Given: The following results were obtained when a sample of mango juice was anal

Question

Given: The following results were obtained when a sample of mango juice was analyzed to determine its vitamin C content. A 125.0 mL sample of the juice was placed in a flask with 20 mL of 0.5 M H2SO4, 2.0 g of potassium iodide, KI, and 40.00mL of 0.01782 M potassium iodate, KIO3. Titration with sodium thiosulfate required the use of 35.19mL of 0.09624 M Na2S2O3. Calculate the concentration of vitamin C in the juice sample in mg vitamin C per 100 mL juice.
Questions: 1.How many total millimoles of I3- are produced from the reaction between KI and KIO3?
2. How many millimoles of I3- are consumed from the reaction with thiosulfate ion?
3. How many millimoles of I3- reacted with the ascorbic acid in the juice?
4. How many milligrams of ascorbic acid were in the juice sample?
5. What is the concentration of Vitamin C in the juice sample expressed as mg Vitamin C per 100 mL of juice?


Given: The following results were obtained when a sample of mango juice was analyzed to determine its vitamin C content. A 125.0 mL sample of the juice was placed in a flask with 20 mL of 0.5 M H2SO4, 2.0 g of potassium iodide, KI, and 40.00mL of 0.01782 M potassium iodate, KIO3. Titration with sodium thiosulfate required the use of 35.19mL of 0.09624 M Na2S2O3. Calculate the concentration of vitamin C in the juice sample in mg vitamin C per 100 mL juice.
Questions: 1.How many total millimoles of I3- are produced from the reaction between KI and KIO3?
2. How many millimoles of I3- are consumed from the reaction with thiosulfate ion?
3. How many millimoles of I3- reacted with the ascorbic acid in the juice?
4. How many milligrams of ascorbic acid were in the juice sample?
5. What is the concentration of Vitamin C in the juice sample expressed as mg Vitamin C per 100 mL of juice?

Explanation / Answer

Determination of vitamin C in juice

1. moles of KI = 2/166 = 0.012 mol

moles of KIO3 = 0.01782 M x 40 ml = 0.7128 mol

mmoles of I3- produced = 3 x 0.7128 = 2.14 mol

2. mmoles of I3- consumed by Na2S2O3 = 0.09624 M x 35.19 ml/2 = 1.69 mmol

3. mmoles of I3- consumed by ascorbic acid in juice = 2.14 - 1.69 = 0.45 mmol

4. mg of ascorbic acid in juice = 0.45 mmol x 176 = 79.2 mg

5. concentration of ascorbic acid in the juice = 79.2/125 = 0.634 mg/ml

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