redox titrations was essential. Acid-base titrations can also be used however they are not able to complete all of the reactions in the solution and do not interfere with the oxidation of ascorbic acid by iodine solution. Iodine is relatively insoluble‚ but this can be improved by complexing the iodine with iodide to form triiodide as the following formula suggests: I_(2(aq))+〖I^-〗_((aq))↔〖I^-〗_(3(aq)) This triiodide ion can be used to oxidize vitamin C to form dehydroascorbic acid. In this reaction
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HOW DOES THE SOLUBILITY OF POTASSIUM CHLORIDE (KCL) AND POTASSIUM IODIDE (KI) IN WATER VARY WITH TEMPERATURE? AIM To observe solubilities of KCl and KI with water at different temperatures To compare the two solubility curves and discuss what might vary the solubility of different ionic compounds. THE VARIABLES DEPENDENT VARIABLE Temperature INDEPENDENT VARIABLE Amount of solute (KCl‚ KI) CONSTANTS Amount of the solvent (water)‚ pressure APPARATUS 100G OF POTASSIUM CHLORIDE 100G
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By the end of this lab‚ the student should be able to: Identify the functional groups for each of the biomolecules that react in the following biochemical tests: Benedict’s test‚ Iodine test‚ Brown Bag test‚ Sudan III/IV test‚ and the Biuret’s Test. Describe the mechanism of reaction for: Benedict’s test‚ Iodine test‚ Sudan III/IV test‚ and the Biuret’s Test. Interpret the results when presented with data for each of the biochemical tests. Design experiments to identify biomolecules using
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In this practical‚ solutions of the 2 washing powders will be filled into 2 identical wells on the starch agar plate separately. Starch will be broken down by the amylase disused to the star-agar. A clean zone will be formed around the wells when iodine solution is added and flushed. The higher the amylase activity‚ the more the starch will be broken down. Hence‚ a larger and clearer zone will be observed. Thus the diameter of the clear zone can show the activity of the amylase. In this experiment
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for every trial. A 1% starch solution must be used in every test tube. Identical iodine solutions must be used to test the starch solution. The temperature of the warm bath water must be exactly 37 degrees C. Materials: Eyedropper Appoximately1 Liter of orange juice 25 test tubes One test subject for swishing the juice 25- 1% starch solutions (95 mL) Warm bath with water heated to 37 degrees C Iodine Stopwatch Litmus paper for pH testing Procedure: 1. Use an eye dropper to measure
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by titration between vitamin C (ascorbic acid) & iodine solution. Hence‚ compare this data with the manufacturer ’s specification. Principle In this analysis‚ certain amount of iodine solution‚ which is known in excess‚ is added to acidified ascorbic acid solution. Brown iodine can be easily reduced by acidified ascorbic acid to form colourless iodide ion: ← Equation I The excess iodine is then back titrated by standard sodium thiosulphate
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the unknown solution. The macromolecules being tested in this lab were carbohydrates (monosaccharides and polysaccharides) and proteins. To identify the presence of these macromolecules in a substance‚ three different tests were performed. Lugol ’s iodine solution was used for identification of starch and glycogen - polysaccharides - in the twelve solutions. A positive outcome of the test results in a colour change; blue-black in the presence of starch and a red-brown in the presence of glycogen. A
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Solution by Iodometric Titration Results and Discussion Oxidation-reduction titration is a kind of volumetric analysis where the titrant used undergoes a redox reaction with the analyte. In this experiment‚ the oxidation of iodide (I-) to produce iodine (I2) is taken into consideration. The use of this concept in a redox titration is called iodometry. Iodimetry‚ on the other hand‚ deals with the reduction of I2 into I-. Between these two methods‚ iodometry is more popular because it is more efficient
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blocks of thyroid hormones. Iodine is then needed for formation of the hormones by its absorption from the diet and then carried via bloodstream to the thyroid gland which is then secreted into the colloid and oxidised into iodine ions. The attachment of iodine ions to tyrosine molecules triggers the pairing process performed by the thyroid peroxidise. This leads to production of thyroxine hormone T4 (containing four iodine ions) and triiodothyronine T3 (containing three iodine ions). (Martini 2004)
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Iodine clock reaction This is the hydrogen peroxide/ potassium iodide ‘clock’ reaction. A solution of hydrogen peroxide is mixed with one containing potassium iodide‚ starch and sodium thiosulfate. After a few seconds the colourless mixture suddenly turns dark blue. This is one of a number of reactions loosely called the iodine clock. It can be used as an introduction to experiments on rates / kinetics. 63 Lesson organisation This demonstration can be used at secondary level as an introduction
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