Exp' 16 Vitamin C Analysis p' 201

1
Exp. 16 Vitamin C Analysisp. 201

• Objective to determine the amount of vitamin C
  in a vitamin tablet, a fresh fruit, and a fresh
  vegetable sample.

2
Experiment 16 Introduction

• The human body does not synthesize vitamins and
  therefore must obtain them from our diet.
• Benefits of vitamin C
• Growth and development of teeth, gums, bones,
  cartilage, skin and blood vessels
• Anti-oxidant that helps protect against cancers,
  heart disease, and stress
• Helps the body absorb iron and folic acid

3
Experiment 16 Introduction

• It is more beneficial to consume sources of
  vitamin C raw because cooking leaches out the
  water-soluble vitamin.
• Some sources of vitamin C
• lt10mg/100g beets, carrots, eggs, milk
• 10-25mg/100g asparagus, cranberries, cucumber,
  lettuce, pineapple
• 25-100mg/100g brussels sprouts, citrus,
  tomatoes, spinach
• 100-350mg/100g chili peppers, sweet peppers,
  turnip greens, kiwi.

4
Experiment 16 Introduction

• Vitamin C is also called ascorbic acid

5
Experiment 16 Introduction

• In Part A youll prepare standard KIO3 and add
  excess I-. A sample of ascorbic acid is treated
  with a known amount of the solution.
• IO3-(aq) 5I-(aq) 6H(aq) ?
  3I2(aq) 3H2O(l)
• The ascorbic acid reduces some of the
  quantitative amount of I2 present.
• C6H8O6(aq) I2(aq) H2O(l) ? C6H8O7(aq)
  2I-(aq) 2H(aq)

6
Experiment 16 Introduction

• The remainder of the I2 is titrated with a
  standard S2O32- solution, producing colorless I-
  and S4O62- ions.
• (xs) I2(aq) 2 S2O32-(aq) ? 2 I-(aq)
  S4O62-(aq)
• Amount of ascorbic acid I2 (gen) I2 (xs)

7
Experiment 16 Procedure Notes

• First thing, prepare 600 mL of boiled, DI water.
• A.1. Prepare KIO3
• B.1. Will be prepared by stockroom.
• B.2-4. omit
• B.5. Fill a buret with the Na2S2O3 solution

8
Experiment 16 Procedure Notes

• C.1. Prepare a vitamin C tablet and go
  immediately to Part D for titration with the
  buret you prepared in Part B.
• C.2. Prepare a fruit juice sample and go
  immediately to Part D for titration with the
  buret you prepared in Part B.

9
Experiment 16 Questions

• Report Sheet questions 1 6