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Analysis of sulphur dioxide content in wine.doc

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Introduction

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 SO2 molecules is first convert into SO32- by NaOH solution: SO2 + 2OH- � SO32- + H2O Acidification of the solution liberates all SO2: 2SO32- + 2H+ � 2SO2 + 4H2O which is then titrated with 0.0057M iodine solution in which starch is used as end-point indicator: SO2 + I2 + 2H2O � 2HI + H2SO4 Chemicals white wine (carbonated), 1M NaOH, 2M H2SO4, 0.0057M I2, 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 25cm3 of white wine into a conical flask. 3.> Add about 12cm3 of 1M NaOH and stand for about 15 minutes. 4.> Add about 10cm3 of 2M H2SO4 to the mixture and then few drops of starch solution as indicator. ...read more.

Middle

Even small amount of air, over a period of time, can adversely affect the wine. ~The need for wine additives~ Other than anti-oxidation, additives are added to wine to enhance its flavour and colour. The example are sugar, to reduce bitter taste of wine; ester, as flavouring agent to enhance flavour; sulphur dioxide, as antioxidant. Some wine which is needed to store for a long time especially need to preserve. Since dilute ethanol in wine can prevent bacterial growth, anti- oxidation is thus more important in preservation of wine. ~Safety of using wine additives~ No additives may be used unless it has been extensively tested on animals. Considerable research has been carried out in order to observe whether the additives affect growth, reproduction, or prevalence of cancer. These data are then used by experts to assess the risks to humans in using the additives. ~Sulphur dioxide as antioxidant~ Sulphur dioxide, including its salts, namely, sulphites (SO32-) and bisulphites (HSO3-) can preferentially react with atmospheric oxygen into harmless SO42-, thus prevent oxidation of wine. ...read more.

Conclusion

~Result~ By the experiment, SO2 content in wine is 44.88 mgdm-3 which is much lower than the limit of 450 mgdm-3 stated. However, this value is supposed to be not accurate since in this experiment, carbonated wine is used, and the carbon dioxide evolves will affect the measurement by pipette and can draw away the free sulphur dioxide in wine. So, non-carbonated white wine should be use (since colour may affect the detection of end-point). Although a bottle of wine doesn't exceed the limit of 450 mgdm-3, the heavy drinking of alcohol can damage heart, kidney, liver and central nervous system. Other than as antioxidant in wine, SO2 is also widely used in bleaching industry, Contact Process in manufacturing sulphuric acid and disinfectant. Conclusion Sulphur dioxide is used in wine as antioxidant. However, due to its toxicity and allergy to asthma patient, the limit of using sulphur dioxide must be set. ?? ?? ?? ?? ...read more.

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Response to the question

This piece covers all necessary aspects such as experimental data, discussion and conclusion to varying degrees of depth and better consistency would improve its grade. Overall the candidate sets out their calculations concisely but perhaps more detailed explanation of the ...

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Response to the question

This piece covers all necessary aspects such as experimental data, discussion and conclusion to varying degrees of depth and better consistency would improve its grade. Overall the candidate sets out their calculations concisely but perhaps more detailed explanation of the steps of the calculation would make their work easier to understand, it is important that coursework is clear at all times so that examiners know where to award marks. The conclusion needs to answer the question and recap the main points in detail which is not done here.

Level of analysis

In order to achieve top grades the candidate would need to match the detail found in their discussion, which incorporates evidence of additional reading and thorough discussion of the use of sulphites in wine and the reason for doing so. The areas labelled precautions and possible error would need to be expanded and more detailed analysis provided for both. It would be wise to include health and safety notes at this level of study and more specific details about the experimental procedure and possible variables would ensure the experiment was as reliable as possible. Always imagine you are explaining the procedure to someone who has never carried it out before and ask yourself what they would need to know to repeat it as exactly as possible. The conclusion is not that of an A level student and should include evaluation of the analysis and link this to the real life implications mentioned in the discussion e.g. health problems.

Quality of writing

Some errors are present in terms of grammatical constructions which make the coursework difficult to understand and as a consequence prevent its fluency. Proofreading any work to ensure it makes sense is vital to achieve maximum communication marks.


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