...Purpose The main objective of this experiment was to experimentally derive the equilibrium constant for the reaction between iron (III) and thiocyanate ions. The second objective of this experiment was to use the spectrophotometer to measure the absorbance of light by [FeSCN2+] at various concentrations and then to plot its corresponding calibration curve to mathematically determine the concentration of [FeSCN2+] at equilibrium. The final objective of this experiment was to observe Le Chatelier’s Principle when stress was applied to the reaction between iron (III) and thiocyanate ions and to determine in which direction the react shifted to maintain equilibrium. Introduction Chemical reactions do not always run to completion, such that the entire limiting reagent or all reactants are consumed entirely. In many cases many chemical reactions establish an equilibrium, where the amount of reactants and products are constantly in flux in an effort to maintain a set amount. At equilibrium the rate of the forward reaction equals the rate of the reverse reaction. Le Chatelier’s Principle states that if any stress is applied to the reaction when it is at equilibrium, the reaction will shift in order to re-obtain equilibrium. The resulting shift can either be a reduction or increase in the amount of product or the reactant. If there is a decrease in the amount of reactant and an increase in the amount of product the reaction has shifted...
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...185 EQUILIBRIUM 185 UNIT 7 EQUILIBRIUM After studying this unit you will be able to • identify dynamic nature of equilibrium involved in physical and chemical processes; • state the law of equilibrium; • explain characteristics of equilibria involved in physical and chemical processes; • write expressions for equilibrium constants; • establish a relationship between Kp and K c ; • explain various factors that affect the equilibrium state of a reaction; • classify substances as acids or bases according to Arrhenius, Bronsted-Lowry and Lewis concepts; • classify acids and bases as weak or strong in terms of their ionization constants; • explain the dependence of degree of ionization on concentration of the electrolyte and that of the common ion; • describe pH scale for representing hydrogen ion concentration; • explain ionisation of water and its duel role as acid and base; • describe ionic product (Kw ) and pKw for water; • appreciate use of buffer solutions; • calculate solubility product constant. Chemical equilibria are important in numerous biological and environmental processes. For example, equilibria involving O2 molecules and the protein hemoglobin play a crucial role in the transport and delivery of O2 from our lungs to our muscles. Similar equilibria involving CO molecules and hemoglobin account for the toxicity of CO. When a liquid evaporates in a closed container, molecules with relatively higher kinetic energy escape the liquid surface into the vapour...
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...Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a solution of the solute in the solvent Solubility is defined as the ability of one substance to dissolve within another substance. What Affects Solubility? One of the factors that has a profound impact on solubility is temperature. Temperature, a measure of the available thermal energy, can increase the solubility of solids in liquids. This phenomenon can be observed in the creation of supersaturated solutions, or mixtures that contain far more of the solid dissolved in a liquid than would be possible under room temperature conditions. One application of supersaturated solutions can be seen in the production of rock candy where high-temperature sugar solutions readily form sugar crystals on the surface of objects placed in the solution. For gases that are dissolved in liquids, however, the trend is just the opposite. Cooler temperatures increase the solubility of gases in liquids, and higher temperatures decrease the solubility of gases. An example of the effect of temperature on dissolved gases can be found in the loss of dissolved oxygen in lakes or streams during extremely hot weather, a condition that results in the death of fish. In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a separate phase (as a...
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...CHEMISTRY CHEMISTRY (CLASSES XI–XII) Rationale Higher Secondary Stage is the most crucial stage of school education because at this stage specialised discipline based, content oriented courses are introduced. Students reach this stage after 10 years of general education and opt for Chemistry with a purpose of mostly for pursuing their career in basic sciences or professional courses like medicines, engineering, technology and studying courses in applied areas of science and technology at tertiary level. Therefore, at this stage, there is a need to provide learners with sufficient conceptual background of Chemistry, which will make them competent to meet the challenges of academic and professional courses after the higher secondary stage. National Curriculum Framework for School Education – 2005 recommends a disciplinary approach with appropriate rigour and depth with the care that syllabus is not heavy and at the same time it is comparable to the international level. It emphasizes a coherent focus on important ideas within the discipline that are properly sequenced to optimize learning. It recommends that theoretical component of Higher Secondary Science should emphasize on problem solving methods and the awareness of Syllabus for Secondary and Higher Secondary Levels 22 historical development of key concepts of science be judiciously integrated into content. The present exercise of syllabus development in Chemistry at Higher Secondary Stage is based on this framework...
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...Introduction: What is the importance of maintaining a constant pH of a pool to ensure a safe/clean pool? There are several ways in which a pool may become contaminated by bad bacteria. The pool must be maintained to stop the spread of disease as well as be comfortable for swimming in. They need disinfectants to destroy the micro-organisms present and filtration to keep the water clean. Most of the chemicals are extremely pH dependant and have a certain optimal pH range that they are most effective in. This article will investigate the importance of pH in pools as well as the equilibrium reactions happening between chemicals. It will investigate the reacts occurring in the pool and what makes a pool safe to swim. As well as the importance of maintaining the pool. Chlorination: Chlorination in pools is the most common form of disinfection for swimming pools. Pools are chlorinated because chlorine is extremely effective of killing bacteria. In the form of hypochlorous acid, chlorine kills bacteria by attacking the cell walls and destroying the cell itself. There are several ways to introduce chlorine into the pool. These include: tablets, powdered chlorine, or a salt chlorine generator which converts table salt into chlorine. The most common way of introducing...
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...SCH 4U1 | Equilibrium and Le Châtelier’s Principle | | Introduction: Chemical equilibrium is the state of a reaction in which all reactants and products have reached constant concentrations in a closed system (DiGiuseppe, Haberer, Salciccioli, Sanader, & Vavitsas, 2012, p. 420). Chemical reactions will occur until the reaction reaches a point where the concentrations of the products and reactants become constant. Le Châtelier's principle states that chemical systems at equilibrium shift in the direction that opposes the change when a change occurs that disturbs the equilibrium (DiGiuseppe, Haberer, Salciccioli, Sanader, & Vavitsas, 2012, p. 439). In the lab activity performed, the effects of changing temperature and volume of a system were observed and recorded for the endothermic reaction of dinitrogen tetroxide with 57.2 kJ of energy: N2O4(g) + 57.2 kJ ↔2 NO2(g) Colourless Reddish-Brown As well, the effects of modifying the concentrations of the reactants and products of a system were observed and recorded for the reaction of iron (II) thiocyanide: Fe3+(aq)+SCN1-(aq)↔Fe(SCN)2+(aq) In each case, as our hypotheses predicted, the reactions shifted in the direction that restored equilibrium to the system. Discussion: Concentration: The effects that would be observed on a system at equilibrium all depend on whether products or reactants are added or removed. If products or reactants are added, the equilibrium shifts in the direction...
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...CHEMICAL EQUILIBRIUM Equilibrium occurs when the rate of the forward reaction is equal to the rate of reverse reaction. Concentration of the reactants and the products remain the same. Dynamic equilibrium occurs when the processes do not stop and forward and reverse reactions still continue in both directions at the same rate. A homogeneous reaction is a reaction wherein all the reactants and products are in the same phase e.g. all are gases. A heterogeneous reaction is a reaction wherein all the reactants and products are not in the same phase. If there is no interaction between the system and its surroundings, i.e., a system from which no substances in the reaction can escape, we say it is a closed system. Calculation of the substance amount and concentration at equilibrium We can determine the concentration of the substance by dividing the number of mol of the substance at that stage of the reaction by the volume of the container in dm3, i.e.: c= n/V where c or [ ] = concentration of the substance in mol.dm-3 n = number of mol of the substance V = volume of the container in dm3 It is handy to use a table to determine these values. Example 1 A mixture of 5 mol H2(g) and 6 mol I2(g) are placed in a sealed container of 2 dm3 at a temperature of 4580C. The balanced chemical equation for the reaction is: Equilibrium is reached after a certain time. At equilibrium there is 4mol HI(g) in the container. Calculate the concentrations...
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...Determining the equilibrium constant from pH values of changing concentrations of ethanoic acid Design Research question: How will altering the concentrations of ethanoic acid affect the pH value, and, in-turn, the equilibrium constant? Background information: When weak acids react, the reaction typically does not go to completion. Rather, the system goes to an intermediate state in which the rates of the forward and reverse reactions are equal. Such a system is said to be in chemical equilibrium. When equilibrium is reached, the reactants and the products have concentrations which do not change with time. When in equilibrium at a particular temperature, a reaction mixture obeys the Law of Chemical Equilibrium, which imposes a condition on the concentrations of reactants and products. This condition is expressed in the equilibrium constant Kc for the reaction. In this experiment, I will study the equilibrium properties of the reaction between ethanoic acid, otherwise known as acetic acid (CH3COOH) and water (H2O): CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq) When solutions containing ethanoic acid and water are mixed, they react to some extent, forming CH3COO- and H3O+. As a result of the reaction, the equilibrium amounts of CH3COOH and H2O will be less; for every mole of CH3COO- formed, one mole of CH3COOH and one mole of H2O will react. The equilibrium constant expression Kc for Reaction 1 is: Kc = [CH3COOH] / [H3O+][CH3COO-] The value of...
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...Lab section: Thursday 6 pm Date: May 7, 2015 Abstract In this experiment, the burette was used to titrate sodium chloride solution by adding different amount of silver nitrate solution. The electrochemical potential was measured by a reference electrode in order to understand the Nernst equation and calculate out experimental result of concentration of silver nitrate solution, Ksp of Ag ion, and the concentration of chloride ion in the unknown sodium chloride solution. There are four titration performed in this experiment, 2 rough titration of both 150 ppm and unknown sodium chloride solution and 2 careful...
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...CH 111: General Chemistry Dr. Ananda M The University of Dodoma, Tanzania Teaching Compendium on General Chemistry (CH 111) by Dr. AnandaMurthyM.Sc., M.Phil., Ph.D. Department of Chemistry, School of Physical Sciences, College of Natural &Mathematical Sciences, The University of Dodoma. UDOM- Study Material 2013-14 Page 1 CH 111: General Chemistry Dr. Ananda M Preface The importance of learning chemistry cannot be overemphasized. In this regard, all branches of chemistry contribute to the overall role that chemistry plays in daily life. The course content of CH 111 is designed to bridge the gap between the high school and the undergraduate chemistry, with respect to some fundamental topics in chemistry for first year chemistry students. This compendium will be helpful to the students, due to its relevance to the course content and will promote better understanding of the subject matter. It is intended to enable students to achieve the learning objectives and learning outcomes of CH 111 by being a quick reference to learners. The author of the compendium has presented the contents in a simplified manner by using various illustrations, including structures, tables, figures, and other relevant information to help the learner understand easily. This compendium will, to greater extent, help in understanding the basic concepts in chemistry. Dr. J.J. Makangara Senior Lecturer, Department of Chemistry, Former Dean, School of Physical Sciences, College...
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...The equilibrium between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4, is shown below. 2NO2(g) [pic] N2O4(g) Kc = 0.01 What happens when the volume of a mixture at equilibrium is decreased at a constant temperature? I. The value of Kc increases II. More N2O4 is formed III. The ratio of [pic] decreases A. I and II only B. I and III only C. II and III only D. I, II and III (Total 1 mark) 2. Which statement about chemical equilibria implies they are dynamic? A. The position of equilibrium constantly changes. B. The rates of forward and backward reactions change. C. The reactants and products continue to react. D. The concentrations of the reactants and products continue to change. (Total 1 mark) 3. Methanol may be produced by the exothermic reaction of carbon monoxide gas and hydrogen gas. CO(g) + 2H2(g) [pic] CH3OH(g) ∆HO = –103 kJ (a) State the equilibrium constant expression, Kc, for the production of methanol. ...................................................................................................................................... ...................................................................................................................................... (1) (b) State and explain the effect of changing the following conditions on the amount of methanol present at equilibrium: ...
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...humans continued, they looked for a greater variety of materials to cater for their needs. The twentieth century saw an explosion in both the use of traditional materials and in the research for development of a wider range of materials to satisfy technological developments. Added to this was a reduction in availability of the traditional resources to supply the increasing world population. Chemists and chemical engineers continue to play a pivotal role in the search for new sources of traditional materials such as those from the petrochemical industry. As the fossil organic reserves dwindle, new sources of the organic chemicals presently used have to be found. In addition, chemists are continually searching for compounds to be used in the design and production of new materials to replace those that have been deemed no longer satisfactory for needs. This module increases students’ understanding of the implications of chemistry for society and the environment and the current issues, research and developments in chemistry. 1.1 Construct word and balanced formulae equations of all chemical reactions as they are encountered in this module: • Acid reactions: o acid (aq) + base (aq) salt (aq) + water (l) o acid (aq) + active metal (s) salt (aq) + hydrogen (g) o acid (aq) + metal carbonate (s) salt (aq) + water (l) + carbon dioxide (g) • Cracking of long chain alkanes (e.g. decane) to give a shorter chain alkene & alkane o Thermal cracking (heated with steam in absence of O2 to 750-900°C)...
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...activation process. The hazelnut was pyrolyzed at 250 and 700 °C. For determining the capture speed of the adsorbents, the pseudo-first- and second-order kinetic studies were performed. The Freundlich and Langmuir isotherm models were used to determine adsorption equilibrium. The surface characterization of hazelnut shell and activated carbon was determined by Brunauer-Emmett-Teller (BET) analysis and FTIR spectrum. Pb+2 adsorption capacity of obtaining activated carbon was determined by ICP-OES analysis. The raw hazelnut shell’s BET surface area is 5.92 m2/g and the surface area of activated carbons which is pyrolyzed at 250 and 700 °C were determined (270.2 and 686.7 m2/g, respectively. The surface area of hazelnut shell, which pyrolyzed at 700 °C after being activated with ZnCl2, was determined to be 736.49 m2/g. Results show that physical adsorption process is dominant for the activated carbon pyrolysis at 700 °C but the chemical adsorption is dominant for the activated carbon pyrolysis at lower degrees and for raw hazelnut shell. Keywords Activated carbon . Heavy metals . Lead(II) . Kinetic . Isotherm . Hazelnut Responsible editor: Philippe Garrigues A. Şencan (*) : M. Karaboyacı Department of Chemical Engineering, Süleyman...
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...capacity (which is determined under static conditions) and the dynamic exchange capacity (which is determined by passing a solution through a bed of the exchanger). The exchange capacity depends on the number of functional group per gram of the exchanger. The extent of the use of the total exchange capacity depends on the level of ionization of the functional groups of the exchanger, on the chemical and physical conditions of the process, and hydrated ionic radii and selectivity. The operating or breakthrough capacity of a column type ion exchange system depends on its design and operating parameters, the concentration of the ions being removed and the effects of interference from other ions, nature of the functional group on the exchanger, degree of cross-linking, ionic valence, ionic size and temperature. In a column system this generally refers to the volume of the solution that can be treated before a sharp increase in the effluent concentration of the species being removed is...
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...able to deal comprehensively with the large content in CHM 1101. It is hoped that by providing this paper, students will not need to make lots of notes in lectures and so they can focus on grasping the concepts taught. The document is meant to be a guide to the topics covered in CHM 1101 and is by no means exhaustive. Students are still required to attend classes regularly and punctually and to engage meaningfully in lectures and tutorials. Further, supplemental reading of these topics in any good General Chemistry text is expected. Dawn Fox Medeba Uzzi 2 SECTION 1 – Modules A – D: section deals with the foundation for chemistry. It introduces students to matter & its classification, Atom & its structure, Periodic table and chemical rxns. Introduction to Science and Measurement What is Chemistry? – Chemistry is the study of matter and its transformations Natural sciences refer to the systematic study of the natural world (our earth, the universe and ourselves). The place of chemistry in the Natural sciences What is matter? Matter is anything occupying space and having mass. Since chemistry is the study of matter there must be a logical way to go about studying nature or we will reap confusion. This is called the Scientific Method. The scientific method is a framework for gaining and organizing knowledge. It...
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