Vitamin C Lab

 This is a Vitamin C lab completed.



Determining the Concentration Level of Vitamin C in
Different Juices

AISB 0714
Jan 7, 2013
(Graph and Data Table On Different Attachment)

Objective

To quantitatively test natural sources for vitamin C.

Materials

Flask (2)
25mL of control solution
1mL of 1% starch (for 6 trials)
50mL of IKI
Stirring rod
Baseline measurement
Burette
Apple juice, orange juice, grape juice, pineapple juice
7 beakers
Distilled water

Procedure

Read the entire procedure and create your own data table(s) to record your results
Obtain 25 ml of the control solutions and pour it into your flask
Add 1 ml of 1% starch solution to the juice in the flask
Add 50 ml IKI to the burette; note the initial volume and record it in your data table
(record the exact amount in the burette.)
Slowly the iodine solution to the solution in the flask, drop by drop, swirling the
liquid between each drop added, until the solution in the beaker turns a blue/black
color.
Note the volume of the iodine solution used to titrate the solution, and record it in
your data table.
Clean your beaker/flask.
Perform steps 3 to 6 for each test solution.
Clean up your lab station.
Using the baseline measurement, you will now be able to quantify the amount of
vitamin C in the other solutions.

Variables and Controls

Independent Variable: The type of solution used (juices). Different juices were used
in order to quantify the different concentrations of natural vitamin C within the
juices.

Dependent Variable: The final volume of solutions. The initial concentration within
the juices were altered from the IKI solution, which affected the final volume.

Control Variables: Maintain 25 ml of control solutions
Amount of IKI put in
The amount of

Data Presentation

Having known that 500 mg of vitamin C dissolves in 500 ml of water means there is
a concentration level of 1mg/ml. Concentrated liquid used up an average 8.5 ml of
lugols. The formula below was used to show the concentration level on Lemon juice:

1 mg/ml    8.5 ml
X mg/ml    0.7 ml
 
Example:
8.5=0.7 =0.7/8.5 = 0.0834 mg/ml

Calculations

Percent Change:
= (Change in volume/ Initial Volume)x100
Example:
(0.5/18.1)x100=2.76%

Change in Volume:
= Final Volume-Initial Volume= Change in Volume
Example:
18.6-18.1= 0.5

Average:
(0.6+0.1+0.1+2.6+0.4+0.2+0.8+1.5)/8= 0.79

Evaluation

Water was the factor to remove the juices from the beaker and could have
been left inside the beaker and damaged the results. This could have been
an affect because the amount of acid that had to be found could have been
ruined by the results of not cleaning the products well. Water was not a
potential product for this procedure.
Having air bubbles in the burette has affected the pace of IKI coming out and
could of influenced the results. The burette was needed to add the amount
of IKI needed into the flask of juices. The amount of IKI added into the flask
could have been over or under the amount needed.
Starch was a product to concluding the blue/black color in the juices. The
reaction could have been an affected if not enough was added in. The pipet
could have had air bubbles and not the full 1 ml that was needed could have
been added into the juices.
The result of the blue/black was determined by the amount of IKI that
was added and stopping it at the right time to swirl. If the product was not
swirled at the right time more IKI could have been added, there for adding to
much into the product. This could of influenced the results that were gotten
in the table.

Improvements

Improvements could have been made by taking care of the materials. The
materials that were used had just been washed then reused. Next time having
more flasks could be an improvement because then products are not mixed.
The air bubbles in the burette is a complicated product to create
improvements on. The air bubbles were made by not stopping the product
properly could of resulted in the air bubbles. Cleaning out the burette after
each trial could have been made to make sure the product was used new
each time.
Cleaning the pipet could have been done by washing it out with water then
weighing it to make sure the balance was the same as the original weigh
before any liquid was added.
Taking more breaks in adding the IKI could have been an improvement and
not letting the IKI leak out.

Conclusion

The IKI reacted with the ascorbic acid, which then gave off the starch a blue/
black color. The starch reacting with the IKI created this blue/black color and
varied from amount of ascorbic acid that was in the juices. The more acidic the
juice the more IKI needed to be present.