Determination of Vitamin C Concentration in Processed Fruit Drink

Title: Determination of Vitamin C concentration in processed fruit drink

Aim:

To determine the vitamin c content of a sample of processed fruit drink

Principle:

Vitamin C(ascorbic acid) is a kind reducing agent of which number of moles can be determined by titration with an oxidizing agent. Using iodine solution,

Knowing number of moles of iodine solution used, the number of moles and molarity of ascorbic acid can be calculated. Calculating the molarity of vitamin C of fruit juice stated on the labels, we can compare if it is true.

Chemicals and Apparatus:

140 ml fruit juice (containing 1000mg vitamin C) Measuring cylinders

100 ml sulphuric acid (1M) Beakers(500 ,250 ,100 )

30 ml potassium iodate(V) (0.05 M) Filter funnel

20 ml potassium iodide (1M) Pipette (25.0 , 5.0 )

10 drops of starch solution Pipette filler

Burette Conical Flasks

250.0 volumetric flask Clamp

Stand Droppers

Glass rod 3 transfer pipettes

Procedure:

A. Dilution of fruit juice

1. Rinse pipette(25.0 ) with distilled water and then with fruit juice

2. pipette 25.0 of fruit juice to a 250.0 volumetric flask

3. Add distilled water in wash bottle to the 250.0 volumetric flask until the graduation mark. Use dropper for the final drops of distilled water.

4. Stopper the flask and turn it upside down to mix the solution evenly.

B. Standardization of iodine solution

1. Use a 3 transfer pipette to transfer 15 of KI solution to a clean 100 beaker accurately.

2. Use another 3 transfer pipette to transfer 8 of solution to same beaker accurately.

3. Use another 3 transfer pipette to transfer 5 of solution to same beaker accurately. The solution will react with KI solution in acidic medium, forming iodine solution ( ) with total volume of 28 . (The molarity of solution can be calculated.)Then, use the solution in titration immediately. The reaction can be concluded by the following equation:

C. Titration

1. Rinse the pipette with distilled water and then with diluted fruit juice in (b).

2. Pipette 25.0 of diluted fruit juice to a clean conical flask

3. Add 2 drops of starch solution into the conical flask

4. Rinse burette with distilled water and standardized iodine solution

5. Fill the burette with standardized iodine solution with a filter funnel

6. Record the initial reading of burette

7. Run the iodine solution from the burette until dark blue color appears in the conical flask

8. Record the final reading of the burette

9. Repeat steps 6 to 9 for at least 3 times to get a more accurate result

Tables summarizing titration results:

Table 1:Titration of against fruit juice

1st Trial 2nd Trial 3rd Trial 4th Trial

Initial burette reading ( )

24.4 21.5 17.9 14.3

Final burette reading( )

21.5 17.9 14.3 10.6

Volume of used( )

2.9 3.6 3.6 3.7

Conclusion:

The molarity of the fruit juice calculated from the experimental data is M. The molartiy of the fruit juice calculated from the data on the labels of the drink is M.So it can be concluded that

Precaution:

1. Do not touch chemicals with bare hands

2. Dilute sulphuric acid is corrosive

3. Iodine solution should be used in titration immediately after standardization because it is unstable.

4. Label

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