IntroductionThis is a PowerPoint that will explain my question thatwas submitted to the Google Science Fair. The project Ichose was from the Chemistry branch of Science. Itincluded iodine titration to find the amount of VitaminC in different Orange juices. The presentation will takeyou on a step by step guide through my chosenexperiment.
Question and HypothesisThe question chosen was : Which type of Orange juice(fresh or bottled) has the most Vitamin C and is mostcost-efficient.The hypothesis was that the freshly squeezed orangejuice will have more Vitamin C than the bottled one.Sadly the fresh juice is also more costly.
Apparatus needed Samples of two different kinds of orange juice: home-made fresh-squeezed (which means youll need to buy some oranges), premium not-from-concentrate juice (e.g. Cappy ® Tropicana® or Floridas Natural®), Juicer for extracting juice from oranges (manual or electric is fine) Cheesecloth Vitamin C tablets Distilled water Masking tape Permanent marker Small funnel (do not use for food after using it for chemistry) Iodine solution, use one of the following: Lugols iodine solution, 50 mL or iodine solution for starch test
Apparatus needed (continued) Soluble starch, 10 g 50 mL graduated cylinder 500 mL graduated cylinder 50 mL Ehrlenmeyer flask 50 mL buret Ring stand Buret clamp Plastic transfer pipettes (or eyedropper) for adding drops of starch indicator solution 1/4 teaspoon measuring spoon, or an electronic kitchen balance (accurate to 0.1 g) Glass jars for iodine (300 mL) and starch solutions
The Method The Lugol`s solution was diluted 1:10 in distilled water to make the iodine titration solution. 30ml of Lugol`s solution was poured into the 500ml cylinder Enough distilled water was added to until the total volume was 300ml The solution was stored in a dry, light protected place. A starch solution was made. It could be anything between 0.5%-1.0%, although it was not critical. With 1.0% add 1g of the soluble starch to 200ml of near-boiling water. Stir and dissolve, let cool. Leave in a dry, away from sunlight area. Make standard solutions of vitamin C. This will be used to standardize the iodine titrate. 250g of vitamin C were crushed and diluted in 100ml of distilled water. Distilled water was added until the total volume was 250ml. 25ml of Vitamin C standard solution were titrated. 20ml of standard vitamin C solution was measured. This was poured into a 50ml Ehrlenmeyer flask. 10 drops of Starch indicator solution were added. The 50ml buret was set up on the ringstand. The buret was filled with iodine titration solution using a funnel. The initial volume of solution in the buret was recorded. The Ehrlenmeyer flask was placed under the buret. The iodine titration solution was added drop by drop. The flask was swirled after each added drop. The titration was complete when the iodine titration solution created a blue-black color that lasted longer than 20 seconds. The final volume of iodine solution left in the buret was recorded. The amount of iodine titration solution needed to oxidize the Vitamin C was found by calculating the difference between the two volumes. The results should agree with about 0.1 ml.
The Method (continued) The fresh orange juice was prepared. The juice of two oranges was squeezed using a juicer. The orange juice was filtered of seeds and pulp using filter paper. The titration of the fresh orange juice. 20ml of fresh orange juice were measured. The juice was poured into an Ehrlenmeyer flask. 10 drops of indicator solution were added. The 50ml buret was set up on the ringstand. The buret was filled with the iodine titration solution. The initial volume of iodine solution was recorded. The Ehrlenmeyer flask was placed under the buret. The iodine titration solution was added drop by drop. After every addition of iodine solution the flask was swirled. The endpoint was reached when the juice changed to a brownish color. The final volume of the buret was recorded. The amount of iodine titration solution needed to oxidize the vitamin C was calculated by finding the difference between the two recorded volumes. The results should agree with about 0.1ml. The process above was repeated with each type of juice (fresh, bottled). The amount of vitamin C was calculated using a proportion (with made up numbers). It took an average of 8.5ml of iodine titration solution to titrate 20ml of 1mg/ml vitamin C standard solution. That meant 20mg of vitamin C in total. It took an average of 6.8ml of iodine solution to titrate 20ml of fresh orange juice. The amount of vitamin C in the orange juice was called X. X was found using the following equation: X = (6.8mg/ml) × (20mg) ÷ (8.5ml) = 16.0mg
Results and Calculations Type of juice Amount of Iodine Amount of juice used needed to titrate (ml) Vitamin C Solution 1.0 0.25 g Fresh Orange Juice 1.0 25ml Cappy Juice 2.45 25mlIt took 1.0ml of Iodine to titrate 0.25 g of Vitamin C.The Cappy juice took 2.45 ml of iodine to be titrated.So:1.0ml÷0.25g= 2.45÷X4X=2.45X=1.633 this is the amount of Vitamin C in the Cappy JuiceThis value can now be converted to g/Liter:1.633÷25=6.532g/LThe Fresh Juice took 1.0ml to be titrated and following the equation above:4X=1.0X=0.25 This is the amount of Vitamin C in the Fresh Orange JuiceThe value above can be converted into g/Liters0.25÷25= 10g/L of Vitamin C
ConclusionIn conclusion, the hypothesis was proven true. The freshorange juice had as much Vitamin C in it as the tabletsthat had been diluted in water. The fresh juice had 10g/Lof Vitamin C whilst the bottled juice only had 6.532 g/L.This shows that it is much healthier to drink freshlysqueezed orange juice than the bottled one. It also showsthat the bottled juice doesn`t put the exact amount ofVitamin C included onto the bottle. Sadly, the bottledjuice is much cheaper and thus, more bought.
Bibliography and Thanks Here is a list of all sources used in the experiment: http://www.sciencebuddies.org/science-fair- projects/project_ideas/Chem_p044.shtml?fave=no&isb=cmlkOj E0NDEwNDU5LHNpZDoxLHA6MQ&from=TSW – as the idea behind the project http://en.wikipedia.org/wiki/Titration and http://en.wikipedia.org/wiki/Stoichiometry were used to give explanations of unknown terms. Special Thanks to: My Science Teacher Ms. Holmes for supporting me in the experiment. My parents, for buying and making the juices. The Technician Mr. Szilard for helping me obtain all the items needed for the experiment.
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