Essay redox titration

942 Words Oct 24th, 2013 4 Pages
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 redox titration. The redox reaction is better than an acid-base titration since there are additional acids in a juice, but few of them interfere with the oxidation of ascorbic acid by iodine.
Iodine is relatively insoluble, but this can be
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Repeat the titration until you have at least three measurement that agree to within 0.1 ml.
Titrating Real Lemon
Real Lemon is nice to use because the maker lists vitamin C, so you can compare your value with the packaged value.
1. Add 10.00 ml of Real Lemon into a 125 ml Erlenmeyer flask.
2. Titrate until you have at least three measurements that agree within 0.1 ml of iodine solution.
Other Samples
• Vitamin C Tablet - Dissolve the tablet in ~100 ml distilled water. Add distilled water to make 200 ml of solution in a volumetric flask.
• Fresh Fruit Juice - Strain the juice through a coffee filter or cheese cloth to remove pulp and seeds, since they could get stuck in the glassware.
• Packaged Fruit Juice - This also may require straining.
• Fruits & Vegetables - Blend a 100 g sample with ~50 ml of distilled water. Strain the mixture. Wash the filter with a few milliliters of distilled water. Add distilled water to make a final solution of 100 ml in a volumetric flask.
Titrate these samples in the same way as the juice sample described above.
Titration Calculations
1. Calculate the ml of titrant used for each flask. Take the measurements you obtained and average them. average volume = total volume / number of trials
2. Determine how much titrant was required for your standard.
If you needed an average of 10.00 ml of iodine solution to react 0.250 grams of vitamin C, then you can determine how much vitamin C was in a

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