...Module 9 : Experiments in Chemistry Lecture 38 : Titrations : Acid-Base, Redox and Complexometric Objectives In this lecture you will learn the techniques to do following Determination of the amount of sodium carbonate and sodium hydroxide in a mixture by titration. Carrying out acid-base titration using a pH meter. Carrying out acid-base titration by conductometric measurement. Determination of the composition of a mixture of acetic acid and hydrochloric acid by conductometric titration. Determination of ferrous ion using potassium dichromate by internal indicator. Determination of hardness (Ca2+ ) of water using EDTA – complexometry method. In this lecture, you will be introduced to a few experiments in chemistry. These experiments complement the theory you have learned in chemical equilibrium and kinetics. 38.1 Acid-Base Titrations: Acid-base reactions are of great practical importance in analysis, not only because of their use in titrating a large number of inorganic and organic substances, but also because the hydrogen ion concentration of a solution often is of great importance in controlling reactions. Titration : The process of determining the volume of a given solution of a reagent equivalent to the amount of another reactant present in a standard solution is known as titration. Equivalent Weight of Acids and Bases : The equivalent weight of an acid is that weight which yields one mole of hydrogen ions in the reaction employed whereas the equivalent weight of...
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...sodium carbonate accurately using the method of “weighing by difference”. Transfer the weighed carbonate to a beaker and add about 100 cm3 of distilled water to dissolve it completely. After dissolving, transfer the solution to a 250.00 cm3 volumetric flask. Rinse the beaker thoroughly and transfer all the washes into the volumetric flask. Remember not to overshoot the graduation mark of the flask. Make up the solution to the mark on the neck by adding water. Pipette 25.00 cm3 of sodium carbonate solution to a clean conical flask. Add 2 drops of methyl orange indicator to the carbonate solution. Titrate the carbonate solution with the given dilute hydrochloric acid until the colour of solution just changes from yellow to orange. Repeat the titration two times. Calculation : Results : Questions : Calculate the molarity of the sodium carbonate solution prepared and the molarity of the hydrochloric acid. 1 2. What is the meaning of “weighing by difference”? Suggest one method other than using acid-base indicator to...
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...an acid it can be titrated with a base. Titration is the process of adding a known amount of a solution of known concentration to a known amount of solution of unknown concentration. The more accurately the concentration of the solution of known concentration is known, the more accurately the concentration of the unknown solution can be determined. Some chemicals can be purchased in a pure form and remain pure over a long period or time. Other chemicals are easily contaminated by the absorption of carbon dioxide or water from the air. Sodium hydroxide absorbs moisture from the air and often appears wet. Thus if a solution of sodium hydroxide is prepared by weighing the sodium hydroxide, the concentration of the solution may not be precisely the intended concentration. Potassium hydrogen phthalate on the other hand, has a lesser tendency to absorb water from the air and when dried will remain dry for a reasonable period of time. Potassium hydrogen phthalate may be purchased in pure form at reasonable cost. Potassium hydrogen phthalate is a primary standard. This means that carefully prepared solutions of known concentration of potassium hydrogen phthalate may be used to determine, by titration, the concentration of another solution such as sodium hydroxide. The equation for the reaction of potassium hydrogen phthalate with sodium hydroxide is: KCO2C6H4CO2H + NaOH ( KCO2C6H4CO2Na + H2O The equivalence point of a titration occurs when chemically equivalent amounts...
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...an acid it can be titrated with a base. Titration is the process of adding a known amount of a solution of known concentration to a known amount of solution of unknown concentration. The more accurately the concentration of the solution of known concentration is known, the more accurately the concentration of the unknown solution can be determined. Some chemicals can be purchased in a pure form and remain pure over a long period or time. Other chemicals are easily contaminated by the absorption of carbon dioxide or water from the air. Sodium hydroxide absorbs moisture from the air and often appears wet. Thus if a solution of sodium hydroxide is prepared by weighing the sodium hydroxide, the concentration of the solution may not be precisely the intended concentration. Potassium hydrogen phthalate on the other hand, has a lesser tendency to absorb water from the air and when dried will remain dry for a reasonable period of time. Potassium hydrogen phthalate may be purchased in pure form at reasonable cost. Potassium hydrogen phthalate is a primary standard. This means that carefully prepared solutions of known concentration of potassium hydrogen phthalate may be used to determine, by titration, the concentration of another solution such as sodium hydroxide. The equation for the reaction of potassium hydrogen phthalate with sodium hydroxide is: KCO2C6H4CO2H + NaOH ( KCO2C6H4CO2Na + H2O The equivalence point of a titration occurs when chemically equivalent amounts...
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...EXPERIMENT 1 DETERMINATION OF DISSOLVED OXYGEN IN WATER INTRODUCTION The dissolved oxygen content is an important index when considering its suitability for town supply. A good clean potable water will give dissolved oxygen value close to the theoretical value for the saturated solution of oxygen in water. When there is pollution from organic matter and other trade effluents, the dissolved oxygen is up in various biochemical oxidation processes and its is only slowly replaced through surface absorption. Such water will give a low dissolved oxygen content until oxidation is completed. Adequate dissolved oxygen is necessary for the life of fish and other aquatic organisms. The methods described below for the determination of oxygen in water is based on that devised by Winkler. When manganese hydroxide is precipitated in the water sample it is quickly oxidized to higher hydrated oxides (probably in the four valent state) by the dissolve oxygen. Iodine, equivalent to the dissolved oxygen content, is then liberated on acidification in the presence of iodine, and it may be titrated with standard thio‐sulphate. INTERFERENCES AND PRE – TREATMENT Most oxidising and reducing substances e.g dissolved organic substances, nitrite ions, higher‐valency manganese compounds, active chlorine, sulphide and sulphite ions, iron (II) and irons interfere. The influence of the dissolved organic substances can be excluded by conversion of the manganese hydroxides...
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...29 EXPERIMENT 3. ACID-BASE TITRATIONS: DETERMINATION OF CARBONATE BY TITRATION WITH HYDROCHLORIC ACID BACKGROUND Carbonate Equilibria In this experiment a solution of hydrochloric acid is prepared, standardized against pure sodium carbonate, and used to determine the percentage of carbonate in a sample. An aqueous solution of hydrochloric acid is almost completely dissociated into hydrated protons and chloride ions. Therefore, in a titration with hydrochloric acid the active titrant species is the hydrated proton. This species is often written H3O+, although the actual form in solution is more correctly (H2O)nH+. For convenience we designate it simply H+. Carbonate in aqueous solution acts as a base; that is, it is able to accept a proton to form bicarbonate ion. 2CO3 + H+ HCO3 (1) Bicarbonate is able to combine with another proton to form carbonic acid: HCO3 + H+ H2CO3 (2) Equilibrium expressions for the dissociation of bicarbonate and carbonic acid may be written 2[H+] [CO3 ] K2 = (3) [HCO3] [H+] [HCO3] [H2CO3] and K1 = (4) 30 where K1 and K2 are the first and second acid dissociation constants for H2CO3; the experimentally determined values are K1 = 3.5 x 10-7 and K2 = 5 x 10-11. When successive protonation reactions such as (1) and (2) occur, the extent to which the first reaction proceeds before the second begins depends on the difference between the two acid dissociation constants. By combination of Equations (3) and (4) with those for charge and...
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...determination of the analyte calcium was possible due to the stable and quick formation of the metal-EDTA complex with a 1:1 reaction stoichiometry. Flame atomic absorption analysis is useful in determining the amount of analyte in an unknown because the measure absorbances of standard solutions can be used to plot a calibration curve that can be used to determine the concentration of the metal in an unknown solution. Potentiometry is useful for determination of analyte when an ion sensitive electrode is used to find the amount of ion in standard solutions. Week 1: Introduction and Background The first test for calcium in the multivitamin was complexometric titrimetry, a titration of a solution of calcium tablet with a standardized solution of EDTA. EDTA forms a stable complex with calcium metal with a reaction stoichiometry of 1:1, so an EDTA titration can be used to quantitatively determine the metal ion concentration of calcium in a calcium tablet solution. The formation of calcium-EDTA complex is pH-dependent and needs to be buffered to pH so that formation can be quantitatively determined. A Calmagite indicator is used to determine the endpoint of the titration. A colored complex is formed...
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...Preparation of Buffers for Use in Enzyme Studies (by G. Gomori) The buffers described in this section are suitable for use either in enzymatic or histochemical studies. The accuracy of the tables is within ± 0.05 pH at 23 ºC. In most cases the pH values will not be off by more than ± 0.02 pH even at 37 ºC and at molarities slightly different from those given (usually 0.05 M). The methods of preparation described are not necessarily identical with those of the original authors. The titration curves of the majority of the buffers recommended have been redetermined by the writer. The buffers are arranged in the order of ascending pH range. 1. Hydrochloric Acid-Potassium Chloride Buffer. Stocks solutions A: 0.2 M solution of KCl (14.91 g in 1 L) B: 0.2 M HCl 50 mL of A + x mL of B, diluted to a total of 200 mL x 97.0 78.0 64.5 51.0 41.5 33.3 26.3 20.6 16.6 13.2 10.6 8.4 6.7 jun 14, 2004 pH 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 Pag.1 2. Glycine-HCl Buffer. Stocks solutions A: 0.2 M solution of glycine (15.01 g in 1 L) B: 0.2 M HCl 50 mL of A + x mL of B, diluted to a total of 200 mL x 5.0 6.4 8.2 11.4 pH 3.6 3.4 3.2 3.0 x 16.8 24.2 32.4 44.0 pH 2.8 2.6 2.4 2.2 3. Phthalate-Hydrochloric Acid Buffer. Stocks solutions A: 0.2 M solution of potassium acid phthalate (40.48 g in 1 L) B: 0.2 M HCl 50 mL of A + x mL of B, diluted to a total of 200 mL x 46.7 39.6 33.0 26.4 20.3 pH 2.2 2.4 2.6 2.8 3.0 x 14.7 9.9 6.0 2.63 pH 3.2 3.4 3.6 3.8 4. Aconitate Buffer. Stocks solutions...
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...BIOL 3380 Name:_____________________________________ Circle Session: T-PM W-AM W-PM R-AM R-PM F-AM F-PM Experiment 9 – Pre-lab Homework Enzyme Kinetics of LDH This pre-lab homework assignment is due at the beginning of your lab session. You are provided with the following portion of a protocol: • Determine concentration of enzyme stock solution, if unknown, by taking an A280 nm reading of a 1:100 dilution (in water). Use a total volume of 1 ml in the cuvette. • Dilute some of the enzyme stock with buffer A to make a 4 mg/ml solution. • Serially dilute the 4 mg/ml solution with buffer A to make working solutions of 400 µg/ml and 40 µg/ml. • Prepare 30 µl of each working solution for every sample The PI of the lab gives you a tube of enzyme and tells you the following before disappearing into the office to write more grant proposals: ➢ There is 50 µl of enzyme stock solution. The enzyme is expensive to purify, so follow the protocol exactly, using as little of the stock solution as possible. ➢ The concentration of the stock solution is currently not known, but a 1 mg/ml concentration of the pure enzyme has an A280 nm of 2.0. ➢ You’ll be performing the assay on 12 samples. ➢ Make enough of each working solution so that you have at least 400 ul to work with when you do the assay (to cover any waste and/or inefficiencies in pippetting). Using the spectrophotometer to read the absorbance at 280 nm, you get...
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...See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/223357366 Cloud-point extraction of lead in saliva via use of non-ionic PONPE 7.5 without added chelating agent ARTICLE in TALANTA · FEBRUARY 2000 Impact Factor: 3.51 · DOI: 10.1016/S0039-9140(99)00252-0 · Source: PubMed CITATIONS DOWNLOADS VIEWS 77 369 333 4 AUTHORS, INCLUDING: Maria Fernanda Silva Liliana P Fernández National University of Cuyo Universidad Nacional de San Luis 17 PUBLICATIONS 363 CITATIONS 43 PUBLICATIONS 540 CITATIONS SEE PROFILE SEE PROFILE Available from: Maria Fernanda Silva Retrieved on: 08 September 2015 Talanta 51 (2000) 123 – 129 www.elsevier.com/locate/talanta Cloud point extraction of lead in saliva via use of nonionic PONPE 7.5 without added chelating agents Marta O. Luconi, M. Fernanda Silva, Roberto A. Olsina, Liliana P. Fernandez * ´ Area of Analytical Chemistry, National Uni6ersity of San Luis, CONICET, San Luis 5700, Argentina Received 4 March 1999; received in revised form 13 August 1999; accepted 16 August 1999 Abstract A new micelle-mediated phase separation of metal ions to preconcentrate trace levels of lead as a prior step to its determination by flame atomic spectroscopy has been developed. The methodology is based on the cloud point extraction of lead with PONPE 7.5 in the absence of chelating agent. The chemical variables affecting the sensitivity ...
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...Chemistry Modern Analytical Chemistry David Harvey DePauw University Boston Burr Ridge, IL Dubuque, IA Madison, WI New York San Francisco St. Louis Bangkok Bogotá Caracas Lisbon London Madrid Mexico City Milan New Delhi Seoul Singapore Sydney Taipei Toronto McGraw-Hill Higher Education A Division of The McGraw-Hill Companies MODERN ANALYTICAL CHEMISTRY Copyright © 2000 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of the publisher. This book is printed on acid-free paper. 1 2 3 4 5 6 7 8 9 0 KGP/KGP 0 9 8 7 6 5 4 3 2 1 0 ISBN 0–07–237547–7 Vice president and editorial director: Kevin T. Kane Publisher: James M. Smith Sponsoring editor: Kent A. Peterson Editorial assistant: Jennifer L. Bensink Developmental editor: Shirley R. Oberbroeckling Senior marketing manager: Martin J. Lange Senior project manager: Jayne Klein Production supervisor: Laura Fuller Coordinator of freelance design: Michelle D. Whitaker Senior photo research coordinator: Lori Hancock Senior supplement coordinator: Audrey A. Reiter Compositor: Shepherd, Inc. Typeface: 10/12 Minion Printer: Quebecor Printing Book Group/Kingsport Freelance cover/interior designer: Elise Lansdon Cover image: © George Diebold/The...
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...ANALYSIS OF FOOD PRODUCTS FOOD SCIENCE 581 Instructor Prof. D. Julian McClements Room 238, Chenoweth Lab Tel: 545 1019 Email: mcclements@foodsci.umass.edu Course Description Food products are analyzed for a variety of reasons, e.g., compliance with legal and labeling requirements, assessment of product quality, determination of nutritive value, detection of adulteration, research and development. The lectures will cover the basic principles of analytical procedures and techniques commonly used to provide information about the chemical composition, structure and physical properties of food materials. The aim of the laboratory classes is to give students experience in performing food analysis experiments, analyzing data and reporting their findings. In addition, students are expected to work in teams on a special project where they will identify and critically assess the most appropriate analytical methods for analyzing the properties of a particular food product. [4 Credits]. Textbooks * Introduction to Food Analysis. S.S. Nielsen, 1998. Aspen Publishers - The best general overview of food analysis techniques currently available. (Required). * Food Analysis: Theory and Practice. Y. Pomeranz and C.E. Meloan, Chapman and Hall - General overview of food analysis techniques (Useful) * Food Analysis: Principles and Techniques. D.W. Gruenwedel and J.R. Whitaker, Marcel Dekker - General overview of food analysis techniques (Useful) * Analytical Chemistry of Foods...
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...AP Biology Exam Review: Lab Essays At least one essay (FRQ) on the exam will be based on an AP laboratory. To prepare for this question, review the objectives for all twelve laboratory exercises. The College Board does not necessarily expect that you have completed that lab, but rather that you have investigated the objectives of the lab. You may be asked to “design an experiment to determine….” You don’t necessarily need to create a new lab; if you have done an activity that would answer the question, simply describe it. For a good response, you should include the following. 1. State a hypothesis [as an “if…..(conditions), then….(results)” statement] Be sure your hypothesis is testable. 2. Identify the variable factor. 3. Identify the control. Be certain to explain the control for the experiment. 4. Hold all other variables constant. 5. Manipulate the variable. 6. State how you would measure the results. 7. Discuss the expected results. Relate the results to your hypothesis. 8. Include steps to replicate or verify. You may be asked to graph data. Be sure to use a graph that is appropriate for you data. Bar graphs are used when data points are discrete (not related to one another), while line graphs are used with the data are continuous. If there is a data point at zero, be certain to extend your line to 0, but do not extend the line to 0 if there is no data point at zero. Other points to keep in mind: ...
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...Chemistry Notes 2010 Core Module 1: Production of Materials Contextual Outline Humans have always exploited their natural environment for all their needs including food, clothing and shelter. As the cultural development of 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)...
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...FORMULATION AND EVALUATION OF TOPICAL GEL CONTAINING AZITHROMYCIN AND PREDNISOLONE VESICLES FOR TREATING PSORIASIS Sonia Tomar, Tinku Singhal, ABSTRACT Psoriasis is a chronic, autoimmune systemic inflammatory disease, associated with metabolic syndrome, cerebrovascular disease, diabetes and many other diseases. There is various type of psoriasis but most common type of psoriasis is caused by Psoriasis vulgaris. It is characterized by rigid of skin due to increase in the level of cholesterol and fall in the level of ceramide. Apart from that it is associated with an immune system of the body means movement of immune cells from dermis to the epidermis, where they stimulate skin cells (keratinocytes) to proliferate. Various type of drug delivery system are used for the treatment of psoriasis including topical, oral or systemic but gels prepration of azithromycin and prednisolone are more effective in reduction of purities, scaling and hyperkeratosis of psoriasis plaque. Niosomal/Vesicular gel, has been explored extensively for topical application to enhance skin penetration as well as skin retention. Prednisolone and azithroycin together provide effective results in the treatment of psoriasis. Due to high entrapment efficiency and stability, gel prepration (Azithromycin & Prednisolone) reduce the scaly patches and suppression of humoral immunity. Keywords: Niosome, Immunity, Topical, Psoriasis, Gel, Azithromycin, Prednisolone. INTRODUCTION Psoriasis is recognized...
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