxygen.
eBook - PDF- David A. Ucko(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
You are already familiar with some chemical re-actions. The rusting of iron, the burning of wood, and the digesting of food all involve chemical change. All compounds are formed by Chemical Reactions. The same com-pound can be formed by several different Chemical Reactions. But re-gardless of how a particular compound is made, its composition is always the same. This observation is summarized by the law of definite 250 Chemical Reactions / 9.2 CHEMICAL EQUATIONS proportions: a given compound always contains its component ele-ments in fixed proportions by weight. The law, illustrated in the dis-cussion of percentage composition in Section 8.6, follows from the atomic theory. A compound consists of molecules or formula units, which are fixed combinations of atoms or ions, joined by bonds formed through a chemical reaction. For example, the compound water con-sists of molecules of H 2 0 . No matter how water is made or where it is found, it always contains two hydrogen atoms for every one oxygen atom. Mixtures, on the other hand, consist of substances that have not reacted with each other. There are no chemical bonds formed between the components in a mixture, and the mixture's composition therefore is not fixed. 9.2 A chemical equation is a shorthand representation of a chemical re-CHEMICAL action. Using the formulas of the substances involved in the reaction, EQUATIONS the chemical equation summarizes the chemical change that takes place. We can think of chemical equations as chemical sentences. We write them by following certain rules, just as we do when we write sentences in English (see Figure 9-2). The equation for the reaction of iron and sulfur is: Fe^j_S FeS reactants product The starting substances, called reactants, are separated from the new substance, called the product, by an arrow. The arrow shows the di-rection of chemical change by pointing from the reactants to the prod-ucts.
eBook - PDFChemistry for Today
General, Organic, and Biochemistry
- Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
(Section 5.7) 5 Classify reactions as exothermic or endothermic. (Section 5.8) 6 Use the mole concept to do calculations based on chemical reaction equations. (Section 5.9) 7 Use the mole concept to do calculations based on the limiting-reactant principle. (Section 5.10) 8 Use the mole concept to do percentage-yield calculations. (Section 5.11) Nastasic/E+/Getty Images Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Chemical Reactions 139 IN PREVIOUS CHAPTERS, we introduced the terms molecule, element, com- pound, and chemical change. In Chapter 1, you learned that chemical changes result in the transformation of one or more substances into one or more new substances. The processes involved in such changes are called Chemical Reactions. In this chapter, you will learn to write and read chemical equations that represent chemical reac- tions, to classify reactions, and to do calculations based on the application of the mole concept to chemical equations. 5.1 Chemical Equations Learning Objective 1 Identify the reactants and products in written reaction equations, and balance the equations by inspection. A simple chemical reaction between elemental hydrogen and oxygen has been used to power the engines of a number of spacecraft, including the space shuttle, which was oper- ated by the United States from 1981 to 2011 (see Figure 5.1). The products are water and much heat. For the moment, we will focus only on the substances involved; we will deal with the heat later.
eBook - PDFPhysical Chemistry
Understanding our Chemical World
- Paul M. S. Monk(Author)
- 2005(Publication Date)
- Wiley(Publisher)
A reaction can be thought of as a multi-step process: first the reactants approach and then they collide. Only after touching do they react. One of the more useful definitions 410 CHEMICAL KINETICS of reaction is ‘a rearrangement of bonds’. We are saying that, as a good generalization, the atomic nuclei remain stationary during the reaction while the electrons move. This idea is important, since it is the electrons that act as the ‘glue’ between the nuclei. Such movement occurs in such a way that the bonds between the atoms are different in the product than in the reactant. This simple yet profound notion, that atomic nuclei are stationary The Franck–Condon principle states that atomic nuclei are sta- tionary during a reac- tion, with only elec- trons moving – see p. 451. during the reaction and that only electrons have time to move, is called the Franck–Condon principle. We shall see its important consequences later, in Chapter 9. We now move on slightly, conceptually. Consider a single pair of reactant molecules combining to form a product. As electrons rearrange as the reaction commences, we pass smoothly from a structure that is purely reactant to one of pure product. The tran- sition from one to the other is seamless; see Figure 8.23. There will soon come a point where some bonds are almost broken and others almost formed. We have neither reactant nor product: it is a hybrid, being a mixture of both reactant and product. It is extremely unstable, and hence of extremely high energy (i.e. with respect to initial reactants or the eventual products). We call it the transition-state complex, and often give it the initials TS. To a first approximation, the character of the complex is predominantly reactant before the TS is formed, and predominantly product afterwards. The transition-state complex TS is only ever formed in minute concentrations and for a mere fraction of a second, e.g.
eBook - PDFStantec's Water Treatment
Principles and Design
- John C. Crittenden, R. Rhodes Trussell, David W. Hand, Kerry J. Howe, George Tchobanoglous(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
Intermediate products are formed during each step of a reaction leading up to the final products. An understanding of the mechanisms of a reaction may be used to improve the design and operation of water treatment processes. Reaction Mechanisms 232 5 Principles of Chemical Reactions ELEMENTARY REACTIONS Reaction mechanisms involving an individual reaction step are known as elementary reactions. Elementary reactions are used to describe what is happen- ing on a molecular scale, such as the collision of two reactants. For example, the decomposition of ozone (in organic-free, distilled water) has been described by the following four-step process (McCarthy and Smith, 1974): O H O HO OH 3 2 3 + → + + − (5-15) HO OH HO 3 2 2 + − + → (5-16) O HO HO O 3 2 2 2 + → •+ (5-17) HO HO H O O •+ → + 2 2 2 (5-18) In this series of elementary reactions, ozone reacts with water to form, among other compounds, HO• (hydroxyl radical) and HO 2 (superoxide), which are very reactive and sometimes used for the destruction of organic compounds. OVERALL REACTIONS A series of elementary reactions may be combined to yield an overall reaction. The overall reaction is determined by summing the elementary reactions and canceling out the compounds that occur on both sides of the reaction. For the elementary reactions shown in Eqs. 5-15 to 5-18, the over- all reaction may be written as 2O O 3 2 3 → (5-19) The specific reaction mechanism and intermediate products that are formed cannot be determined from the overall reaction sequence. In many cases the elementary reaction mechanisms are not known and empirical expressions must be developed to describe the reaction kinetics. Reaction Catalysis A catalyst speeds up a chemical reaction, but it is neither consumed nor produced by the reaction. For a reaction between two molecules to occur, the molecules must collide with the proper orientation. However, mole- cules have a tendency to move in ways that make the proper orientation less likely.
eBook - PDF- Leo J. Malone, Theodore O. Dolter(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
Much of the chemistry that occurs in our bodies is a result of the interaction of these compounds circulating in our blood- stream. So it seems appropriate to take a deeper look at the particular chemistry that occurs in aqueous solution. In Part A, we will introduce the chemical equation, how it is balanced, and three simple types of reactions. Types of re- actions are extended in Part B to include the many important reactions that occur in water. 180 CHAPTER 6 Chemical Reactions 6-1 Chemical Equations LOOKING AHEAD! The main rocket thruster of the space shuttle uses a simple but powerful chemical reaction. Hydrogen combines with oxygen to form water and a lot of heat energy. The way Chemical Reactions such as this are symbolized is the topic of this section. n 6-1.1 Constructing an Equation A chemical change can be illustrated symbolically by a chemical equation. A chemi- cal equation is the representation of a chemical reaction using the symbols of elements and the formulas of compounds. In the following discussion, we will focus on the matter that undergoes a change in the reaction. In Chapter 7, we will include the heat energy involved. Let’s start with a simple and fundamental reaction. We will build the chemical equation one step at a time that represents the reaction between hydrogen and oxygen to form water. This reaction powers the space shuttle. First, let’s represent with symbols the reaction of hydrogen combining with oxygen to form water. H + O ¡ H 2 O In a chemical equation, the original reacting species are shown to the left of the arrow and are called the reactants. The species formed as a result of the reaction are to the right of the arrow and are called the products. In this format, note that the phrase combines with (or reacts with) is represented by a plus sign (+). When there is more than one reactant or product, the symbols or formulas on each side of the equation are separated by a +.
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