The lab consists in determining the vitamin C concentration in a solution by a redox titration using iodine. Vitamin C (ascorbic acid) is a water-soluble, essential oxidant that plays a vital role in the protection of the body from infections and disease it is acquired from primary fruits and vegetables. With the use of different materials as natural orange juice, Tampico (chemical orange juice) and other solutions that contain vitamin C we will find the amount of vitamin C in each of these concentrations with the help of iodine, and with that data we can compare the difference that exist between the solutions and get to a conclusion of how the amount of vitamin C changes in both types of solutions.
Independent variable: Orange juice and Tampico.
Dependent variable: Amount of vitamin C each sample contains.
Controlled variable: Used amount of iodine.
Uncontrolled variable: Time.
* 50 ml burette and stand
* 100 ml or 200 ml volumetric flask
* 20 ml pipette
* 10 ml and 100 ml graduated cylinders
* 250 ml Erlenmeyer flasks
* Iodine solution (0,005 mol/l)
* Starch Indicator solution (0,5%)
* Ascorbic acid standard (1mg/ml)
* Natural Orange juice
* Tampico orange juice
General safety rules:
Use a labcode always.
Pick up your hair.
Always have you hands and your materials clean.
Be careful to spill the solution of iodine, or any of the solutions used.
Make sure you use correctly the materials because this can alter your data.
Be careful with the materials, mostly the ones of glass.
1.Use the Erlenmeyer flask to mix 150 ml of water, 10 ml of natural orange juice and 10 ml of starch indicator.
2.After those solutions are mixed in the flask, start pouring little by little the iodine solution into the flask, while doing this mix the solution with the iodine until the hole solution start changing color to a purple grayish tone. Be careful with pouring too much iodine till the solution turns orange or a dark grey.
3. As you pour the iodine into the flask take note of how much iodine was in the bourete at the beginning and how much of iodine is left until you get the result searched for this experiment. Calculate the volume of iodine solution used by subtracting the ending and beginning volumes. The amount of iodine used will determine the vitamin C content of your solution.
4. Repeat the same process as many times as necessary to collect the enough amount of data collection.
5. Repeat the whole process but with the solution of Tampico (chemical orange juice), collect the data to compare with the results of the orange juice vitamin C.
Natural orange juice table
10 ml of orange juice + 150 ml of water + 10 ml starch solution
Number of trial Initial volume of iodine (g ± 0.1 g) Final volume of iodine (g ± 0.1 g) Total volume of used iodine
1 0,0 7,7 7,7
2 7,7 14,4 6,7
3 0,0 8,9 8,9
4 8,9 15,3 6,4
5 0,0 6,2 6,2
6 6,2 13 6,8
Tampico orange juice table
10 ml of Tampico orange juice + 150 ml of water + 10 ml starch solution
Number of trial Initial volume of iodine (ml ± 0.1 ml) Final volume of iodine (ml ± 0.1 ml) Total volume of used iodine
1 0,0 5,9 5,9
2 5,9 11,8 5,9
3 0,0 5,3 5,3
4 5,3 10,9 5
5 0,0 5,9 5,9
6 5,9 12,4 6,5
Concentration of the solution: 1 g/l
Volume of ascorbic acid used in the Erlenmeyer flask: 10 ml
Amount of vitamin C in standard: 1 g/1000ml × 10 ml = 0,01 g of vitamin C
Calculating the amount of Vitamin C in the natural orange juice by the form:
Amount of vitamin C in standard = Amount of vitamin C in sample
Volumeiodine standard Volumeiodine sample
Volumeiodine standard (average): 7,1
Volumeiodine sample (total volume of used iodine, trial 1): 7,7
Number of trial Amount of...
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