Orange Juice Experiment

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Register to read the introduction… In order to get precise quantitative data, I chose to use a titration method to find the ascorbic acid content in juices. The specific technique that I chose to use is the iodine solution method. Despite there being many other viable options to this titration process, I chose the iodine solution method because the color change is easiest to detect when using juices. The other tests are simple when using clear solutions, but on juices, the color change

000166-XXX 6 is not as apparent due to the colors of the juices, making it harder to get accurate results.
Other than iodine, one of the most commonly used titration solutions is the DCPIP. However, since DCPIP is an acid-base reaction, the other acids present in the juice (e.g. citric acid) may also interfere with this experiment and cause errors in the data (“Orange Juice Acid
Nutritional Facts”). Also, with limited resources in terms of getting DCPIP solutions, the iodine method ultimately became my most viable option.

Chemistry behind the titration process When iodine is added to the orange juice, the iodine undergoes a redox reaction
…show more content…
Ascorbic acid reduces the iodine and turns them into iodine ions (I-), while being changed into dehydroascorbic acid. The iodide ions then react with the hydrogen atoms from the ascorbic acid to form hydrogen iodide. This reaction can be explained through the following equation:
C6H8O6(aq) + I2(aq) à C6H6O6(aq) + 2HI(aq).
Once all the ascorbic acid has reacted, the excess iodine reacts with the starch in the solution, creating an iodine-starch complex that stains the solution to a dark blue color. Here, when no ascorbic acid remains to react with the iodine, the titration is said to have reached its endpoint.

Titration of Ascorbic Acid Solution In order to find the ascorbic acid content of orange juice, I needed a value of comparison.
Before calculating, I had used trial and error and tried 4 different concentrations (0.1M,
0.001M, 0.05M, and 0.005M), each of which had yielded inaccurate data. The calculations are as follows:

000166-XXX 7
100g of oranges ≈ 50mg of ascorbic acid (Fox & Cameron, 262). Now, assuming that 1g of orange makes 1 cm3 of orange juice, 1000cm3 of orange juice = 1000g of

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