Determination of Vitamin C by Redox Titration with Iodine Vitamin C (ascorbic acid) is an antioxidant that is essential for human nutrition. Vitamin C deficiency can lead to a disease called scurvy‚ which is characterized by abnormalities in the bones and teeth. Many fruits and vegetables contain vitamin C‚ but cooking destroys the vitamin‚ so raw citrus fruits and their juices are the main source of ascorbic acid for most people. One way to determine the amount of vitamin C in food is to use a
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The Reaction:2 The reaction I am studying is often referred to as an iodine clock reaction.’ A clock reaction is where the time taken to form a definite‚ small amount of a product at the beginning of a reaction is recorded to work out the rate. This reaction involves the oxidation of iodide ions to iodine molecules which are soluble in water and are visible as a pale brown clear solution. The formation of the iodine can easily be detected because all other species in the reaction mixture are
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DISCUSSION Considered as moderately weak oxidizing agent‚ Iodine was used for the determination of strong reductants. Standard iodine solutions were found to have smaller electrode potentials as compared with the other oxidants‚ gaining them the advantage of imparting a degree of selectivity essential in the determination of strong reducing agents amid the presence of weak agents. Although regular re-standardization was essential for Iodine solution due to its lack of stability‚ it was still suitable
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IODINE TEST FOR STARCH The Iodine test is used to test for the presence of starch. Iodine solution — iodine dissolved in an aqueous solution of potassium iodide — reacts with the starch producing a purple black color. The colour can be detected visually with concentrations of iodine as low as 0.00002M at 20°C. However the intensity of the colour decreases with increasing temperature and with the presence of water-miscible‚ organic solvents such as ethanol. Also the test cannot be done at very low
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behind the Winkler method for DO analysis and (3) describe the sampling technique for the analysis of DO in water sample. In the Winkler method‚ or Iodometry‚ the dissolved oxygen is made to react with Iodide ion to yield Iodine which will be titrated afterwards with thiosulfate. Iodine is a moderately strong oxidizing agent making it useful for titrating strong reducing agents like dissolved oxygen. Iodide ion‚ on the other hand‚ is a weak reducing agent‚ and is the basis of determining the amount of
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almost perfect circle‚ takes longer to reach max expansion‚ covers more surface area‚ lays flatter on surfaceWater: did not form even circle‚ reached max expansion very quickly‚ formed more of a bubble on surfaceBOTH: Clear and shiny | e) Making iodine in water: potassium iodide (KI)‚ and sodium hypochlorite (bleach‚ NaClO). | KI- ClearNaOCl- ClearWhen combined they solution immediately turned a bright yellow. |
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drops of iodine solution to tube 5. (i) To the remaining liquid in tube 3‚ add about 20 mm Benedict’s solution and place the tube in the boiling water bath for 5 minutes. (j) Pour half the contents of tube 4 (starch and saliva) into tube 6 and then add three drops of iodine to tube 6. (k) Test the remaining liquid in tube 4 with Benedict’s solution as you did in (i). (l) Pour half the contents of tube 7 (starch solution) into tube 8 and test the two samples respectively with iodine as in
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) Ascorbic acid‚ C6H8O6‚ is a reducing agent that reacts rapidly with iodine (I2) in acidic medium to produce iodide ion (I-) and dehydroascorbic acid‚ as shown in the following equation: [IMAGE] + I2(aq) -----------> + 2H+(aq) + 2I-(aq) Ascorbic acid (Vit. C) Dehydroascorbic acid However‚ since iodine is only slightly soluble in water‚ ascorgic acid should not be titrated directly by a standard iodine solution‚ since the end point of titration is not o obvious. Instead‚
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gauze(OR 90oC electric water bath OR hot plate) * 250 cm3 beaker * boiling tube * anti- bumping granules * forceps * test tube holder * white tile * leaf to be tested (hibiscus leaves are excellent) * 90% ethanol * iodine/potassium iodide solution PROCEDURE: The video above shows the steps in Testing a Leaf for the Presence of Starch. The Procedure outlined below is slightly different. 1. Remove a green leaf fom a plant that has been exposed to sunlight for
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Lab report Aim : To check the presence of starch in the leaves Hypothesis : the presence of starch can be detected if the specimen turns black blue after iodine solution. Materials : 1) Green leaves 2) Wire gauze 3) Iodine solution 4) Forceps 5) Specula 6) Bunsen’s burner 7) Test tube 8) Water 9) Tile 10) tripod stand 11) glass 12) slide 13) dropper 14) water 15) water bath Procedure: collect dark green leaves (as leaves contain starch) take a water bath and let it heat
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