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Which fruit juice (Orange, Apple, Peach, Pineapple, and Apricot) has the highest concentration of ascorbic acid?

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Dafna Bicaci IB Chemistry SL Acids & Bases - Design Lab ASCORBID ACID CONTENT DESIGN LAB PURPOSE: Which fruit juice (Orange, Apple, Peach, Pineapple, and Apricot) has the highest concentration of ascorbic acid? VARIABLES: 1. Independent Variables: In this experiment, my independent variables are the different fruit juices; apple, apricot, peach, orange and pineapple. 2. Dependent Variables: The dependent variable in this experiment is the concentration of ascorbic acid the fruit juice contains which is calculated by the formula: , in this case, (Concentration(DCPIP) x Volume(DCPIP))/ Volume(Ascorbic Acid) = C(Ascorbic Acid) 3. Controlled Variables: 1. I will use the same brand of fruit juice for every trial 2. The juices will be diluted with 10 mL distilled water. 3. I will use 0.1 mol/dm3 of DCPIP for each trial. MATERIALS: 1. 30 mL each of ?Tamek? brand Apple Juice, Orange Juice, Pineapple Juice, Apricot Juice, and Peach Juice 2. Graduated cylinder 3. 100 milliliters of dichlorophenolindophenol (DCPIP) ...read more.


When acid and base react, the reactants are salt and water. The reaction in this experiment was 1:1. Therefore, to calculate the concentration of ascorbic acid in the juices, I use the formula below: . Calculated concentration of Ascorbic Acid (mol): Calculated Concentration of Ascorbic Acid (moldm3) APPLE 0.029±4.07% ORANGE 0.146±2.62% PEACH 0.027±3.54% PINEAPPLE 0.052±2.18% APRICOT 0.028±3.41% The table above shows the concentration of ascorbic acid of each fruit juice calculated from the volume of DCPIP, concentration of DCPIP and volume of ascorbic acid. It can be seen that they all have different concentrations of ascorbic acid however, they are very close to each other. An example of the procedure of calculating the concentration of ascorbic acid is below: APPLE JUICE TRIAL 1 TRIAL 2 TRIAL 3 Concentration of DCPIP 0.1 mol 0.1 mol 0.1 mol Volume of DCPIP 5.3 (±0.05) 4.2 (±0.05) 4.2 (±0.05) Volume of Ascorbic Acid 20 (±0.05) 20 (±0.05) 20(±0.05) Recorded values Apple Juice and DCPIP: Concentration of Ascorbic Acid = TRIAL 1ï Concentration of Ascorbic Acid = = 0.027 ±1.19% ...read more.


Evaluation: Limitations: This experiment was not done in a professional laboratory therefore there has been some limitations. First of all, the juices were kept in an open place therefore the concentration of ascorbic acid might have been oxidized in the air and therefore I might have recorded lower results as it should?ve been. Secondly, when fruit juice is dropped into test tube containing DCPIP solution, a suspension formed and its color slowly changes to black. The presence of the suspension in DCPIP solution makes it harder to determine whether DCPIP solution has been completely decolorizes. Another limitation would be that we considered there would only be ascorbic acid in the juices however, there might be other chemicals or different types of acid that has contributed to the neutralization process as well. Improvements: Since we did not work at a professional lab, there was no way to avoid oxidation of the ascorbic acid to the air. The only way to avoid that would working a little bit faster so there is less oxidation. In addition, using a colorimeter might help to determine completely colorization. This would help me by having results that are more accurate. ...read more.

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