Lab: Determining the Quantity of Vitamin C in Fruit Juice A titration does not always have to involve an acid-base react

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Lab: Determining the Quantity of Vitamin C in Fruit Juice A titration does not always have to involve an acid-base reaction. Analyze the information provided about a titration to determine the concentration of vitamin C in fruit juice. Vitamin C, also called ascorbic acid, is commonly found in commercial fruit juices and drinks. In this activity you will analyze data collected from a titration analysis of a fruit juice. Nutrition Facts Valeur nutritive Calories Cate TH Fat/get Cholester bang Protein VA/ V C/ Path/ Potassium 200 mg 8% Carbabyste/ Chaldes 15 15 Thes/Plon 5g 45 A CO C 45 80% 45 IN OCTURNING TRUTSIGAn (2 Vitiman C (Ascorbic acid) H 0 H C-C-0-H A ! H H O-H molar mass 176.14 g/mol H-0 Background Information Ascorbic acid reacts with lodine in solution, as described by the following reaction: ascorbic acid(aq) +1,(aq)-dehydroascorbic acid(aq) + 21 (aq) In this procedure a standard aqueous iodine solution is added to a sample of juice. The initial reaction involves lodine reacting until the ascorbic acid in the juice sample depletes. The endpoint of this titration is a blue colour, signified by the reaction of excess iodine with starch (which is added to the juice prior to titration). Earlier in this lesson you calculated a mass of vitamin C (ascorbic acid) that you would expect to find in the juice if it met the 80% of the daily recommended amount. Purpose The purpose of this investigation is to test the manufacturer's claim that the juice product contains 80% of the daily recommended amount of ascorbic acid.
Problem What mass of vitamin C (ascorbic acid) is present in a box of juice? Materials • • • • • . . lab apron eye protection fruit juice (200-ml box) 0.002 00-mol/L iodine solution starch indicator solution distilled water 50-ml burette and stand stirring rod small funnel 10-mL volumetric pipette and bulb clean, dry beaker 125-ml. Erlenmeyer flask Procedure Step 1: Assemble the ring stand and burette clamp. Clean the burette using distilled water, and wash using a small quantity of the aqueous iodine solution. Place the burette in the clamp. Step 2: Fill the burette with the aqueous iodine solution. Step 3: Read and record the volume in the burette. Step 4: Clean the pipette using distilled water, and wash using a small quantity of the fruit juice. Use the pipette to transfer 10.00 mL of juice to the Erlenmeyer flask. Step 5: Add a few drops of the starch indicator solution to the Erlenmeyer flask. Step 6: Add 40 mL of distilled water to the Erlenmeyer flask Step 7: Titrate the juice sample to the desired endpoint-a permanent dark blue colour. Measure and record the burette reading at the endpoint. Record the endpoint colour. Step 8: Repeat steps 3 to 7 three more times (four trials altogether).
Observations 2. 3. Titration of 10.00 mL Fruit Juice with 2.00 x 10-3 mol/L 1,(aq) Trial Final Burette Reading (ml) Initial Burette Reading (mL) Volume of 1,(aq) Added (ml) Final Colour of Solution 1 11.08 0.05 11.03 purple 2 21.27 11.03 10.19 blue 3 31.50 21.27 10.23 blue 4 41.72 31.50 10.22 blue Use the data to calculate the average mass of ascorbic acid present in the titrated samples.(5 marks) The volume of juice tested was 10.00 ml. What amount of ascorbic acid would be ingested if the entire juice box (200 mL) were consumed? (1 mark)