Unit 2 Redox and Electrochemistry Notes
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Redox Models in Chemistry
Redox models in chemistry A depiction of the conceptions held by secondary school students of redox reactions Lise-Lotte Österlund Department of Chemistry 901 87 Umeå Umeå 2010 Copyright©Lise-Lotte Österlund ISBN: 978-91-7459-053-1 ISSN: 1652-5051 Cover picture: Photographer, Lise-Lotte Österlund Printed by: VMC, KBC, Umeå University Umeå, Sweden 2010 T0 my family Abstract According to previous research, students show difficulties in learning redox reactions. By the historical development different redox models exist to explain redox reactions, the oxygen model, the hydrogen model, the electron model and the oxidation number model. This thesis reports about three studies concerning conceptions held by secondary school students of redox reactions. A textbook analysis is also included in the thesis. The first study was an investigation of the students’ use of redox models in inorganic contexts, their use of the activity series of metals, and the students’ ability to transfer redox knowledge. Then the students’ work with an open- ended biochemical task, where the students had access of the textbook was studied. The students talk about redox reactions, the questions raised by the students, what resources used to answer the questions and what kind of talk developed were investigated. A textbook analysis based on chemistry books from Sweden and one book from England was performed. The redox models used as well as the dealing with redox related learning difficulties was studied. Finally, the students’ conceptions about redox in inorganic, organic and biochemistry after completed chemistry courses were studied. The results show that the students were able to use the electron model as a tool to explain inorganic redox reactions and the mutuality of oxidation and reduction was fundamental. -
Promotion Effects and Mechanism of Alkali Metals and Alkaline Earth
Subscriber access provided by RES CENTER OF ECO ENVIR SCI Article Promotion Effects and Mechanism of Alkali Metals and Alkaline Earth Metals on Cobalt#Cerium Composite Oxide Catalysts for N2O Decomposition Li Xue, Hong He, Chang Liu, Changbin Zhang, and Bo Zhang Environ. Sci. Technol., 2009, 43 (3), 890-895 • DOI: 10.1021/es801867y • Publication Date (Web): 05 January 2009 Downloaded from http://pubs.acs.org on January 31, 2009 More About This Article Additional resources and features associated with this article are available within the HTML version: • Supporting Information • Access to high resolution figures • Links to articles and content related to this article • Copyright permission to reproduce figures and/or text from this article Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Environ. Sci. Technol. 2009, 43, 890–895 Promotion Effects and Mechanism such as Fe-ZSM-5 are more active in the selective catalytic reduction (SCR) of N2O by hydrocarbons than in the - ° of Alkali Metals and Alkaline Earth decomposition of N2O in a temperature range of 300 400 C (3). In recent years, it has been found that various mixed Metals on Cobalt-Cerium oxide catalysts, such as calcined hydrotalcite and spinel oxide, showed relatively high activities. Composite Oxide Catalysts for N2O One of the most active oxide catalysts is a mixed oxide containing cobalt spinel. Calcined hydrotalcites containing Decomposition cobalt, such as Co-Al-HT (9-12) and Co-Rh-Al-HT (9, 11), have been reported to be very efficient for the decomposition 2+ LI XUE, HONG HE,* CHANG LIU, of N2O. -
Prebiological Evolution and the Metabolic Origins of Life
Prebiological Evolution and the Andrew J. Pratt* Metabolic Origins of Life University of Canterbury Keywords Abiogenesis, origin of life, metabolism, hydrothermal, iron Abstract The chemoton model of cells posits three subsystems: metabolism, compartmentalization, and information. A specific model for the prebiological evolution of a reproducing system with rudimentary versions of these three interdependent subsystems is presented. This is based on the initial emergence and reproduction of autocatalytic networks in hydrothermal microcompartments containing iron sulfide. The driving force for life was catalysis of the dissipation of the intrinsic redox gradient of the planet. The codependence of life on iron and phosphate provides chemical constraints on the ordering of prebiological evolution. The initial protometabolism was based on positive feedback loops associated with in situ carbon fixation in which the initial protometabolites modified the catalytic capacity and mobility of metal-based catalysts, especially iron-sulfur centers. A number of selection mechanisms, including catalytic efficiency and specificity, hydrolytic stability, and selective solubilization, are proposed as key determinants for autocatalytic reproduction exploited in protometabolic evolution. This evolutionary process led from autocatalytic networks within preexisting compartments to discrete, reproducing, mobile vesicular protocells with the capacity to use soluble sugar phosphates and hence the opportunity to develop nucleic acids. Fidelity of information transfer in the reproduction of these increasingly complex autocatalytic networks is a key selection pressure in prebiological evolution that eventually leads to the selection of nucleic acids as a digital information subsystem and hence the emergence of fully functional chemotons capable of Darwinian evolution. 1 Introduction: Chemoton Subsystems and Evolutionary Pathways Living cells are autocatalytic entities that harness redox energy via the selective catalysis of biochemical transformations. -
How Do We Learn Electrochemistry? by Jeffrey W
redcat_ad_IF_Sp2012_1.pdf 1 4/11/2012 1:36:17 PM research • news • events • resources | search • explore • connect • share • discover How Do We Learn Electrochemistry? by Jeffrey W. Fergus he importance of electrochemistry is undeniable—we on education. The fall 2006 issue was devoted to education literally cannot live without electrochemistry for proper and included articles discussing general needs for education in Tcell function and transmission of signals through the electrochemistry as well as some examples of approaches, and nervous system. Electrochemistry is also vital in a wide range even specific laboratory activities, to enhance electrochemical of important technological applications. For example, batteries education. More recently, in the summer 2010 issue, the ECS are important not only in storing energy for mobile devices Industrial Electrochemistry and Electrochemical Engineering and vehicles, but also for load leveling to enable the use of Division provided an additional evaluation of needs and some renewable energy conversion technologies. Electrochemistry activities for introducing electrochemistry into courses. The is involved in the production of materials by electrorefining current issue complements those earlier issues and provides or electrodeposition as well as the destruction of materials by insights on the status and needs in electrochemical education. TM corrosion. In spite of its ubiquity there are very few formal The first article provides a general backdrop on the state educational degree programs in electrochemistry. of higher education. Marye Ann Fox discusses the financial If electrochemistry is ubiquitous, but formal educational challenges being faced by academic institutions and how these programs are rare, how do the scientists and engineers working on challenges have an impact on the design and implementation of electrochemical products and processes learn the electrochemistry educational programs. -
The Relationship of PSAT/NMSQT Scores and AP Examination Grades
Research Notes Office of Research and Development RN-02, November 1997 The Relationship of PSAT/NMSQT Scores and AP® Examination Grades he PSAT/NMSQT, which measures devel- Recent analyses have shown that student per- oped verbal and quantitative reasoning, as formance on the PSAT/NMSQT can be useful in Twell as writing skills generally associated identifying additional students who may be suc- with academic achievement in college, is adminis- cessful in AP courses. PSAT/NMSQT scores can tered each October to nearly two million students, identify students who may not have been initially the vast majority of whom are high school juniors considered for an AP course through teacher or and sophomores. PSAT/NMSQT information has self-nomination or other local procedures. For been used by high school counselors to assist in many AP courses, students with moderate scores advising students in college planning, high school on the PSAT/NMSQT have a high probability of suc- course selection, and for scholarship awards. In- cess on the examinations. For example, a majority formation from the PSAT/NMSQT can also be very of students with PSAT/NMSQT verbal scores of useful for high schools in identifying additional 46–50 received grades of 3 or above on nearly all of students who may be successful in Advanced the 29 AP Examinations studied, while over one- Placement courses, and assisting schools in deter- third of students with scores of 41–45 achieved mining whether to offer additional Advanced grades of 3 or above on five AP Examinations. Placement courses. There are substantial variations across AP subjects that must be considered. -
Electrochemical Real-Time Mass Spectrometry: a Novel Tool for Time-Resolved Characterization of the Products of Electrochemical Reactions
Electrochemical real-time mass spectrometry: A novel tool for time-resolved characterization of the products of electrochemical reactions Elektrochemische Realzeit-Massenspektrometrie: Eine neuartige Methode zur zeitaufgelösten Charakterisierung der Produkte elektrochemischer Reaktionen Der Technischen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg zur Erlangung des Doktorgrades Dr.-Ingenieur vorgelegt von Peyman Khanipour Mehrin aus Shiraz, Iran Als Dissertation genehmigt von der Technischen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg Tag der mündlichen Prüfung: 17.11.2020 Vorsitzender des Promotionsorgans: Prof. Dr.-Ing. habil. Andreas Paul Fröba Gutachter: Prof. Dr. Karl J.J. Mayrhofer Prof. Dr. Frank-Michael Matysik I Acknowledgements This study is done in the electrosynthesis team of the electrocatalysis unit at Helmholtz- Institut Erlangen-Nürnberg (HI ERN) with the financial support of Forschungszentrum Jülich. I would like to express my deep gratitude to Prof. Dr. Karl J. J. Mayrhofer for accepting me as a Ph.D. student and also for all his encouragement, supports, and freedoms during my study. I’m grateful to Prof. Dr. Frank-Michael Matysik for kindly accepting to act as a second reviewer and also for the time he has invested in reading this thesis. This piece of work is enabled by collaboration with scientists from different expertise. I would like to express my appreciation to Dr. Sandra Haschke from FAU for providing shape-controlled high surface area platinum electrodes which I used for performing oxidation of primary alcohols and also the characterization of the provided material SEM, EDX, and XRD. Mr. Mario Löffler from HI ERN for obtaining the XPS data and his remarkable knowledge with the interpretation of the spectra on copper-based electrodes for the CO 2 electroreduction reaction. -
Gas-Phase Electrochemistry: Measuring Absolute Potentials and Investigating Ion and Electron Hydration*
Pure Appl. Chem., Vol. 83, No. 12, pp. 2129–2151, 2011. doi:10.1351/PAC-CON-11-08-15 © 2011 IUPAC, Publication date (Web): 7 October 2011 Gas-phase electrochemistry: Measuring absolute potentials and investigating ion and electron hydration* William A. Donald1,‡ and Evan R. Williams2 1School of Chemistry, Bio21 Institute of Molecular Science and Biotechnology, and ARC Centre of Excellence for Free Radical Chemistry and Biotechnology, University of Melbourne, Melbourne, Victoria, Australia; 2Department of Chemistry, University of California, Berkeley, CA, USA Abstract: In solution, half-cell potentials and ion solvation energies (or enthalpies) are meas- ured relative to other values, thus establishing ladders of thermochemical values that are ref- erenced to the potential of the standard hydrogen electrode (SHE) and the proton hydration energy (or enthalpy), respectively, which are both arbitrarily assigned a value of 0. In this focused review article, we describe three routes for obtaining absolute solution-phase half- cell potentials using ion nanocalorimetry, in which the energy resulting from electron capture (EC) by large hydrated ions in the gas phase are obtained from the number of water mole- cules lost from the reduced precursor cluster, which was developed by the Williams group at the University of California, Berkeley. Recent ion nanocalorimetry methods for investigating ion and electron hydration and for obtaining the absolute hydration enthalpy of the electron are discussed. From these methods, an absolute electrochemical scale and ion solvation scale can be established from experimental measurements without any models. Keywords: absolute potentials; clusters; electrochemistry; electron capture dissociation; elec- tron transfer; gaseous state; hydrated ions; hydration; ion nanocalorimetry; solvation; thermo chemistry. -
Electrochemistry Cell Model
Electrochemistry Cell Model Dennis Dees and Kevin Gallagher Chemical Sciences and Engineering Division May 9-13, 2011 Vehicle Technologies Program Annual Merit Review and Peer Evaluation Meeting Washington, D.C. Project ID: ES031 This presentation does not contain any proprietary, confidential, or otherwise restricted information. Overview Timeline Barriers . Start: October 2008 . Development of a safe cost-effective PHEV . Finish: September 2014 battery with a 40 mile all electric range . ~43% Complete that meets or exceeds all performance goals – Interpreting complex cell electrochemical phenomena – Identification of cell degradation mechanisms Budget Partners (Collaborators) . Total project funding . Daniel Abraham, Argonne – 100% DOE . Sun-Ho Kang, Argonne . FY2010: $400K . Andrew Jansen, Argonne . FY2011: $400K . Wenquan Lu, Argonne . Kevin Gering, INL Vehicle Technologies Program 2 Objectives, Milestones, and Approach . The objective of this work is to correlate analytical diagnostic results with the electrochemical performance of advanced lithium-ion battery technologies for PHEV applications – Link experimental efforts through electrochemical modeling studies – Identify performance limitations and aging mechanisms . Milestones for this year: – Initiate development of AC impedance two phase model (completed) – Integrate SEI growth model into full cell model (completed) . Approach for electrochemical modeling activities is to build on earlier successful characterization and modeling studies in extending efforts to new PHEV technologies -
Chapter 20 Electrochemistry
Chapter 20 Electrochemistry Learning goals and key skills: Identify oxidation, reduction, oxidizing agent, and reducing agent in a chemical equation Complete and balance redox equations using the method of half-reactions. Sketch a voltaic cell and identify its cathode, anode, and the directions in which electrons and ions move. o Calculate standard emfs (cell potentials), E cell, from standard reduction potentials. Use reduction potentials to predict whether a redox reaction is spontaneous. o o Relate E cell to DG and equilibrium constants. Calculate emf under nonstandard conditions. Identify the components of common batteries. Describe the construction of a lithium-ion battery and explain how it works. Describe the construction of a fuel cell and explain how it generates electrical energy. Explain how corrosion occurs and how it is prevented by cathodic protection. Describe the reactions in electrolytic cells. Relate the amounts of products and reactants in redox reactions to electrical charge. Electrochemistry Electrochemistry is the study of the relationships between electricity and chemical reactions. • It includes the study of both spontaneous and nonspontaneous processes. 1 Redox reactions: assigning oxidation numbers Oxidation numbers help keep track of what species loses electrons and what species gains them. • An element is oxidized when the oxidation number increases • An element is reduced when the oxidation number decreases • an oxidizing agent causes another element to be oxidized • a reducing agent causes another element to be reduced. Assigning oxidation numbers (sect. 4.4) 1. Elemental form, each atom has ox. # = 0. Zn O2 O3 I2 S8 P4 2. Simple ions, = charge on ion. -1 for Cl-, +2 for Mg2+ 3. -
Physical and Analytical Electrochemistry: the Fundamental
Electrochemical Systems The simplest and traditional electrochemical process occurring at the boundary between an electronically conducting phase (the electrode) and an ionically conducting phase (the electrolyte solution), is the heterogeneous electro-transfer step between the electrode and the electroactive species of interest present in the solution. An example is the plating of nickel. Ni2+ + 2e- → Ni Physical and Analytical The interface is where the action occurs but connected to that central event are various processes that can Electrochemistry: occur in parallel or series. Figure 2 demonstrates a more complex interface; it represents a molecular scale snapshot The Fundamental Core of an interface that exists in a fuel cell with a solid polymer (capable of conducting H+) as an electrolyte. of Electrochemistry However, there is more to an electrochemical system than a single by Tom Zawodzinski, Shelley Minteer, interface. An entire circuit must be made and Gessie Brisard for measurable current to flow. This circuit consists of the electrochemical cell plus external wiring and circuitry The common event for all electrochemical processes is that (power sources, measuring devices, of electron transfer between chemical species; or between an etc). The cell consists of (at least) electrode and a chemical species situated in the vicinity of the two electrodes separated by (at least) one electrolyte solution. Figure 3 is electrode, usually a pure metal or an alloy. The location where a schematic of a simple circuit. Each the electron transfer reactions take place is of fundamental electrode has an interface with a importance in electrochemistry because it regulates the solution. Electrons flow in the external behavior of most electrochemical systems. -
Redox Potential Measurements M.J
Redox Potential Measurements M.J. Vepraskas NC State University December 2002 Redox potential is an electrical measurement that shows the tendency of a soil solution to transfer electrons to or from a reference electrode. From this measurement we can estimate whether the soil is aerobic, anaerobic, and whether chemical compounds such as Fe oxides or nitrate have been chemically reduced or are present in their oxidized forms. Making these measurements requires three basic pieces of equipment: 1. Platinum electrode 2. Voltmeter 3. Reference electrode The basic set-up is shown below: Voltmeter 456 mv Soil surface Reference Pt wire electrode Fig. 1. The Pt wire is buried into the soil to be in contact with the soil solution. The reference electrode must also be in contact with the soil solution. It has a ceramic tip, which can be placed in the soil, or the electrode can be placed in a salt bridge, which is itself placed in the soil. Wires from both the Pt electrode and reference electrode are connected to the voltmeter. Pt Electrodes Platinum electrodes consist of a small piece of platinum wire that is soldered or fused to wire made another metal. Platinum conducts electrons from the soil solution to the wire to which it is attached. Platinum is used because it is assumed to be an inert metal. This means it does not give up its own electrons (does not oxidize) to the wire or soil solution. Iron containing materials such as steel will oxidize themselves and send their own electrons to the voltmeter. As a result the voltage we measure will not result solely from electrons being transferred to or from the soil. -
Introduction to Chemistry
Introduction to Chemistry Author: Tracy Poulsen Digital Proofer Supported by CK-12 Foundation CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook Introduction to Chem... materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based Authored by Tracy Poulsen collaborative model termed the “FlexBook,” CK-12 intends to pioneer the generation and 8.5" x 11.0" (21.59 x 27.94 cm) distribution of high-quality educational content that will serve both as core text as well as provide Black & White on White paper an adaptive environment for learning. 250 pages ISBN-13: 9781478298601 Copyright © 2010, CK-12 Foundation, www.ck12.org ISBN-10: 147829860X Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made Please carefully review your Digital Proof download for formatting, available to Users in accordance with the Creative Commons Attribution/Non-Commercial/Share grammar, and design issues that may need to be corrected. Alike 3.0 Unported (CC-by-NC-SA) License (http://creativecommons.org/licenses/by-nc- sa/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), We recommend that you review your book three times, with each time focusing on a different aspect. which is incorporated herein by this reference. Specific details can be found at http://about.ck12.org/terms. Check the format, including headers, footers, page 1 numbers, spacing, table of contents, and index. 2 Review any images or graphics and captions if applicable.