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This article is a study on kinetics of degradation of ascorbic acid from different orange juices. The objective of this study is to to study the degradation of vitamin C in samples of three different types of orange juices within a period of 10 days. The materials used by the researcher are fresh juice, Pascual refrigerated orange juice, and Don Simón non-refrigerated orange juice. This experiment is carried out by labelling and keeping those three different types of juices separately in the fridges. Then , the measurements were taken every two days except for weekends. The experiment was carried out for 10 days and successfully obtained 5 order to determine the concentration of vitamin C in the orange juices, the researcher separated the procedure into two parts which are reagent manufacture and titration process. In reagent manufacture part, the researcher made iodine solution, vitamin C standard solution and 1% starch indicator. The iodine solution is made by using 5.005 grams of potassium iodide,KI ,0.303 grams of potassium iodate,KIO3, 200 ml of distilled water and 30 ml of sulphuric acid H2SO4. The vitamin C standard solution was produced by diluting 0.252 grams of vitamin C powder in distilled water to a final solution of 250 ml. The titration process was aimed to determine the quantity of iodine necessary to neutralize the juice. The researcher took the vitamin C solution as a control, so the standard vitamin C solution was been titrated by carrying out the same procedure as the samples. The researcher poured 20 ml of the sample and added 10 drops of starch solution into Erlenmeyer flask. After filling iodine solution into the burette, the titration started. The researcher reduced the random error by repeating the titration with a second sample. After getting the data, the researcher calculated the mean volumes and their respective errors.
Then, the researcher used cross multiplication to find out the mass of vitamin C in the samples.
After that, the grams were divided by the molecular mass of ascorbic acid, C6H8O6 (176 g mol-1) to abtain the number of moles of ascorbic acid in each sample.
To calculate the concentration of vitamin C in mol per litre, the number of mole of vitamin C was divided by the volume of the samples.
The researcher had drawn a few graphs for observation. From the graph of vitamin C concentration against time, it can be observed that the concentration of vitamin C decreases with time. Besides, it shown that the fresh juice had the lowest rate of degradation of vitamin C as compared with the other two. Observation from the graph showing the change of concentration in time can also tell us that the fresh juice does not contain the greatest amount of vitamin C but non-refrigerated does. Lastly the researcher made a few conclusions. All types of juices studied shows the degradation of vitamin C. Although the fresh juice does not contain the greatest amount of vitamin C initially, the vitamin C in fresh juice can last longer compared to the other two types of juices studied.

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