Analysis_of_sulphur_dioxide_content_in_wine_2

Analysis_of_sulphur_dioxide_content_in_wine_2 - Analysis of...

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Analysis of sulphur dioxide content in wine Objective To determine the amount of sulphur dioxide, an antioxidant, present in wine by using volumetric analysis. Principle All free SO 2 molecules is first convert into SO 3 2- by NaOH solution: SO 2 + 2OH - SO 3 2- + H 2 O Acidification of the solution liberates all SO 2 : 2SO 3 2- + 2H + 2SO 2 + 4H 2 O which is then titrated with 0.0057M iodine solution in which starch is used as end-point indicator: SO 2 + I 2 + 2H 2 O 2HI + H 2 SO 4 Chemicals white wine (carbonated), 1M NaOH, 2M H 2 SO 4 , 0.0057M I 2 , starch solution Apparatus volumetric apparatus, pipette, measuring cylinder, dropper, white tile Procedure 1.> Find out the volume of wine from the label on the bottle. 2.> Pipette 25cm 3 of white wine into a conical flask. 3.> Add about 12cm 3 of 1M NaOH and stand for about 15 minutes. 4.> Add about 10cm 3 of 2M H 2 SO 4 to the mixture and then few drops of starch solution as indicator. Quickly, titrate the mixture with 0.0057M iodine solution. 5.> Record the titre required to produce pale blue colour. 6.> Repeat steps 2-5 for 2-3 times. Data Analysis Trial 1st 2nd Final reading /cm 3 3.05 12.80 26.30 Initial reading /cm 3 0.25 9.70 23.25 Volume of I 2 added /cm 3 2.80 3.10 3.05
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Average volume of I 2 added /cm 3 3.075 Concentration of I 2 solution: 0.0057 M Volume of wine bottle: 750 cm 3 Number of moles of 0.0057M I 2 in the titre: (3.075)(0.0057) = 0.01753 mmol Number of moles of SO 2 in the 25cm 3 sample:
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Analysis_of_sulphur_dioxide_content_in_wine_2 - Analysis of...

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