vitamin - Rose Croog I. Title: Determination of Vitamin C...

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Rose Croog I. Title: Determination of Vitamin C Concentration by Iodometric Titration II. Purpose: The goal of this lab is to determine the concentration of vitamin C in white cranberry juice and vitamin C tablets by a redox titration using iodine. III. Theory: Vitamin C, also known as ascorbic acid, with chemical formula C6H8O6 is an essential antioxidant and nutrient for human health. The two most widely known benefits of Vitamin C are in the prevention of scurvy, a condition characterized by defects in the bones and teeth, and in the treatment of colds and influenza. (Hot Exercise) i Many fruits and vegetables contain vitamin C, but cooking destroys the vitamin, so raw citrus fruits and their composite juices, and tablets are the main source of ascorbic acid for most people. Vitamin C is found in lemons, limes and other citrus fruits, tomatoes broccoli and other green leaf vegetables and bean sprouts. Because it is a water-soluble vitamin, any unused vitamin C is excreted. The minimum daily requirement is 30 mg, the recommended daily allowance is 60 mg . Since humans have no method of storage or synthesis of Vitamin C, daily consumption is a supplement is recommended for health and unless taken in excessive quantities, it is relatively harmless and reaps only benefits. As a consequence of the necessity of Vitamin C intake and our inability to store it, there is stress placed on its recommended daily allowance. When iodate ions (IO 3- ) are added to an acidic solution containing iodide ions (I - ), an oxidation- reduction reaction occurs. Iodate ions are reduced to form iodine: IO 3 - + 6 H + + 5 e - --> ½ I 2 + 3 H 2 O, while the iodide ions are oxidized to form iodine: 2 I - --> I 2 + 2 e - Combining these half-equations demonstrates the reaction between iodate and iodide: 2 IO 3 - + 10 I - + 12 H + --> 6 I 2 + 6 H 2 O.It is the iodine formed by this reaction that oxidizes the ascorbic acid to dehydroascorbic acid as the iodine is reduced to iodide ions: Ascorbic acid + I 2 --> 2 I - + Dehydroascorbic acid. Due to this reaction, the iodine formed is immediately reduced to iodide depending on the presence of any ascorbic acid. Once all the ascorbic acid has
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vitamin - Rose Croog I. Title: Determination of Vitamin C...

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