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. Once all the ascorbic acid has been oxidized, the excess iodine reacts with a starch solution which was premixed with the ascorbic acid solution. It has several types like acid-base titrations and redox titrations. Give the overall equation for the reaction of vitamin C with iodine. Allow to cool and accurately weigh about 0.
This worksheet can also be downloaded from: All materials on this website are for the exclusive use of teachers and students at subscribing schools for the period of their subscription. Using the equation of the reaction between the iodate ions and iodide ions below calculate the moles of iodine formed. Once all the ascorbic acid has been oxidized, the iodine formed reacts with the starch solution to form the blue-black color that indicates the end of the experiment. The volume of iodine required to completely oxidize the ascorbic acid and bring about the change in color can now be used to determine the concentration of ascorbic acid in the solution. Each juice is labeled to contain 130% of the daily requirement of Vitamin C per serving 240mL.
Redox Titration Using Iodate Solution Safety Lab coats, safety glasses and enclosed footwear must be worn at all times in the laboratory. Wash the filter with a few milliliters of distilled water. Packing of whole fruits Volume of fruits needed m 3 of boxes we would have to take to provide a 75mg supply Lime 0. This causes a chemical reaction, in the process oxidizing ascorbic acid into dehydroascorbic acid and reducing the iodine to iodide ions. It is necessary part of the diet as it is required to form the protein, collagen.
The blue-black color is the endpoint of the titration. Vitamin C ascorbic acid is an antioxidant that is essential for human nutrition. The titration can be performed using just iodine solution and not iodate, but the iodate solution is more stable and gives a more accurate result. Calculate the amount of vitamin C in the 10. The reduced substance is causing oxidation and therefore called an oxidizing agent.
Would these errors lead to an overestimation or an underestimation of the Vitamin C content? Vitamin C deficiency can lead to a disease called scurvy, which is characterized by abnormalities in the bones and teeth. Furthermore, to make the example more comparable I assumed we would also fill the juice into those boxes. The basics of food titration involve determining the concentrations of different compounds in foods such as vitamins, minerals and trace elements. Blank titration is used to estimate the titration error. Read number of moles and mass of ascorbic acid in the titrated sample in the output frame. One way to determine the amount of vitamin C in food is to use a redox titration. Those data also show that taking the fruit juice of oranges would be the best option since it would require the smallest number of boxes we would have to store on the ship Table 6.
Vitamin C has the formula C 6H 8O 6 and can be oxidised to form C 6H 6O 6. Iodine will continue to be reduced into iodide ions as long as ascorbic acid is still present in the solution. Cholesterol in pork, sugar in a soda, carbohydrates in a cup of rice and alcohol in liquor. This is called an iodometric titration. To learn the concept and technique of redox titration. This method can be used to determine vitamin C concentrations in , fresh or packaged fruit juices and other foods such as vegetables and fruits.
Based on the concentration of iodine iodine we were able to determine by the standardization of the iodine solution we were able to calculate the concentration and mass and of ascorbic acid in the fruit juice Table 2. People always want to know the exact amount of things. Since the end-point of the titration is not observable, starch solution is added to act as an indicator since a complex of iodine and starch will form and lead to a dark blue colour. Since our laboratory time is limited each group only titrated the fruit juice of one fruit and the data for the other fruits was gained by collecting class data shown in Table 3. You will need to discuss its structure and explain why it is water-soluble as well as discuss the causes and effects of a lack of vitamin C in the diet. However this would not include the ascorbic acid need of the captain; this aspect is discussed in the final discussion section. 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.
To review oxidation-reduction reactions and their stoichiometry. Stir to dissolve and cool before using. So that means if we now consider the vitamin C content relative to the volume it turns out that using oranges would be the best fruits to take because their vitamin C concentration mass per unit volume is the highest and therefore we need to take less oranges which outweighs the disadvantage of their big volume. A student conducts the redox titration and reaches the endpoint after adding 25 mL of the titrant. Once all the ascorbic acid has been oxidised, the excess iodine is free to react with the starch indicator, forming the blue-black starch-iodine complex. That means if the concentration of vitamin c in the solution titrated with iodine solution the concentration of iodine we calculated might have been inaccurate. In this case oranges would also be the best fruits to take since the required number of boxes is the lowest in comparison to limes and lemons.
Based on this value, the volume of the fruit juice samples, the volume of the whole fruits and the concentration of ascorbic acid in our fruit juice samples I calculated the number of fruits we would have to take to cover the 75g need, as well as the overall weight and volume the fruits we would have to take would take. If the color fades, it means that ascorbic acid is probably being gradually released from something on which it is absorbed. Instead, a particular redox titration is used. It is this iodine, formed by the oxidation and reduction of iodide and iodate ions respectively, that oxidizes the ascorbic acid. We sometimes went 2 drops or 3 thinking it would reach the end point but sometimes we went over as evident by the color. Also the juice could easily goo bad and the vitamin c content in the juice would decrease due to oxygen oxidation of ascorbic acid.