Chemistry
Redox
Redox, short for reduction-oxidation, is a chemical reaction in which one substance transfers electrons to another. The substance that loses electrons is oxidized, while the one that gains electrons is reduced. Redox reactions are crucial in various chemical processes, including energy production, corrosion, and metabolism.
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eBook - PDF- Geoffrey M. Bowers, Ruth A. Bowers(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
61 chapter three Oxidation and reduction Cars are subject to (or take advantage of) oxidation/reduction (Redox) reactions—reactions where electrons are transferred between chemical species—every day. Several examples of important Redox reactions in cars include the combustion process in fossil fuel-burning engines, the electrochemistry involved in batteries and fuel cells, and the corrosion of metal car components. Because Redox reactions always involve a trans-fer of electrons, Redox chemistry may be used to generate a current, as in a battery, or be a relatively unnoticed aspect of a chemical reaction, as it often is in combustion or corrosion processes. Redox chemistry is also essential to metal plating and corrosion protection in vehicles. In this chapter, we will focus on understanding the details of these automotive applications of Redox chemistry. 3.1 A second look at combustion Chemistry Concepts : oxidation numbers, Redox terminology, activity series Expected Learning Outcomes : • Explain basic Redox terminology • Identify what is being oxidized and reduced in a combustion reaction In every Redox process, some element or chemical component gains electrons from another element or chemical component in the system. The species that loses electrons is said to be oxidized and the species that gains electrons reduced , and a Redox reaction always involves both oxidation and reduction. The origin of these terms relates to the chemical concept of oxidation numbers, which is a numerical system to track the flow of electrons in a chemical reaction, assuming that any electron trans-fer is complete. In other words, partial charges are not allowed. In most cases, the oxidation number of an ion is identical to its ideal charge in a particular substance, though the transition metals and many nonmet-als often have several possible oxidation states at most temperatures and pressures.
eBook - ePub- Clyde Frank(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Chapter TenOxidation–Reduction Equilibria
Publisher Summary
An oxidation-reduction reaction (Redox) is one in which the reactants undergo changes in the oxidation state. The gain of electrons is a reduction process, while oxidation is the loss of electrons. Both processes occur in a Redox reaction. Reduction does not take place in the absence of oxidation or vice versa. The total number of electrons lost is equal to the total number of electrons gained. The substance that decreases in the oxidation state is the oxidizing agent, while the substance that increases in the oxidation state is the reducing agent. An oxidizing agent causes another substance to be oxidized, while it itself is reduced. In contrast, the reducing agent causes another substance to be reduced, while it itself is oxidized. This chapter discusses the arrangement of oxidizing agents and their reduced forms according to their ability to gain and lose electrons. The chapter also illustrates an arrangement of a selected group of half-reactions, which is called the Table of Standard Reduction Potentials.DEFINITIONS
An oxidation–reduction reaction (Redox) is one in which the reactants undergo changes in oxidation state. In reaction (10-1),(10-1)which is also a suitable reaction for the determination of iron, cerium changes its oxidation state from 4+ to 3+, a gain of one electron, while iron changes from 2+ to 3+, a loss of one electron.A gain of electrons is a reduction process, while oxidation is a loss of electrons. In a Redox reaction both processes must occur. Reduction cannot take place in the absence of oxidation or vice versa. In addition, the total number of electrons lost must equal the total number of electrons gained.The substance that decreases in oxidation state is the oxidizing agent; the substance that increases in oxidation state is the reducing agent. An oxidizing agent causes another substance to be oxidized, while it itself is reduced. In contrast the reducing agent causes another substance to be reduced, while it itself is oxidized.
eBook - PDF- Ramesh Chandra, Snigdha Singh, Aarushi Singh(Authors)
- 2020(Publication Date)
- Arcler Press(Publisher)
Oxidation and Reduction CHAPTER 6 CONTENTS 6.1. Introduction .................................................................................... 176 6.2. The Concepts of Oxidation-Reduction ............................................ 177 6.3. Oxidation Reactions as a Loss of Electrons ...................................... 182 6.4. Electrolysis ...................................................................................... 184 6.5. The Concept of Oxidation Number ................................................. 186 6.6. Redox Reactions ............................................................................. 189 6.7. Types of Redox Reactions ................................................................ 191 6.8. Voltaic Cells .................................................................................... 196 6.9. Balancing of Redox Reactions ......................................................... 199 6.10. Location of Oxidants And Reductants In The Periodic Table .......... 201 6.11. Conclusion ................................................................................... 202 References ............................................................................................. 203 Organic Synthesis and Organic Reagents 176 In the chemical reactions, electrons are transferred from atom-to-atom. Oxidation-reduction reactions are commonly known as Redox reactions. Redox reaction is a chemical reaction in which the oxidation number changes by change gaining or losing an electron. This chapter gives the overview of the concepts of oxidation-reduction reaction. In the middle of the chapter, the concept of electrolysis and oxidation number is explained. This also provides insights about the different types of Redox reactions and the functioning of voltaic cell or dry cell. At the end of the chapter, the methods of balancing of Redox reactions and the location of oxidants and reductants are mentioned.
eBook - ePubChemistry
With Inorganic Qualitative Analysis
- Therald Moeller(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
19OXIDATION AND REDUCTION
Publisher Summary
This chapter explores the meaning of the terms “oxidation” and “reduction”. It presents the concept of electrochemistry to make clear the relationships among Redox reactions and what happens in electrochemical cells. The chapter describes the balancing of Redox equations. It presents the understanding and using of standard reduction potentials. The chapter discusses Nernst equation and explains the determination of equilibrium constants from standard reduction potentials. An oxidation-reduction reaction can be thought of as the sum of two half reactions. Each ion-electron equation includes both the oxidized form and the reduced form of the same species. Therefore, a complete Redox equation contains at least two oxidants, the electron acceptors and two reductants, the electron donors.In this chapter the meaning of the terms “oxidation” and “reduction” is explored, and just enough electrochemistry is presented to make clear the relationships between Redox reactions and what happens in electrochemical cells. (The electrochemical cells themselves are discussed in Chapter 24 .) The main additional topics covered are balancing Redox equations, understanding and using standard reduction potentials, and the Nernst equation and the determination of equilibrium constants from standard reduction potentials.T“Oxidation” and “reduction” are other words that have undergone changes in meaning. Earlierhe English language, like most others, is constantly changing. Words go out of fashion and disappear, new words are coined as new ideas and materials develop, and, most importantly, well-established words gradually assume new meanings. Consider, for example, the word “tremendous.” It was adapted into our language from a Latin word which meant “to cause to tremble”; that is, “awesome,” “dreadful,” “fearful.” Because we imagine awful and dreadful things to be very large, the word has come to mean “large.”
eBook - PDFChemistry in Focus
A Molecular View of Our World
- Nivaldo Tro(Author)
- 2018(Publication Date)
- Cengage Learning EMEA(Publisher)
Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Chapter 14 Oxidation and Reduction 360 Redox reactions are responsible for a number of common processes. The burning of hydrocarbons is a Redox reaction in which hydrocarbons are oxidized. Respiration is a Redox reaction in which our bodies oxidize sugars for energy. The refining of iron is a Redox reaction in which iron ores are reduced to extract their iron content, only to oxidize again—in spite of our efforts to prevent it. Paints, metals, and some plastics lose their brilliance over time due to oxidation. Some theories about aging hypothesize that oxidation is the cause. The rusting that occurs in ordinary iron, transforming a shiny new car into an old wreck, may be the same process that changes us from youth to old age. 14.2 Oxidation and Reduction: Some Definitions We have already encountered Redox reactions in this book. Combustion reactions, such as those used for heat or energy production, are actually Redox reactions. For example, the burning of coal is a Redox reaction: C 1 O 2 h CO 2 The combustion of natural gas is a Redox reaction: CH 4 1 2O 2 h CO 2 1 2H 2 O Other Redox reactions include the rusting of iron: 4Fe 1 3O 2 h 2Fe 2 O 3 and the sometimes explosive reaction between hydrogen and oxygen to form water: 2H 2 1 O 2 h 2H 2 O In each of these reactions, a substance reacts with oxygen: In the first reaction it is carbon, in the second reaction it is methane, in the third reaction it is iron, and in the fourth reaction it is hydrogen. Each of these substances reacts with oxygen and becomes oxidized. One definition of oxidation is simply the gaining of oxygen . If we were to reverse the arrows in these reactions, the elements named would all lose oxygen; they would be reduced.
eBook - PDF- Morris Hein, Susan Arena, Cary Willard(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
T he variety of oxidation–reduction reactions that affect us every day is amazing. Our society runs on batteries—in our calculators, laptop computers, cars, toys, radios, televisions, and more. The electric car in the photo is powered by an electric motor and lithium- ion batteries. The batteries are recharged by plugging the car into a household circuit. Oxidation– reduction reactions provide the energy in the batteries to drive the electric motor. We paint iron railings and galvanize nails to combat corrosion. We electroplate jewelry and computer chips with very thin coatings of gold or silver. We bleach our clothes using chemical reactions that involve electron transfer. We test for glucose in urine or alcohol in the breath with reactions that show vivid color changes. Plants turn energy into chemical compounds through a series of reactions called pho- tosynthesis. These reactions all involve the transfer of electrons between substances in a chemical process called oxidation–reduction. Igor Karasi/Shutterstock Oxidation– Reduction 17 C H A P T E R O U T L I N E 17.1 Oxidation Number 17.2 Balancing Oxidation–Reduction Equations 17.3 Balancing Ionic Redox Equations 17.4 Activity Series of Metals 17.5 Electrolytic and Voltaic Cells 398 CHAPTER 17 • Oxidation–Reduction 17.1 Oxidation Number Assign oxidation numbers to the atoms in a compound. The oxidation number of an atom (sometimes called its oxidation state) represents the num- ber of electrons lost, gained, or unequally shared by an atom. Oxidation numbers can be zero, positive, or negative. An oxidation number of zero means the atom has the same num- ber of electrons assigned to it as there are in the free neutral atom. A positive oxidation num- ber means the atom has fewer electrons assigned to it than in the neutral atom, and a negative oxidation number means the atom has more electrons assigned to it than in the neutral atom.
eBook - ePubIntroduction to Geochemistry
Principles and Applications
- Kula C. Misra(Author)
- 2012(Publication Date)
- Wiley-Blackwell(Publisher)
4 ). Oxidation–reduction reactions are important in all geologic processes: magmatic, diagenetic, metamorphic, chemical weathering (e.g., the familiar reddish-yellow rust on iron garden tools), and formation of mineral deposits. In the realm of industrial applications, oxidation–reduction reactions are the basis of electrochemistry (chemical changes produced by an electric current and the production of electricity by chemical reactions), recovery of metals from many types of ores and wastes, and treatment of municipal sewage and industrial effluents.8.1 Definitions
Reactions resulting from addition of oxygen (e.g., 2Ni + O2 = 2NiO) evidently represent oxidation. However, a reaction does not have to involve oxygen to qualify as an oxidation or a reduction reaction.Oxidation is defined as a reaction involving the loss of one or more electrons and reduction as a reaction involving the gain of one or more electrons.Thus, oxidation involves an increase in oxidation state , and reduction a decrease in oxidation state. For the purpose of illustration, let us consider the oxidation of magnetite (Fe2 + O. ) to hematite in the presence of water. Following the convention used by Garrels and Christ (1965, p. 132) and subsequently by many other authors (e.g., Krauskopf and Bird, 1995; Faure, 1998; McSween et al
- Olcay Tunay, Isik Kabdasli, Idil Arslan-Alaton, Tugba Olmez-Hanci(Authors)
- 2010(Publication Date)
- IWA Publishing(Publisher)
© 2010 IWA Publishing. Chemical Oxidation Applications for Industrial Wastewaters . By Olcay Tünay, Işık Kabdaşlı, Idil Arslan-Alaton and Tuğba Ölmez-Hancı . ISBN: 9781843393078. Published by IWA Publishing, London, UK. Chapter 1 Introduction to Redox reactions 1.1 INTRODUCTION 1.1.1 Redox processes Chemical oxidation is a process in which the oxidation state of an atom is increased. The atom being oxidised may be in the elemental form or in a substance like a molecule or ion. The term “oxidised” is also used for the substance containing the oxidised atom. If the oxidation takes place within biological processes the terms biological or biologically-mediated oxidation are used. Chemical reduction is the process by which the oxidation state, the valence, of an atom is reduced. Every oxidation reaction is accompanied by a reduction reaction and these reactions are termed Redox reactions. For inorganic Redox reactions, oxidation and reduction are brought about by electron transfer. Oxidation is the loss of electrons and reduction is the gain of electrons by an atom. In the below example: 2 0 2 S + I 2I + S − − → (1.1) Sulphide ion is oxidised to elemental sulphur by losing two electrons, while elemental iodine is reduced to iodide ion by gaining two electrons. In the organic 2 Chemical Oxidation Applications for Industrial Wastewaters reactions, the mechanism is more complex. An organic reaction oxidation is carried out by replacement of one of the electrons making up the covalent bond between two atoms, by changing one of the atoms in a way for reversing the order of electronegativities of the atoms. If atoms A and B are tied up with a covalent bond and atom A is more electronegative than atom B, replacement of atom B by atom C which is more electronegative than atom A, through breaking the A-B bond and formation of an A-C bond, results in the oxidation of atom A.
eBook - ePub- Daniel G. Strawn, Hinrich L. Bohn, George A. O'Connor(Authors)
- 2019(Publication Date)
- Wiley-Blackwell(Publisher)
5 Redox REACTIONS IN SOILS5.1 Introduction
In reduction and oxidation reactions, atoms exchange electrons causing changes in oxidation states and chemical species, and thus dramatically change the behavior of chemicals in soils. Redox reactions can be abiotic or biotically driven. In most natural systems, biological reactions have the greatest influence on Redox processes. Redox reactions are fundamental to biogeochemical processes in soils because they influence pedogenesis and change mobility and bioavailability of nutrients and contaminants.Table 5.1shows some of the most common elements involved in Redox processes in soils, and their oxidation states.Oxidation is the loss or donation of electrons by an element. Reduction is the gain or acceptance of electrons. For example, the reduction reaction of Fe3+ to Fe2+ , which is an Fe3+ –Fe2+ couple, is(5.1)where e– is a free electron. The reaction inEq. 5.1is a half‐reaction because it does not show where the electron is coming from, and thus describes only half of a complete reaction. Although half‐reactions imply that free electrons exist, the free electron is a theoretical concept that does not occur in nature; the electron is always associated with an atom and directly transferred between ions or molecules. Thus, reduction of one substance requires oxidation of another.An example of an oxidation half‐reaction that provides electrons is oxidation of sulfide to elemental sulfur (S2− –S0 couple):(5.2)This half‐reaction produces two electrons that must be donated to another element in a reducing half‐reaction, which is not shown.Reactions inEq. 5.1andEq. 5.2
- Anju Goyal, Harish Kumar, Anju Goyal, Harish Kumar(Authors)
- 2022(Publication Date)
- Bentham Science Publishers(Publisher)
2 ].Principle and Theory
The basic principle involved in Redox titration is the oxidation-reduction reactions, in which electron transfer from one reactant to another reactant takes place. Oxidation involved loss of electron and reduction involved gain of electron. These must happen at the same time; when a substance loses electrons, then there must be some other substance to accept those electrons (Fig.Fig. (1)) Showing mechanism of Redox titration.).1In the diagram provided above, it is illustrated that an electron was removed from reactant A, and the reactant got oxidized. Likewise, reactant B was handed an electron and thus got reduced. The process of loss of electrons and increase in the oxidation state of a given reactant is called oxidation whereas, gain of electrons and decrease in the oxidation state of a reactant is called reduction. Oxidation state or oxidation number is the total number of electrons either loose or gain by an atom in order to make a chemical bond with another atom. For example, Fe3+ has oxidation number 3, which means it has 3 electrons to make a chemical bond. In the Redox reactions, the compounds that accept electrons and endure reduction are called oxidizing agents. The electron donating species that surrender electrons, termed as reducing agents, go through oxidation. From these details, it can be demonstrated that Redox reactions can be fragmented into two half, reduction half reaction and the oxidation half reaction.Examples: The assay of FeSO4 using ceric sulphate. The equation involved in the reaction is:Fe2+ + Ce4+ → Fe3+ + Ce3+2FeSO4 + 2Ce(SO4 )2 → Fe(SO4 )3 +Ce2 (SO4 )3This equation can be fragmented into two half, one half represented by ferrous ion which lose electrons and the other half shown by cerric ion which gains electrons. Oxidation means loss of electron, removal of hydrogen and addition of oxygen.
eBook - PDFThermodynamics of Natural Systems
Theory and Applications in Geochemistry and Environmental Science
- Greg Anderson(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
Without such electron transfers, these and many other reactions, including many necessary to life processes, could not proceed. 11.3 The Role of Oxygen ............................................................................... Both of our examples involve oxygen, which is the most common oxidizing agent in natural systems. In the presence of oxygen, many elements are oxidized (lose electrons, gain in valence), while oxygen is reduced. You need only think of rusty nails, green staining on copper objects, and burning logs to realize the truth of this. The process of oxidation obviously takes its name from the fact that oxygen is the premier oxidizing agent, but it is actually defined in terms of electron loss, or increase in valence. In other words, the electrons need not come from or go to oxygen; many Redox reactions take place without oxygen. Consider, for example, what happens when you put a piece of iron in a solution of copper sulfate ( Figure 11.1 ). After a while you see the characteristic color of metallic Figure 11.1 An iron nail in a solution of copper sulfate. 259 11.4 A Simple Electrolytic Cell copper forming on the surface of the iron, and the iron gradually crumbles and eventually disappears. Metallic copper precipitates, and iron dissolves. The reaction is essentially Cu 2 + + Fe → Cu + Fe 2 + (11.1) We need not include the sulfate, because it is not involved in this process – being negatively charged, the SO 2 − 4 ions provide an overall charge balance in the solution. In this example, copper is reduced and iron is oxidized, without the aid of oxygen.
eBook - PDF- Leo J. Malone, Theodore O. Dolter(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
pp. 480−481 14-1.2 An electron exchange reaction is known as an oxidation-reduction, or simply Redox, reaction. p. 481 14-1.2 The species reduced is known as the oxidizing agent; the species oxidized is known as the reducing agent. p. 481 14-1.3 Oxidation states (or oxidation numbers) are used to identify the elements that change in Redox reactions. p. 482 14-2 The oxidation state or bridge method balances equations by focusing on the oxida- tion state changes. p. 486 14-3 The ion-electron method is used to balance half-reactions separately before adding to the total reaction. p. 489 Oxidizing and Reducing Agents reactant oxidized oxidizing agent reactant reduced reducing agent by the 88888n by the 88888n is the 8888888888n is the 8888888888n Balancing Redox Reactions in Aqueous Solution Unbalanced core reaction: X + AO - ¡XO 2- + A Acidic solution Separate into two half-reactions X ¡ XO 2 - AO - ¡ A Add H 2 O 2H 2 O + X ¡ XO 2 - AO - ¡ A + H 2 O Add H + 2H 2 O + X ¡ XO 2 - + 4H + 2H + + AO - ¡ A + H 2 O Add e - 2H 2 O + X ¡ XO 2 - + 4H + + 3e - e - + 2H + + AO - ¡ A + H 2 O Balance electron exchange 2H 2 O + X ¡ XO 2 - + 4H + + 3e - 3e - + 6H + + 3AO - ¡ 3A + 3H 2 O Add two reactions and simplify 2H + + X + 3AO - ¡XO 2 - + 3A + H 2 O To change to a basic solution Add OH - (on both sides) for each H + (2H + + 2OH - ) + X + 3AO - ¡ XO 2 - + 3A + H 2 O+ 2OH - Combine H + and OH - to make H 2 O and simplify H 2 O + X + 3AO - ¡ XO 2 - + 3A + 2OH - SUMMARY CHART EXERCISE 14-3(b) LEVEL 3: When elemental tin is placed in a nitric acid solution, a spontaneous Redox reaction occurs, producing solid tin(IV) oxide and nitrogen dioxide gas. Write the equation illustrating this reaction and balance the equation by the ion-electron method. (Water is also a product.) For additional practice, work chapter problems 14-18, 14-20, 14-22, and 14-24.
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