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The aim of the experiment is to determine the amount of sulphur dioxide in soft drinks. To ensure that the results achieved are obvious, 4 types of soft drinks, that are 100 Plus, Kickapoo Joy Joice, F&N Cool Ice Cream Soda and 7 Up were used in the experiment. The method used in the experiment is known as volumetric analysis. From the experiment, it is evident that SO2 is present in the four soft drinks used. 100 Plus contains second highest amount of free sulphur dioxide and lowest amount of total sulphur dioxide. Hopefully, this experiment will provide information and awareness of the effect of SO2 to the consumers’ health.
CONCLUSION
OBSERVATION:
Pipette 50 mL of sample into a conical flask
Pipette 25 mL of sample into a conical flask
Add 5 mL of 25% v/v sulphuric acid followed by 3 mL starch solution
Add about 25 mL of NaOH solution to the sample
Fill a burette with 0.01 M iodine solution
Shake the flask and leave it to stand for 15 minutes
Record the initial burette reading
Repeat steps for 3 times for each sample
Add 10 mL of 25% v/v sulphuric acid
Titrate the sample with iodine solution
Add 3 mL starch solution
Titrate the solution with iodine solution
Record the titre required to produce first appearance of deep blue colour
Record the titre required to produce the first appearnce of deep blue colour
PART 2: Determination of total SO2 in 100 Plus
Calculate the concentration of total SO2.
Volume of I2 used = 4.60 cm3
Number of Mole = MV / 1000
= 0.01 (4.60) / 1000
= 4.60 x 10-5 mol of iodine solution.
SO2 + I2 + 2H2O -------------> 4 H+ + SO4 2-+ 2 I-
1 mol of I2 ------------------>1 mol of SO2
4.60 x 10-5 mol of I2 ----------------> 4.60 x 10-5 mol of total SO2
.:. Amount (in mol) of total SO2 = 4.65 x 10-5 mol
20ml of 100 Plus used = 20ml / 1000
= 0.02 L
.:. Concentration of total SO2 = 4.60 x 10-5mol / 0.02 L
= 2.30 x 10-3 mol L-1
4.6 x 10-5 mol of total SO2 used.
Mole = Mass / RMM
4.6 x 10-5 mol = Mass (g) / 64.1 (RMM)
Mass(g) = 2.9486 x 10-3 g x 1000
Mass(mg) = 2.9486 mg
.:.Concentration of total SO2 = 2.9486 mg / 0.02 L
= 147.43 mgL-1
PART 1: Determination of free SO2 in 100 Plus
1) From the volume of iodine solution used, calculate the
amount (in mol) in 0.01 mol dm-3 iodine solution.
Number of Mole = MV/ 1000
= 0.01(4.65)/1000
= 4.65 x 10-5 mol of iodine
solution
2) Using an equation for the reaction, calculate the amount (in mol) of free SO2.
SO2 + I2 + 2H2O -------------> 4H+ + SO42- + 2I-
1 mol of I2 --------------------> 1 mol of SO2
4.65 x 10-5 mol of I2--------> 4.65 x 10-5 mol of free SO2
.:. Amount (in mol) of free SO2 = 4.65 x 10-5 mol
3) Calculate the concentration of free SO2 in the sample (in mol L-1).
Volume of 100 Plus used = 50 mL / 1000
= 0.05 L
Number of Mole of free SO2 = 4.65 x 10-5 mol
Concentration of free SO2 = 4.65 x 10-5 mol / 0.05 L
= 9.30 x 10-4 mol L-1
4) Express the concentration of free SO2 in mgL-1.
Number of Mole of free SO2 = 4.65 x 10-5 mol
RMM of free SO2 = 64.1
.:. 4.65x 10-5 = mass(g) / RMM (64.1)
Mass (g) = 2.98065 x 10-3 g
= 2.98065 x 10-3 g x (1000)
= 2.98065 mg
.:. Concentration of free SO2 = 2.98065 mg / 0.05 L
= 59.61 mgL-1 of free SO2
Table: Concentration of free SO2 and total SO2 in samples of soft drinks
METHODOLOGY
Part 1 : Determination of free SO2.
1. For 100 Plus, 4.90 cm3 of iodine was added in the 1st attempt and 4.40 cm3
of iodine was added in 2nd attempt before we see a change in colour.
2. For Kickapoo Joy Juice, 5.80 cm3 of iodine was added in the 1st try and 4.60
cm3 of iodine was added in the 2nd try.
3. In F&N Cool Ice Cream Soda, 5.00 cm3 and 3.30cm3 of iodine was added in 2
different attempts before colour changes in the sample used.
4. In 7 Up, 2.80 cm3 and 2.00 cm3 was required to change the colour of the
sample.
Part 2 : Determination of total SO2.
1. In 100 Plus, 4.10 cm3 and 5.10 cm3 of iodine was added in two different
attempts to achieve a colour change in sample.
2. For Kickapoo Joy Juice, 3.00 cm3 of iodine was added before colour changes in
the sample. 7.10 cm3 of iodine was needed in the next attempt.
3. For F&N Cool Ice Cream Soda, 5.70 cm3 and 8.50 cm3 of iodine was titrated
into sample before sample changes colour.
4. In 7 Up, 4.80 cm3 and 6.10 cm3 was added into sample to achieve a change in
colour of the sample.
Concentration
of Sulphur Dioxide (mgL-1)
7 Up
100 Plus
F&N Cool
Ice Cream Soda
Kickapoo
Joy Juice
Figure : Comparison between amount of free SO2 and total SO2 in
samples of soft drinks.