...12.097 Environmental Chemistry of Boston Harbor – IAP 2006 Lab 1: DETERMINATION OF DISSOLVED OXYGEN BY WINKLER TITRATION 1. Background Knowledge of the dissolved oxygen (O2) concentration in seawater is often necessary in environmental and marine science. It may be used by physical oceanographers to study water masses in the ocean. It provides the marine biologist with a means of measuring primary production - particularly in laboratory cultures. For the marine chemist, it provides a measure of the redox potential of the water column. The concentration of dissolved oxygen can be readily, and accurately, measured by the method originally developed by Winkler in 1888 (Ber. Deutsch Chem. Gos., 21, 2843). Dissolved oxygen can also be determined with precision using oxygen sensitive electrodes; such electrodes require frequent standardization with waters containing known concentrations of oxygen. They are particularly useful in polluted waters where oxygen concentrations may be quite high. In addition, their sensitivity can be exploited in environments with rapidly-changing oxygen concentrations. However, electrodes are less reliable when oxygen concentrations are very low. For these reasons, the Winkler titration is often employed for accurate determination of oxygen concentrations in aqueous samples. 2. Scope and field of application This procedure describes a method for the determination of dissolved oxygen in aqueous samples, expressed as mL O2 (L water)...
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...Analytical Chemistry Laboratory I Fall Semester University of Massachusetts Lowell Department of Chemistry Determination of equivalence point using pH titration of Potassium Hydrogen Phalate and 0.1 N Sodium Hydroxide with phenolphthalein indicator By Lee Binks (12647892), Penny Jinks (12993456) and Hong Links 13504733) Date submitted: Sept 18th , 2013 Abstract- The experiment described elucidates the fundamental principle of potentiometric titrations and determination of equivalence point using pH titration of Potassium Hydrogen Phalate and 0.1 N Sodium Hydroxide with the use of phenolphthalein indicator. The present study revealed the equivalence point by using simple titration curve which was further confirmed by using first and second derivative plots and pKa value of the Potassium Hydrogen Phalate. Introduction- The pH meter measures the pH of a solution and provides a direct method of obtaining a titration curve which is a graph of measured pH values versus the volume of titrant added in milliliters. The equivalence point is the point at which a stoichiometrically equivalent amount of base has been added to the acid. It does not mean that pH will be necessarily 7. KHP is a monoprotic acid. The neutralization with NaOH takes place in a 1:1 ratio HOOCC6H4COOK (aq) + NaOH ( aq) ---> C6H4 ( COO)2 2- (aq) + K+ (aq) + Na+ (aq)...
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...Fat and Oil Peroxide value of Oleic acid Redox titration by Automatic Potentiometric Titrator Standard Test Method for Analysis of Basic Fatty Material ISO 3960 1. Abstract The oleic acid is widely distributed in plant and animal fats. Measurement of peroxide value (POV) of oleic acid is demonstrated in this application according to the below quoted test method. The test sample is first dissolved in mixture of chloroform and acetic acid（2：3）. By flowing nitrogen gas through the sample to dispel residual oxygen, add potassium iodide, and then titrate free iodine with 0.01mol/L sodium thiosulfate. The endpoint is determined by the maximum inflexion point on titration curve. POV is calculated from titration volume of sodium thiosulfate. I2 + 2Na2S2O3 → Na2S4O6 + 2NaI 2. Reference 1) Test Method for Analysis of Basic Fatty Material by Japanese Oil Chemistry Society; Reference material 2.4-1996 Peroxide value （Chloroform Method） 2) ISO 3960 : 2007 Animal and vegetable fats and oils – Determination of peroxide value 3. Cautions in measurement 1) Do not use water containing carbon dioxide in preparing saturated potassium iodide solution. 2) To confirm saturation, add excessive potassium iodide to the saturated potassium iodide solution, and leave crystal in the solution. 3) Prepare fresh saturated potassium iodide each time. 4) If the sample does not change color to yellow due to free iodine when saturated potassium iodide is added, add more saturated potassium iodide...
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...NATIONAL QUALIFICATIONS CURRICULUM SUPPORT Chemistry A Practical Guide Support Materials [REVISED ADVANCED HIGHER] [pic] The Scottish Qualifications Authority regularly reviews the arrangements for National Qualifications. Users of all NQ support materials, whether published by Education Scotland or others, are reminded that it is their responsibility to check that the support materials correspond to the requirements of the current arrangements. Acknowledgement © Crown copyright 2012. You may re-use this information (excluding logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/ or e-mail: psi@nationalarchives.gsi.gov.uk. Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned. Any enquiries regarding this document/publication should be sent to us at enquiries@educationscotland.gov.uk. This document is also available from our website at www.educationscotland.gov.uk. Contents Introduction 5 Chemical analysis 6 Qualitative and quantitative analysis 6 Volumetric analysis 6 Gravimetric analysis 14 Colorimetric analysis 17 Organic techniques 22 Introduction 22 Preparation 22 Isolation 24 Purification 29 Identification...
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...out in a flask containing the liquid or dissolved sample. Titrant solution is volumetrically delivered to the reaction flask using a burette. Delivery of the titrant is called a titration. The titration is complete when sufficient titrant has been added to react with all the analyte. This is called the equivalence point. An indicator is often added to the reaction flask to signal when all of the analyte has reacted. The titrant volume where the signal is generated is called the end point. The equivalence and end points are rarely the same. SUCCESSFUL TITRATIONS A few rules of thumb for designing a successful titration are: 1. The titrant should either be a standard or should be standardized. 2. The reaction should proceed to a stable and well defined equivalence point. 3. The equivalence point must be able to be detected. 4. The titrant’s and sample’s volume or mass must be accurately known. 5. The reaction must proceed by a definite chemistry. There should be complicating side reactions. 6. The reaction should be nearly complete at the equivalence point. In other words, chemical equilibrium favors products. 7. The reaction rate should be fast enough to be practical. TYPES OF TITRATIONS 1. ACID-BASE TITRATION a. These titrations are based on the neutralization reaction that occurs between an acid and a base, when mixed in solution. b. The acid (resp....
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...solution can be standardized by titration against a standard solution of ammonium iron(II) sulphate solution. This is an example of standardization, which is a process to determine the concentration of a solution by using it to titrate another solution which have a known concentration. This titration is known as redox titration as the titrant, which is the potassium permanganate is a strong oxidizing agent. The ammonium iron (II) sulphate solution is measured by using a pipette and transfer it into a conical flask while the potassium permanganate solution is placed in a burette. The ammonium iron (II) sulphate solution is made acidic by adding dilute sulphuric acid. Potassium permanganate solution is dark purple colour because of the presence of permanganate ions, MnO4- . Since potassium permanganate is a strong oxidizing agent, it can oxidizes iron(II) ions to iron(III) ions. Fe2+ Fe3+ + e- On the other hand, the Mn7+ ions of the dark purple colour permanganate ion, MnO4- are reduced to colourless Mn2+ ion. MnO4- + 8H+ + 5e- Mn2+ +4H2O As a result, the overall ionic equation is: MnO4- + 8 H+ + 5 Fe2+ → Mn2+ + 5 Fe3+ + 4 H2O At the end point of the titration, the colourless solution in the conical flask will change to pale pink colour. As a result, no indicator is needed. Iron (II) sulphate heptahydrate crystals, FeSO4 . 7H2O, which is a common reducing agent is not suitable to be used in this titration because it will easily oxidizes...
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...Malaysia. Accepted 14 May, 2010 An investigation was carried out on students’ study habit in volumetric analysis at the senior secondary school level in Ondo State. A descriptive research design was adopted in the study. Questionnaire on study habit inventory was adapted and used to collect information from the respondents at various sampled schools. The sample comprised 240 senior secondary II chemistry students drawn from six schools in Akure South Local Government Area of Ondo State. The hypotheses investigated with respect to students’ study habit problems such as home work/ assignment, reading and note-taking, students’ concentration, time allocation, teachers’ consultation as human variables were analyzed using chi-square statistics at 0.05 level of significance. The results indicated that the main sources of students’ study problems have strong influence on students’ study habit which is causally related to the performance and consequently the efficiency of the students during the practical lesson in volumetric analysis. Based on the findings of this study, it was recommended that chemistry teachers need proper exposure and orientation to some psychological study problems in order to understand students’ developmental and...
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...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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...CHEMISTRY 425 Analytical Chemistry II Dr. Petr Vanýsek, Instructor 07 POTENTIOMETRIC TITRATIONS OF CHLORIDE AND IODIDE In this experiment the concentrations of chloride and of iodide in an unknown solution will be determined by volumetric titration with standard solution of silver nitrate using potentiometric indication. The potential of a silver electrode immersed in the solution is measured with respect to a reference electrode. In this experiment a glass electrode will serve as a reference electrode, since the pH of the solution is invariant during the titration. The position of the titration curve with respect to the volume axis does not depend on any knowledge of the electrode potential for either the measuring electrode or the reference electrode. The data obtained also enable calculation of the solubility (solubility product) of AgCl and AgI. AgI (ca. Ksp = 1x10-16) precipitates first since it is less soluble than AgCl (ca. Ksp = 1x10-10). Silver chloride starts precipitation near the equivalence point of the iodide titration. The potential rise* of the iodide titration curve will level off at the point when the chloride starts precipitating, that is near the iodide equivalence point inflection. This will be followed by a typical S-shaped chloride potentiometric end point. The error in determining the iodide end point is small if it is taken at the point at which the potential levels off. [* Depending on the manner in which the reference and working electrodes are...
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...12.097 Environmental Chemistry of Boston Harbor – IAP 2006 Lab 1: DETERMINATION OF DISSOLVED OXYGEN BY WINKLER TITRATION 1. Background Knowledge of the dissolved oxygen (O2) concentration in seawater is often necessary in environmental and marine science. It may be used by physical oceanographers to study water masses in the ocean. It provides the marine biologist with a means of measuring primary production - particularly in laboratory cultures. For the marine chemist, it provides a measure of the redox potential of the water column. The concentration of dissolved oxygen can be readily, and accurately, measured by the method originally developed by Winkler in 1888 (Ber. Deutsch Chem. Gos., 21, 2843). Dissolved oxygen can also be determined with precision using oxygen sensitive electrodes; such electrodes require frequent standardization with waters containing known concentrations of oxygen. They are particularly useful in polluted waters where oxygen concentrations may be quite high. In addition, their sensitivity can be exploited in environments with rapidly-changing oxygen concentrations. However, electrodes are less reliable when oxygen concentrations are very low. For these reasons, the Winkler titration is often employed for accurate determination of oxygen concentrations in aqueous samples. 2. Scope and field of application This procedure describes a method for the determination of dissolved oxygen in aqueous samples, expressed as mL O2 (L water)...
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...An Oxidation-Reduction Titration: The Reaction of Fe2+ and Ce4+ LAB ADV COMP 8 From Advanced Chemistry with Vernier, Vernier Software & Technology, 2004 INTRODUCTION A titration, as you recall, is a convenient method of learning more about a solution by reacting it with a second solution of known molar concentration. There are a number of ways to measure the progress of a titration. The method used in this experiment is called a potentiometric titration, in which the electric potential of a reaction is monitored. All acid-base titrations that are measured by a pH probe are potentiometric; thus, this method is not as unusual as it may seem. You will conduct an oxidation-reduction reaction in this experiment in order to determine the amount of iron (II) ions in a solid sample of ferrous ammonium sulfate hexahydrate, (NH4)2Fe(SO4)2•6H2O. The oxidizing agent for the sample will be ammonium cerium (IV) nitrate, (NH4)2Ce(NO3)6. The net ionic equation for the reaction is shown below. Ce4+ (aq) + Fe2+ (aq) → Ce3+ (aq) + Fe3+ (aq) This experiment illustrates the electrical nature of chemical reactions, and offers practice with a process for observing and measuring an oxidation-reduction reaction. OBJECTIVES In this experiment, you will • Conduct the potentiometric titration of the reaction between ferrous ammonium sulfate hexahydrate and ammonium cerium (IV) nitrate. • Measure the potential change of the reaction. • Determine the molar concentration of iron (II) ions in...
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...Titration Analysis of Commercial Bleach Introduction In order to determine the percentage of sodium hypochlorite in two different commercial bleaches and compare the relative effectiveness of the two bleaches a titration procedure will be used. Titration is a procedure for determining an unknown concentration of a solute using a reaction with a second solution with a known concentration. Commercial bleaches contain sodium hypochlorite. This is the active ingredient. In experiment 7 we demonstrated the ability to do a titration procedure to determine the sodium hypochlorite percentage in two commercial bleaches. Once we figured the two percentages we compared them to see which was the strongest. To determine the amount of NaClO in each solution we had to perform two successive oxidation reduction reactions. For the experiment to have been successful NaClO(aq)+2NaI(aq)+2HC2H3O2(aq)→I2(aq)+NaCl(aq)+2NaC2H3O2(aq)+H2O(l) needed to become colorless shown as: I2(aq)+2Na2S2O3(aq)→Na2S4O6(aq)+2NaI(aq). Before beginning, we thought the second bleach would be stronger. Methods and Materials 1. First, we gathered all of the materials, which included: * Buret Clamp * Buret * Ring Stand * Small Funnel * Beaker for collecting waste materials * 125 mL Erlenmeyer flask 2. Then we rinsed the buret with 10 mL of 0.100 M sodium thiosulfate (Na2S2O3), using the small funnel, to clean the buret. The sodium thiosulfate was discarded into the waste beaker. 3. After...
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...SC155 - INTRO TO CHEMISTRY: MATTER AND EQUILIBRIUM Indigestion and Titration: An Acid-Base Titration Imagine yourself as the Lead Analytical Chemist at Kaplan Industries. Your first big assignment is to investigate the strength of several commercial antacids for the Food and Drug Administration (FDA). They have sent five antacids to be tested with a back-titration that works as follows: • • • First, each antacid tablet is mixed with 40 mL of 0.1 M HCl—this acidic solution is the same stuff that is in stomach acid, and one antacid pill is nowhere near enough to neutralize all 40 mL of the acid. So, to see how much extra help each antacid pill needs to neutralize 40 mL of 0.1 M HCL, you add 0.05 M NaOH drop-by-drop to back-titrate the solution until the pH is neutral. What this means is that, the stronger the antacid tablet, the less NaOH it will take to help bring the acid to neutral. (In other words, the stronger antacid tablets counteract more of the original HCl, leaving the solution closer to neutral before the NaOH is added.) Here are your results: Maalox Mass of one dose antacid mL NaOH used in backtitration 20.0 g Tums 21.0 g Mylanta 18.0 g CVS brand 18.3 g Rennies 17.5 g 24.1 mL 22.4 mL 20.0 mL 19.9 mL 24.4 mL 1. Which is the strongest antacid, on a single-dose basis? Which is the weakest? Explain and show your calculations. 2. Which are the strongest and weakest, on a by-weight (mass) basis? 3. When people do back titrations, they usually watch...
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...NATIONAL QUALIFICATIONS CURRICULUM SUPPORT Chemistry A Practical Guide Support Materials [REVISED ADVANCED HIGHER] [pic] The Scottish Qualifications Authority regularly reviews the arrangements for National Qualifications. Users of all NQ support materials, whether published by Education Scotland or others, are reminded that it is their responsibility to check that the support materials correspond to the requirements of the current arrangements. Acknowledgement © Crown copyright 2012. You may re-use this information (excluding logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/ or e-mail: psi@nationalarchives.gsi.gov.uk. Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned. Any enquiries regarding this document/publication should be sent to us at enquiries@educationscotland.gov.uk. This document is also available from our website at www.educationscotland.gov.uk. Contents Introduction 5 Chemical analysis 6 Qualitative and quantitative analysis 6 Volumetric analysis 6 Gravimetric analysis 14 Colorimetric analysis 17 Organic techniques 22 Introduction 22 Preparation 22 Isolation 24 Purification 29 Identification 33 Percentage yield 37 Errors 39 Accuracy and precision 39 Repeatability and reproducibility...
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...Table of Contents Abstract 1 Introduction 1 Experimental Method 2 Results 5 Discussion 8 References 8 Appendix 9 Chemical Equilibrium in Solution Ginger Rimestad 10 December 2005 Abstract The experiment, Chemical Equilibrium in Solution, makes use of a titration of a heterogeneous solution. This is done in order to find the distribution of molecular Iodine, I2, as the solute between two immiscible liquid phases, water and a hexane solution. The average values obtained for (I2) = 6.11E-06 M, (I-) = 0.1097, (I3-) = 2.82E-04. The results that were found in this experiment show an inaccuracy. This may have been due to the third run in the titration of the Iodine in Hexanes. This inaccuracy is represented on the graph. There should be no variation with the concentration shown. Unfortunately, due to there being only three trials completed there can be no certainty as to which trail is the least inaccurate. I. Introduction The purpose of this experiment was to measure the chemical equilibrium in solution of a typical homogeneous equilibrium in aqueous solution. The equilibrium that is to be observed is that which occurs when Iodine, I2, is dissolved in aqueous potassium iodide (KI). The equilibrium constant, Kc, for each run was found using; Kc = (I3-) (I2w) (I-) (1) The method involves the use of two immiscible liquid phases, aqueous and hexane solution...
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