PDF (Chapter 5
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Chemistry Grade Level 10 Units 1-15
COPPELL ISD SUBJECT YEAR AT A GLANCE GRADE HEMISTRY UNITS C LEVEL 1-15 10 Program Transfer Goals ● Ask questions, recognize and define problems, and propose solutions. ● Safely and ethically collect, analyze, and evaluate appropriate data. ● Utilize, create, and analyze models to understand the world. ● Make valid claims and informed decisions based on scientific evidence. ● Effectively communicate scientific reasoning to a target audience. PACING 1st 9 Weeks 2nd 9 Weeks 3rd 9 Weeks 4th 9 Weeks Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6 Unit Unit Unit Unit Unit Unit Unit Unit Unit 7 8 9 10 11 12 13 14 15 1.5 wks 2 wks 1.5 wks 2 wks 3 wks 5.5 wks 1.5 2 2.5 2 wks 2 2 2 wks 1.5 1.5 wks wks wks wks wks wks wks Assurances for a Guaranteed and Viable Curriculum Adherence to this scope and sequence affords every member of the learning community clarity on the knowledge and skills on which each learner should demonstrate proficiency. In order to deliver a guaranteed and viable curriculum, our team commits to and ensures the following understandings: Shared Accountability: Responding -
The Practice of Chemistry Education (Paper)
CHEMISTRY EDUCATION: THE PRACTICE OF CHEMISTRY EDUCATION RESEARCH AND PRACTICE (PAPER) 2004, Vol. 5, No. 1, pp. 69-87 Concept teaching and learning/ History and philosophy of science (HPS) Juan QUÍLEZ IES José Ballester, Departamento de Física y Química, Valencia (Spain) A HISTORICAL APPROACH TO THE DEVELOPMENT OF CHEMICAL EQUILIBRIUM THROUGH THE EVOLUTION OF THE AFFINITY CONCEPT: SOME EDUCATIONAL SUGGESTIONS Received 20 September 2003; revised 11 February 2004; in final form/accepted 20 February 2004 ABSTRACT: Three basic ideas should be considered when teaching and learning chemical equilibrium: incomplete reaction, reversibility and dynamics. In this study, we concentrate on how these three ideas have eventually defined the chemical equilibrium concept. To this end, we analyse the contexts of scientific inquiry that have allowed the growth of chemical equilibrium from the first ideas of chemical affinity. At the beginning of the 18th century, chemists began the construction of different affinity tables, based on the concept of elective affinities. Berthollet reworked this idea, considering that the amount of the substances involved in a reaction was a key factor accounting for the chemical forces. Guldberg and Waage attempted to measure those forces, formulating the first affinity mathematical equations. Finally, the first ideas providing a molecular interpretation of the macroscopic properties of equilibrium reactions were presented. The historical approach of the first key ideas may serve as a basis for an appropriate sequencing of -
Enzyme Activity and Assays Introductory Article
Enzyme Activity and Assays Introductory article Robert K Scopes, La Trobe University, Bundoora, Victoria, Australia Article Contents . Factors that Affect Enzymatic Analysis Enzyme activity refers to the general catalytic properties of an enzyme, and enzyme assays . Initial Rates and Steady State Turnover are standardized procedures for measuring the amounts of specific enzymes in a sample. Measurement of Enzyme Activity . Measurement of Protein Concentration Factors that Affect Enzymatic Analysis . Methods for Purifying Enzymes . Summary Enzyme activity is measured in vitro under conditions that often do not closely resemble those in vivo. The objective of measuring enzyme activity is normally to determine the exactly what the concentration is (some preparations of amount of enzyme present under defined conditions, so unusual substrates may be impure, or the exact amount that activity can be compared between one sample and present may not be known). This is because the rate another, and between one laboratory and another. The measured varies with substrate concentration more rapidly conditions chosen are usually at the optimum pH, as the substrate concentration decreases, as can be seen in ‘saturating’ substrate concentrations, and at a temperature Figure 1. In most cases an enzyme assay has already been that is convenient to control. In many cases the activity is established, and the substrate concentration, buffers and measured in the opposite direction to that of the enzyme’s other parameters used previously should be used again. natural function. Nevertheless, with a complete study of There are many enzymes which do not obey the simple the parameters that affect enzyme activity it should be Michaelis–Menten formula. -
Chapter 12 Lecture Notes
Chemical Kinetics “The study of speeds of reactions and the nanoscale pathways or rearrangements by which atoms and molecules are transformed to products” Chapter 13: Chemical Kinetics: Rates of Reactions © 2008 Brooks/Cole 1 © 2008 Brooks/Cole 2 Reaction Rate Reaction Rate Combustion of Fe(s) powder: © 2008 Brooks/Cole 3 © 2008 Brooks/Cole 4 Reaction Rate Reaction Rate + Change in [reactant] or [product] per unit time. Average rate of the Cv reaction can be calculated: Time, t [Cv+] Average rate + Cresol violet (Cv ; a dye) decomposes in NaOH(aq): (s) (mol / L) (mol L-1 s-1) 0.0 5.000 x 10-5 13.2 x 10-7 10.0 3.680 x 10-5 9.70 x 10-7 20.0 2.710 x 10-5 7.20 x 10-7 30.0 1.990 x 10-5 5.30 x 10-7 40.0 1.460 x 10-5 3.82 x 10-7 + - 50.0 1.078 x 10-5 Cv (aq) + OH (aq) → CvOH(aq) 2.85 x 10-7 60.0 0.793 x 10-5 -7 + + -5 1.82 x 10 change in concentration of Cv Δ [Cv ] 80.0 0.429 x 10 rate = = 0.99 x 10-7 elapsed time Δt 100.0 0.232 x 10-5 © 2008 Brooks/Cole 5 © 2008 Brooks/Cole 6 1 Reaction Rates and Stoichiometry Reaction Rates and Stoichiometry Cv+(aq) + OH-(aq) → CvOH(aq) For any general reaction: a A + b B c C + d D Stoichiometry: The overall rate of reaction is: Loss of 1 Cv+ → Gain of 1 CvOH Rate of Cv+ loss = Rate of CvOH gain 1 Δ[A] 1 Δ[B] 1 Δ[C] 1 Δ[D] Rate = − = − = + = + Another example: a Δt b Δt c Δt d Δt 2 N2O5(g) 4 NO2(g) + O2(g) Reactants decrease with time. -
Opportunities for Catalysis in the 21St Century
Opportunities for Catalysis in The 21st Century A Report from the Basic Energy Sciences Advisory Committee BASIC ENERGY SCIENCES ADVISORY COMMITTEE SUBPANEL WORKSHOP REPORT Opportunities for Catalysis in the 21st Century May 14-16, 2002 Workshop Chair Professor J. M. White University of Texas Writing Group Chair Professor John Bercaw California Institute of Technology This page is intentionally left blank. Contents Executive Summary........................................................................................... v A Grand Challenge....................................................................................................... v The Present Opportunity .............................................................................................. v The Importance of Catalysis Science to DOE.............................................................. vi A Recommendation for Increased Federal Investment in Catalysis Research............. vi I. Introduction................................................................................................ 1 A. Background, Structure, and Organization of the Workshop .................................. 1 B. Recent Advances in Experimental and Theoretical Methods ................................ 1 C. The Grand Challenge ............................................................................................. 2 D. Enabling Approaches for Progress in Catalysis ..................................................... 3 E. Consensus Observations and Recommendations.................................................. -
Andrea Deoudes, Kinetics: a Clock Reaction
A Kinetics Experiment The Rate of a Chemical Reaction: A Clock Reaction Andrea Deoudes February 2, 2010 Introduction: The rates of chemical reactions and the ability to control those rates are crucial aspects of life. Chemical kinetics is the study of the rates at which chemical reactions occur, the factors that affect the speed of reactions, and the mechanisms by which reactions proceed. The reaction rate depends on the reactants, the concentrations of the reactants, the temperature at which the reaction takes place, and any catalysts or inhibitors that affect the reaction. If a chemical reaction has a fast rate, a large portion of the molecules react to form products in a given time period. If a chemical reaction has a slow rate, a small portion of molecules react to form products in a given time period. This experiment studied the kinetics of a reaction between an iodide ion (I-1) and a -2 -1 -2 -2 peroxydisulfate ion (S2O8 ) in the first reaction: 2I + S2O8 I2 + 2SO4 . This is a relatively slow reaction. The reaction rate is dependent on the concentrations of the reactants, following -1 m -2 n the rate law: Rate = k[I ] [S2O8 ] . In order to study the kinetics of this reaction, or any reaction, there must be an experimental way to measure the concentration of at least one of the reactants or products as a function of time. -2 -2 -1 This was done in this experiment using a second reaction, 2S2O3 + I2 S4O6 + 2I , which occurred simultaneously with the reaction under investigation. Adding starch to the mixture -2 allowed the S2O3 of the second reaction to act as a built in “clock;” the mixture turned blue -2 -2 when all of the S2O3 had been consumed. -
Photoionization Studies of Reactive Intermediates Using Synchrotron
Photoionization Studies of Reactive Intermediates using Synchrotron Radiation by John M.Dyke* School of Chemistry University of Southampton SO17 1BJ UK *e-mail: [email protected] 1 Abstract Photoionization of reactive intermediates with synchrotron radiation has reached a sufficiently advanced stage of development that it can now contribute to a number of areas in gas-phase chemistry and physics. These include the detection and spectroscopic study of reactive intermediates produced by bimolecular reactions, photolysis, pyrolysis or discharge sources, and the monitoring of reactive intermediates in situ in environments such as flames. This review summarises advances in the study of reactive intermediates with synchrotron radiation using photoelectron spectroscopy (PES) and constant-ionic-state (CIS) methods with angular resolution, and threshold photoelectron spectroscopy (TPES), taking examples mainly from the recent work of the Southampton group. The aim is to focus on the main information to be obtained from the examples considered. As future research in this area also involves photoelectron-photoion coincidence (PEPICO) and threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy, these methods are also described and previous related work on reactive intermediates with these techniques is summarised. The advantages of using PEPICO and TPEPICO to complement and extend TPES and angularly resolved PES and CIS studies on reactive intermediates are highlighted. 2 1.Introduction This review is organised as follows. After an Introduction to the study of reactive intermediates by photoionization with fixed energy photon sources and synchrotron radiation, a number of Case Studies are presented of the study of reactive intermediates with synchrotron radiation using angle resolved PES and CIS, and TPE spectroscopy. -
Dehydrogenation by Heterogeneous Catalysts
Dehydrogenation by Heterogeneous Catalysts Daniel E. Resasco School of Chemical Engineering and Materials Science University of Oklahoma Encyclopedia of Catalysis January, 2000 1. INTRODUCTION Catalytic dehydrogenation of alkanes is an endothermic reaction, which occurs with an increase in the number of moles and can be represented by the expression Alkane ! Olefin + Hydrogen This reaction cannot be carried out thermally because it is highly unfavorable compared to the cracking of the hydrocarbon, since the C-C bond strength (about 246 kJ/mol) is much lower than that of the C-H bond (about 363 kJ/mol). However, in the presence of a suitable catalyst, dehydrogenation can be carried out with minimal C-C bond rupture. The strong C-H bond is a closed-shell σ orbital that can be activated by oxide or metal catalysts. Oxides can activate the C-H bond via hydrogen abstraction because they can form O-H bonds, which can have strengths comparable to that of the C- H bond. By contrast, metals cannot accomplish the hydrogen abstraction because the M- H bonds are much weaker than the C-H bond. However, the sum of the M-H and M-C bond strengths can exceed the C-H bond strength, making the process thermodynamically possible. In this case, the reaction is thought to proceed via a three centered transition state, which can be described as a metal atom inserting into the C-H bond. The C-H bond bridges across the metal atom until it breaks, followed by the formation of the corresponding M-H and M-C bonds.1 Therefore, dehydrogenation of alkanes can be carried out on oxides as well as on metal catalysts. -
Sustainable Catalysis
Green Process Synth 2016; 5: 231–232 Book review Sustainable catalysis DOI 10.1515/gps-2016-0016 Sustainable catalysis provides an excellent in-depth over- view of the applications of non-endangered elements in Michael North (Ed.) all aspects of catalysis from heterogeneous to homogene- Sustainable catalysis: with non-endangered metals ous, from catalyst supports to ligands. The Royal Society of Chemistry, 2015 Four volumes of the book series are divided into RSC Green Chemistry series nos. 38–41 two sub-topics devoted to (i) metal-based catalysts and Part 1 (ii) catalysts without metals or other endangered ele- Print ISBN: 978-1-78262-638-1 ments. Each sub-topic comprises of two books due to the PDF eISBN: 978-1-78262-211-6 detailed analysis of catalytic applications described. All Part 2 chapters are written by the world-leading researchers in Print ISBN: 978-1-78262-639-8 the area; however, covering far beyond the scope of their PDF eISBN: 978-1-78262-642-8 immediate research interests, which makes the book par- ticularly valuable for a wide range of readers. Sustainable catalysis: without metals or other Sustainable catalysis: with non-endangered metals endangered elements begins with a very brief chapter which describes the Part 1 concept of elemental sustainability, overviewing the Print ISBN: 978-1-78262-640-4 abundance of the critical elements and perspectives on PDF eISBN: 978-1-78262-209-3 sustainable catalysts. The chapters follow the groups of EPUB eISBN: 978-1-78262-752-4 the periodic table from left to right, from alkaline metals to Part 2 lead spanning 22 chapters. -
Surface Reactions and Chemical Bonding in Heterogeneous Catalysis
Surface reactions and chemical bonding in heterogeneous catalysis Henrik Öberg Doctoral Thesis in Chemical Physics at Stockholm University 2014 Thesis for the Degree of Doctor of Philosophy in Chemical Physics Department of Physics Stockholm University Stockholm 2014 c Henrik Oberg¨ ISBN 978-91-7447-893-8 Abstract This thesis summarizes studies which focus on addressing, using both theoretical and experimental methods, fundamental questions about surface phenomena, such as chemical reactions and bonding, related to processes in heterogeneous catalysis. The main focus is on the theoretical approach and this aspect of the results. The included articles are collected into three categories of which the first contains detailed studies of model systems in heterogeneous catalysis. For example, the trimerization of acetylene adsorbed on Cu(110) is measured using vibrational spectroscopy and modeled within the framework of Density Functional Theory (DFT) and quantitative agreement of the reaction barriers is obtained. In the second category, aspects of fuel cell catalysis are discussed. O2 dissociation is rate-limiting for the reduction of oxygen (ORR) under certain conditions and we find that adsorbate-adsorbate interactions are decisive when modeling this reaction step. Oxidation of Pt(111) (Pt is the electrocatalyst), which may alter the overall activity of the catalyst, is found to start via a PtO-like surface oxide while formation of a-PtO2 trilayers precedes bulk oxidation. When considering alternative catalyst materials for the ORR, their stability needs to be investigated in detail under realistic conditions. The Pt/Cu(111) skin alloy offers a promising candidate but segregation of Cu atoms to the surface is induced by O adsorption. -
Fundamentals of Theoretical Organic Chemistry Lecture 9
Fund. Theor. Org. Chem 1 SE Fundamentals of Theoretical Organic Chemistry Lecture 9 1 Fund. Theor. Org. Chem 2 SE 2.2.2 Electrophilic substitution The reaction which takes place between a reactant with an electronegative carbon and an electropositive reagent forming a polarized covalent bond is called electrophilic. In addition, if substitution occurs (i.e. there is a similar polarized covalent bond on the electronegative carbon, which breaks up during the reaction, so the reagent „substitutes” the „old” group or the leaving group) then this specific reaction is called electrophilic substitution. The electronegative carbon is called the reaction centre. In general, the good reactant are molecules having electronegative carbons like aromatic compounds, alkenes and other compounds containing electron-rich double bonds. These are called Lewis bases. On the contrary, good electrophilic reagents are electron poor compounds/molecule groups like acid-halides, which easily form covalent bond with an electronegative centre, thus creating a new molecule. These are often referred to as Lewis acids. According to molecular orbital (MO) theory the driving force for the electrophilic substitution (SE) is a Lewis complex formation involving the LUMO of the Lewis Acid Reagent and the HOMO of the Lewis Base Reactant. Reactant Reagent LUMO LUMO HOMO Lewis base Lewis acid Lewis complex Types of reactions: There are four types of reactions as illustrated below: 2 Fund. Theor. Org. Chem 3 SE Table. 2.2.2-1. Saturated Aromatic SE1 SE1 (Ar) SE2 SE2 (Ar) SE reaction on saturated atom: (1)Unimolecular electrophilic substitution (SE1): The reaction proceeds in two steps. After the departure of the leaving group, the negatively charged reaction intermediate will combine with the reagent. -
Ochem ACS Review 23 Aryl Halides
ACS Review Aryl Halides 1. Which one of the following has the weakest carbon-chlorine bond? A. I B. II C. III D. IV 2. Which compound in each of the following pairs is the most reactive to the conditions indicated? A. I and III B. I and IV C. II and III D. II and IV 3. Which of the following reacts at the fastest rate with potassium methoxide (KOCH 3) in methanol? A. fluorobenzene B. 4-nitrofluorobenzene C. 2,4-dinitrofluorobenzene D. 2,4,6-trinitrofluorobenzene 4. Which of the following reacts at the fastest rate with potassium methoxide (KOCH 3) in methanol? A. fluorobenzene B. p-nitrofluorobenzene C. p-fluorotoluene D. p-bromofluorobenzene 5. Which of the following is the kinetic rate equation for the addition-elimination mechanism of nucleophilic aromatic substitution? A. rate = k[aryl halide] B. rate = k[nucleophile] C. rate = k[aryl halide][nucleophile] D. rate = k[aryl halide][nucleophile] 2 6. Which of the following is not a resonance form of the intermediate in the nucleophilic addition of hydroxide ion to para -fluoronitrobenzene? A. I B. II C. III D. IV 7. Which chlorine is most susceptible to nucleophilic substitution with NaOCH 3 in methanol? A. #1 B. #2 C. #1 and #2 are equally susceptible D. no substitution is possible 8. What is the product of the following reaction? A. N,N-dimethylaniline B. para -chloro-N,N-dimethylaniline C. phenyllithium (C 6H5Li) D. meta -chloro-N,N-dimethylaniline 9. Which one of the reagents readily reacts with bromobenzene without heating? A.