help me write conclusion of this lab:

1 EXPERIMENT Esperiments for General Organic and Biochemistry - Bettelheim/Landesberg Quantitative Analysis of Vitamin C Contained in Foods BACKGROUND Ascorbic acid is commonly known as vitamin C. It was one of the first vitamins that played a role in establishing the relationship between a disease and its prevention by proper diet. The disease scurdy has been known for ages, and a vivid description of it was given by Jacques Cartier, a 16th-century explorer of the American continent: "Some did lose their strength and could not stand on their feet.... Others ... had their skin spotted with spots of blood... their mouth became stinking, their gums so rotten that all the flesh did fall off." Prevention of scurvy can be obtained by eating fresh vegetables and fruits. The active ingredient in fruits and vegetables that helps to prevent scurvy is ascorbic acid. It is a powerful biological antioxidant (reducing agent). It helps to keep the iron in the enzyme, prolyl hydroxylase, in the reduced form and, thereby, it helps to maintain the enzyme activity. Prolyl hydroxylase is essential for the synthesis of normal collagen. In scurvy, the abnormal collagen causes skin lesions and broken blood vessels. Vitamin C cannot be synthesized in the human body and must be obtained from the diet leg,citrus fruits, broccoli, turip greens, sweet peppers, tomatoes) or by taking synthetic vitamin C (eg, vitamin C tablets, "high-C" drinks, and other vitamin C-fortified commercial foods). The minimum recommended adult daily requirement of vitamin C to prevent scurvy is 60 mg. Some people, among them the late Linus Pauling, twice Nobel Laureate, suggested that very large daily doses (250-10,000 mg) of vitamin C could help prevent the common cold, or at least lessen the symptoms for many individuals. No reliable medical data support this claim. At present, the human quantitative requirement for vitamin C is still controversial and requires further research. In this experiment, the amount of vitamin C is determined quantita- tively by titrating the test solution with a water-soluble form of iodine, 13: . - [1: II: triiodode ion) V (1) Expanded octets 1 2 ds en Ord shades Vitamin C is oxidized by ly as according to the following chemical reaction HO CH-CH OH HO-CH-CH2OH ory work int her O + 2HI -0 + 1 (2) H o OV wo nu: H OH OH be hi us i Jc Vium MW 254 Oxidured product MW 176 MW 174 As vitamin C is oxidized by iodine 1, becomes reduced to !" When the end point is reached (no vitamin C is left), the excess of l will react with a starch indicator to form a starch-lodine complex, which is blackish-blue in color 12 + starchiodine starch complex (blackish-blue) It is worthwhile to know that although vitamin C is very stable when dry, it is readily oxidized by air (oxygen) when in solution therefore, a solution of vitamin C should not be exposed to air for long periods. The amount of vitamin C can be calculated by using the following conversion factor 1 mL of 110.01 M) - 1.76 mg vitamin C 1 OBJECTIVE To determine the amount of vitamin C that is present in certain commercial food products by the titration method PROCEDURE Prior to this laboratory, there are techniques that you should revies. You will find the relevant techniques in the following experiments: (a) Use of the Spectrotine" pripet filler is in Experiment 2: (b) buret use and titration techniques are in Experiment 19 1. Pour about 60 mL of a fruit drink that you wish to analyze into a clean, dry 100-ml beaker. The fruit drink should be light colored, apple, orange, or grapefruit, but not dark colored, such as grape. Record the kind of drink on the Report Sheet (1). 2. If the fruit drink is cloudy or contains suspended particles, it can be clarified by the following procedure: Add Celite (about 0.5 g), used as a filter aid, to the fruit drink. After swirling it thoroughly, filter the solution through a glass funnel, bedded with a large piece of cotton. Collect the filtrate in a 50-ml Erlenmeyer flask (Figure 47.1). Experiment 1 untitative Arts Vitamin Contained in Fonds 3 3. Using a 10-ml volumetric pipet and a Spectroline pipet filler, transfer 10.00 mL of the fruit drink into a 125 ml. Erlenmeyer flask (sample 1). Then add 20 ml. of distilled water, 5 drops of 3 M HCI (as a catalyst), and 10 drops of 2% starch solution to the flask. CAUTIO Do not use your mouth to pipet. Use the Spectroline" pipet filler Cotton Grubu Figure 47.1 Clarification of fruit drinks 4. Clamp a clean, dry 50-ml. buret onto the buret stand. Rinse the buret twice with 5-ml. portions of iodine solution. Let the rinses run through the tip of the buret and discard them. Fill the buret slightly above the zero mark with a standardized iodine solution. (A dry funnel may be used for easy transfer.) Air bubbles should be removed by turning the stopcock several times to force the air bubbles out of the tip. Record the molarity of standardized iodine solution on the Report Sheet (2) Record the initial reading of standardized iodine solution to the nearest 0.02 mL on the Report Sheet (3a) 5. Place the flask that contains vitamin C sample 1 under the buret and add the iodine solution dropwise, while swirling, until the indicator just changes to dark blue. This color should persist for at least 20 sec. Record the final buret reading on the Report Sheet (3b). 6. Calculate the total volume of iodine solution required for the titration (3c), the weight of vitamin C in the sample (4), and the percent (w/v) of vitamin C in the drink (5) on the Report Sheet. 7. Repeat this titration procedure with two additional samples of the same fruit drink: (a) sample 2. a 20-ml portion; (b) sample 3, a 30-ml portion. Record the volumes of iodine solution that are required for each titration in the appropriate spaces on the Report Sheet Carry out the calculations as above. CHEMICALS AND EQUIPMENT 1. 50-ml buret 2. Buret clamp 3. Spectroline pipet filler 4. 10-ml volumetric pipet 5. 50-ml Erlenmeyer flask 6. Cotton 7. Filter aid 8. H-C apple drink 9. H-Corange drink 10. H-C grapefruit drink 11. 0.01 M iodine in potassium iodide 12. 3 M HCI 13. 2% starch solution Post-Lab Questions 1. Use the average concentration of vitamin C from your data, and calculate the volume of fruit drink that would satisfy your minimum daily requirement of vitamin C Show your work 63. 1 hung x 60mg .68 1 mg x = 88.IML 10om 68.1mg Nitamin C is ascorbic acid. If you examine the structure of ascorbic acid given in the Background action equation 2), there is no -COOH group gresent in the structure shown the ascorbic acis as concordiester, Write the equation for the hydrolysis (chewage by addition water of the lactone to the carboxythe acid to be- nettonic equation for the conversion of iodine, I, to lodide. What kind of reaction this 4. Refer to the Background section and examine the chemical reaction for the oxidation of ascorbic acid (equation 2). 2. What happened to the hydrogen atoms that were present in the scoris acid? During the redox thation of ascorbic add og alt for me, ascorbic acid 9s Oxldyzed to dehydroas cordc add. Simultaneously fodrne reduced b. Acid was added in the titration, but it is not present in equation (2) in a stoichiometric amount to So, what is the purpose of the acid? Dintny the course of the staction and In the form of hydrochlori (HCI) is added to the Pharon Hosk, However, in the final chemical equation it is seen that the acid is not present in a storchlometri ratto. The purpose of the aud is because the wid used acts as a catalyst, 5. The iodine for this experiment is in the form of 5, and not 1, Isee equation (1), Background section) Why is this form of iodine used? Because Podine is Wighly vokutile it makes its handling difficult. Due to ease of hinding and better solubility Sdine in this experiment is present in the form of trodde, 6. Condusin