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Vitamin C. I will investigate whether orange juice contains the most Vitamin C and how I can speed up and slow down the oxidation process of Ascorbic Acid.

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Introduction

Vitamin C in Fruit Juices Background: Ascorbic Acid, or more commonly known as Vitamin C, is a monosaccharide that has a five-membraned unsaturated ring with two hydroxyl groups attached to doubly bonded carbons. This feature means that Ascorbic Acid is readily oxidised to dehydroascorbic acid. This reaction is called oxidation because the Ascorbic Acid is loosing electrons. Ascorbic Acid deficiency leads to scurvy, a disease that shows weakness, small hemorrhages throughout the body that cause gums and skin to bleed, and loosening of the teeth. Vitamin C is a water soluble antioxidant, and plays a vital role in protecting the body. The body absorbs extra vitamin C in response to an infection. Because it is a water soluble vitamin, any unused vitamin C is excreted. The minimum daily requirement is 30 mg; the recommended daily allowance is 60-70 mg. C6H8O6 + C12H7NCl2O2 ----------> C6H6O6 + C12H9NCl2O2 The electrons lost from Ascorbic acid will be used to reduce one of my indicators Dichlorophenolindophenol(DCPIP), to DCPIPH and then to DCPIPH2. DCPIP (blue) + H+ ----------> DCPIPH (pink) DCPIPH (pink) ...read more.

Middle

Once I have diluted the DCPIP the risks are drastically reduced however I still need to wear goggles and a lab coat. Ascorbic Acid should be treated as an irritant and therefore I should wear goggles and a lab coat when handling it. I am using 5% Ethanoic acid however, it is not above 4 moles and therefore should be treated as an irritant just as DCPIP and Ascorbic Acid are. My solutions of Iodine will not be greater than 1M so they should be treated as an irritant not harmful and corrosive. I will always wear goggles and lab coats. When handling glassware I should be careful that none of it breaks, if it does I should ensure I do not touch the broken glass and seek help. Method Making up my Standard Solutions Ascorbic Acid- * Use the same scales throughout to ensure, if there is an error that it is the same error all the time. * Weigh out the mass of solid Ascorbic Acid (0.1g) by putting the solid in away from the balance so I do not spill any onto the balance, to make sure that I do not have less Ascorbic acid than I think I do. ...read more.

Conclusion

* Do a rough titration. * When doing your 5 real titrations, add starch to make determining the end point clearer. This is added near the end because if it is added at the start it can hold the ascorbic acid in a complex and the titration will not work properly. * Read off the titre at the bottom of the meniscus. * Repeat above procedures but for tropical juice and orange juice instead of Ascorbic Acid. The iodine solution, by reading the meniscus I can tell that this titre was 38.50 cm3 I found my Iodine titrations hard to do because they often formed big complexes with the Ascorbic Acid, preventing me to see the end point, so I will use DCPIP from now on. Investigating how to speed up and slow down oxidation After researching I found out that iron and copper ions can have an effect on the oxidizing ability of Ascorbic Acid. Copper Sulphate I added Copper Sulphate with Ascorbic Acid to see if that speeded up or slowed down its oxidation. Iron DCPIP http://www.chemistry-react.org/go/Faq/Faq_27690.html Ascorbic Acid http://wwwchem.csustan.edu/chem1112/1112vitc.htm DCPIP http://upload.wikimedia.org/wikipedia/commons/a/aa/DCPIP-reduction- 2D-skeletal.png DCPIP http://en.wikipedia.org/wiki/Dichlorophenolindophenol Hazcards http://moodle.colchsfc.ac.uk/mod/resource/view.php?inpopup=true&id=20361 ?? ?? ?? ?? Sam Hennessy The Sixth Form College, Colchester. Chemistry ...read more.

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