Vitamin c determination by iodine titration lab report

Anna-Marie Finger. CHEM Section September 14, Results and Discussion. In this experiment a solution containing ascorbic acid was titrated with an iodine solution in order to determine the concentration of ascorbic acid in limes, lemons and oranges eq 1.

The concentration of the ascorbic acid in the fruit samples could be determined by referring to values of a standardized iodine solution in our calculations. Finally, the central question of which fruit would be the best one to take on a 50 day long journey, where every member of the 20 sailor crew needs 75mg of ascorbic acid per day was answered with the help of calculations.

Those results are shown in Table 4. Ascorbic Acid Titration. Standardization of the Iodine Solution. In order to be able to determine the concentration of 1 in the fruit samples we needed to prepare a standardized iodine solution. Based on amount of ascorbic acid in our titrated solution as well as on the volume of iodine solution used to cause the color change we were able to determine the concentration of iodine in the iodine solution and the concentration of ascorbic acid in the ascorbic acid solution.

We repeated this titration and collected class data so that we could use the average values of our measurements for our calculations. This approach leads to a more reliable result than just using the values of one single titration since the impact on different errors on the measurements should be minimized. Results of those calculations are shown in Table 1.

Table 1. Trial 1. Trial 2. Mass of beaker. Molarity of ascorbic acid solution. Moles of ascorbic acid in 50mL solution. Initial buret reading I 2.

Final buret reading I 2. Volume iodine solution used. Molarity of iodine solution.Introduction to Analytical Chemistry: Laboratory. Iodine is a versatile redox reagent because its potential falls in the middle of the range of potentials observed in aqueous solutions. Thus in the presence of strong oxidants, such as dichromate, iodide is oxidized to iodine; in the presence of reducing agents, such as As IIIiodine is reduced to iodide. Solid I 2 is only slightly soluble in water, but in the presence of excess iodide it forms the soluble triiodide ionI 3 -and it is in this form that it is used for redox titrations.

Reducing agents are determined by direct titration with standard I 3. For the determination of oxidizing agents it is not feasible to titrate directly with standard iodide, because a high concentration of iodide is needed to form the I 3 - complex. Instead excess iodide is added to oxidizing agents, and the excess I 3 - formed is titrated with a standard solution of a reducing agent, thiosulfate, S 2 O 3 An advantage to all of these analyses is the ready availability of a specific indicator, starch.

I 3 - reacts with starch to form an intense blue color that is visible even at very low I 3 - concentrations. In direct titrations with I 3 - the endpoint is signaled by the appearance of the blue color when the first trace of I 3 - is produced after the equivalence point.

In titrations of triiodide with thiosulfate, the endpoint is signaled by the disappearance of the blue color. Care must be taken, however, to add the starch after most of the I 3 - has already reacted.

Lab Report Vit C Titration new

In the presence of large I 3 - concentrations a rather stable complex forms, and the blue color persists beyond the equivalence point. In this exercise you will determine the weight percent of ascorbic acid, Vitamin Cin Vitamin C tablets. The I 3 - will be generated in situ by adding a known volume of a standard iodate, IO 3 -solution to a solution of ascorbic acid and iodide.

The iodate oxidizes the iodide to form I 3 -which reacts in turn with the ascorbic acid. The excess I 3 - is titrated with a standard solution of S 2 O 3 From the moles of I 3 - produced, calculated from the volume of standard IO 3 - solution added, and the moles of excess I 3 -calculated from the volume of standard S 2 O 3 2- used, the moles of ascorbic acid can be calculated.

The concentration of the standard iodate solution can be calculated directly from the weight of KIO 3 used. The thiosulfate solution must be standardized. The standardization is carried out against the standard iodate solution. A known volume of the standard iodate solution is added to an excess of iodide, generating a known amount of I 3. The I 3 - is titrated with the S 2 O 3 2- to a starch endpoint. Care must be taken in preparing and storing thiosulfate solutions.

Although sodium thiosulfate solutions are resistant to air oxidation, they do tend to decompose to give sulfur and hydrogen sulfite ion. Variables that influence the rate of decomposition include pH, the presence of microorganisms, the presence of Cu II ions, and exposure to sunlight.

To minimize the need for restandardization of the thiosulfate solution, it will be prepared under reasonably sterile conditions, at a pH between 9 and 10, and stored in the dark. Lab Schedule. Contact Instructor. Determination of Ascorbic Acid by Redox Titration : Introduction Iodine is a versatile redox reagent because its potential falls in the middle of the range of potentials observed in aqueous solutions.

Redox Titration Animation.Authors: B. Kramer, V. Pultz and J. Vitamins are a group of small molecular compounds that are essential nutrients in many multi-cellular organisms, and humans in particular. And although many of the subsequently discovered vitamins were not amines, the name was retained. In this exercise you will be studying vitamin C, also known as ascorbic acid.

Figure 1. Structure of vitamin C ascorbic acid. Ascorbic acid C 6 H 8 O 6 is a water-soluble vitamin, whose structure is shown in Fig. Vitamin C is easily oxidized, and the majority of its functions in vivo rely on this property.

10: Vitamin C Analysis (Experiment)

Occasionally during respiration O 2 is incompletely reduced to superoxide ion O 2 — instead of being reduced completely to its -2 oxidation state as in H 2 O. Ascorbic acid can donate a hydrogen atom to a free radical, and thus stop these reactions from occuring. A vitamin C deficiency in humans results in the disease called scurvy, whose symptoms include hemorrhaging especially in the gumsjoint pain and exhaustion. Fruits, vegetables, and organ meats e. Since vitamin C is easily oxidized, storage and the cooking in air leads to the eventual oxidation of vitamin C by oxygen in the atmosphere.

In this exercise you are to develop a testable hypothesis concerning the amount of vitamin C in a sample, design a procedure to test your hypothesis and then execute your plan in the laboratory. You and your laboratory partner will need to develop this hypothesis and submit a one-page typed proposal, which must be approved by your instructor before you can begin work.

Include in your proposal a list of the samples that you will analyze you will supply the samples and outline any sample preparation that is not described in the experimental section of this exercise. If you need to analyze many samples, you may collaborate with another group in the laboratory submit one proposal and one report for everyone involved. Please remember that certain activities are not easily performed in the laboratory i.

Therefore, you may need to perform some sample preparations, such as cooking, before coming to the laboratory. Also remember that if you wish to look at the change in vitamin C over time then you must plan ahead to allow for this.

Some possible topics are given below, but you are not limited to this list creativity will be rewarded. In general, projects that seek to only measure the amount of vitamin C in two or more samples for example, comparing apple and orange juice will not be graded as highly because they have a weak hypothesis. The only restriction on your choice of topic is that your work may not involve vertebrate animals or any samples of human origin. The amount of vitamin C in a sample will be determined by redox titration using the reaction shown in Scheme 1 between ascorbic acid and 2, 6-dichloroindophenol DCIP.

To be a self-indicator a substance must be one color in the presence of excess analyte i. Scheme 1. In acidic solutions DCIP is red, but if ascorbic acid is present, it will be reduced to a colorless substance.

The solution will remain colorless as more DCIP is added until all of the ascorbic acid has reacted. As soon as the next drop of DCIP solution is added at the solution will be light red, due to the excess DCIP and the end point of the titration has been reached.

There are several limitations to this method that you must consider when you are designing and performing your experiment. First, the presence of particles as in fruit juice can interfere with your ability to see the end point, and so cloudy juices will need to be filtered first.

Second, when analyzing solid substances you will need to dissolve the vitamin C before you can perform the titration. This may require blending or crushing the material and it may also require the addition of known amounts of water to the material. And finally, red materials cannot be analyzed by this method because it is impossible to see the end point. There are several other things to consider as you design your experiment.

First, you will need to have an estimate of how much titrant DCIP will be used in your titration. To achieve the most precise and accurate results, it is preferable that you do not use more than one full buret 40 mL of your titrant DCIP for a single titration. Conversely, a sample that requires only a few milliliters of titrant to reach an endpoint can also have very imprecise results your instructor will not accept endpoints which occur with less than 1 mL of DCIP.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 improved by complexing the iodine with iodide to form triiodide:. As long as vitamin C is present in the solution, the triiodide is converted to the iodide ion very quickly. Howevever, when the all the vitamin C is oxidized, iodine and triiodide will be present, which react with starch to form a blue-black complex.

vitamin c determination by iodine titration lab report

The blue-black color is the endpoint of the titration. This titration procedure is appropriate for testing the amount of vitamin C in vitamin C tablets, juices, and fresh, frozen, or packaged fruits and vegetables.

The titration can be performed using just iodine solution and not iodate, but the iodate solution is more stable. The goal of this laboratory exercise is to determine the amount of vitamin C in samples, such as fruit juice. The first step is to prepare the solutions.

What matters is that you know the concentration of the solutions and the volumes that you use. Freyre You titrate samples exactly the same as you did your standard. Record the initial and final volume of iodine solution required to produce the color change at the endpoint.

Real Lemon is nice to use because the maker lists vitamin C, so you can compare your value with the packaged value. For a 25 ml juice sample, for example Leave a comment. You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Pengajar dan Penulis Independen, Penyayang Kucing, Karakter : Humoris tapi Gampang Tersinggung, Agak temperamental dan cepat emosi, Cepat memaafkan, Lebih suka menganalisa sebelum berkomentar, Bersahabat tapi gak suka dengan orang yang Lebay.

Suka makanan yang pedas.The objective of this experiment is to use a redox reaction titration to accurately determine the amount of vitamin C in a sample of lemon juice, orange juice, or grapefruit juice. Its molecular formula is C6H8O6; its molar mass is Ascorbic acid is found throughout the plant and animal kingdoms, occurring in citrus fruits, hip berries such as rose hipsfresh tea leaves, tomatoes, broccoli, other fruits and vegetables, paprika, and the adrenal cortex of oxen.

It can be obtained from any of these sources but was originally isolated from and identified in oxen. It was the first vitamin to be prepared in pure form. Ascorbic acid is a white solid that has a sharp, sour taste and dissolves in water. The pure compound is stable to air oxidation when dry, but when impure as it is in many natural forms it is readily oxidized when exposed to air and light. Vitamin C is a fairly strong reducing agent and decolorizes many dyes.

Its aqueous solutions are rapidly oxidized by air; this reaction is accelerated in basic solution and in the presence of iron and copper ions. The vitamin-C content of juices can decrease rapidly with time once the juice is exposed to air. Vitamin C is essential to humans. It is involved in the synthesis of collagen, which constitutes about one-third of the total protein in the human body. A deficiency of vitamin C results in a disease called scurvy, which is characterized by weakness, swollen joints, bleeding gums and loose teeth, and delayed healing of wounds.

Scurvy was common in sailors, who had no fresh fruits or vegetables for long periods. In James Lind found that scurvy could be avoided if sailors were provided citrus fruit. A quantity of 60 mg vitamin C per day is enough to prevent the disease, and this is the recommended daily dietary allowance RDA. Vitamin C is also involved in iron metabolism, and many believe that very large doses are effective in preventing or curing the common cold.

However, some recent studies do not support this hypothesis. At large doses vitamin C causes problems such as diarrhea and the induction of kidney stones.

vitamin c determination by iodine titration lab report

Titration Reactions Titrations can be completed on both Acid-base reaction and oxidation-reduction reaction systems. Both types of reactions occur rapidly in aqueous solution, the balanced equations for such reactions can be determined, and there exist techniques such as changes in color of indicators or the color of the reactants themselves for determining when the reactants have been mixed in stoichiometric ratios.Dima Mogannam kaibni Class: 11thsci.

BBC, AIM The aim of this research project is to determine the level of vitamin C present in various fruit juices, based on the ways that the fruit has been preserved. This includes.

vitamin c determination by iodine titration lab report

Vitamin C is essential for human health. It is an antioxidant scavenger and it is also vital for tissue maintenance and repair. For example, severe Vitamin C in a prolonged period can lead to scurvy. Vitamin C can be obtained from fruit, vegetables, and lab made Vitamin C tablets. Introduction Vitamin C ascorbic acid is an essential nutrient used for the creation of certain biological compounds and is naturally found in citrus fruits. Just about every manufacturing facility used quality control, including medicine, food, and cosmetics.

Vitamin C video help calculations on experiment 1

Quality control is used to determine if a product, like food contain what they say they do. For example, a company claiming to make healthy food may understate the amount of high fructose corn syrup sugar. To observe some properties of chemical reactions 2. To associate chemical properties with household products Background Information: 2 of 20 points Chemical changes are often accompanied by physical changes.

Three that you should not see in this lab are changes in temperature, presence of a flame, and evolution of light, as when as firefly glows. Three physical changes that. Describe the effect that baking heat had on the chicken leg bone. The heat made it more rough and less flexible and brittle.

Rickets is a disease where the bones are not formed completely in children due to a lack of Vitamin D. Does the heated or acid-soaked bone represent a child with rickets? Explain why. Yes, because the acid-soaked bone had the calcium broken down, which is similar to what happens to children with. They mix the pollen with saliva and nectar from each plant. They then deliver it to other flowers or take it back to the hive for food. Bee pollen contains all 22 elements that comprise the human network and a few others.

It contains vitamins, minerals, fatty acids, amino acids, and enzymes. Home Page Research vitamin C lab report. Measuring the Vitamin C content in a variety of fruit juices Background Information Vitamin C, also called ascorbic acid, is a water soluble vitamin. Variables Independent Variable — Type of fruit juice used fresh or …show more content…. The fact that they decolourised from their original colour was taken as proof that ascorbic acid was present. Data Processing Using this formula the concentration of ascorbic acid in all the liquids was found Volume of 0.Bubble www.

Very Nice explanation which i was unable to find properly on the other websites.

vitamin c determination by iodine titration lab report

Juice is a juice product obtained by physical means such as pressing, centrifuging, extraction, etc. Fruit juice is divided into clarified juice and turbid juice according to the form. Juice testing. Post a Comment. About me group 4 biochem View my complete profile. Practical no. Measuring Vitamin C using starch-iodine test Abstract :. In this experiment, the main objective is to measure the amount of vitamin C in many different types of foods such as fruits apples, honeydew, orange and papayavegetables white cabbage, brocolli and spinachand chrysanthemum flowers.

Honeydew has been chosen and the extraction of vitamin C was conducted in few different ways either freshly made, boil at high temperature or bake in oven. This various techniques gave different readings for the amount of vitamin C. The solution of vitamin C was tested with iodine solution in the presence of starch and hydrochloric acid HCl by using a titration method. Vitamin C is able to bind with iodine, thus as the vitamin C can no longer bind with the iodine all has been used upthe solution will turn into blue black solution.

Vitamin C - Ascorbic acid. 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. As long as vitamin C is present in the solution, the triiodide is converted to the iodide ion very quickly.

The blue-black color is the endpoint of the titration. This titration procedure is appropriate for testing the amount of vitamin C in vitamin C tablets, juices, and fresh, frozen, or packaged fruits and vegetables.

Food sources of vitamin C Honeydew. Hydrochloric acid HCl 1M, 5ml.


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