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Investigation into vinegar

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Introduction

Investigation into vinegar Task The idea behind our investigation is to work out how much Ethanoic acid common vinegar contains. There are many reason which might determine the amount of acid in the vinegar. * How the vinegar was made. * The legal minimum. * What the vinegar was made from. The legal minimum for Ethanoic acid in vinegar is 4%. the amount of acid determines how much alcohol was present went it was distilled. This means that it is also determined by the amount of sugar that is there to start of with. SUGAR ==> ALCOHOL ==> Ethanoic ACID Set up We decided to use a titration to obtain our results. A titration is a fairly accurate way of doing this experiment. To work out how much Ethanoic acid is in the vinegar we are going to add NaOH (sodium hydroxide) to the vinegar (Ethanoic acid). Titration is the process of determining the quantity of a solution of a known concentration that will react completely with a certain amount of a sample being analysed. For solutions that react with each other, titration involves the addition of a known concentration to a solution of unknown concentration. We do this until the substances are completely reacted. The best example for titrations is an acid with an unknown concentration with a base. ...read more.

Middle

This suggested that we needed to change our experiment in some way. We then realised that by using a weaker concentration of NaOH (0.1 M) that it would take longer to change so the results would be more accurate. We also realised that we could add a certain amount of NaOH to the solution safe in the knowledge that it wouldn't meet the stoichiometric point. This speeded the whole experiment up. We also realised that the distilled malt vinegar had more Ethanoic acid. We believe that because it has been distilled, more sugar has turned to alcohol and therefore more alcohol has turned into Ethanoic acid. We know that NaOH is in a one to one reaction with the Ethanoic acid: NaOH + CH3COOH ==> CH3COONa + H2O This means the amount of NaOH is the same as the amount of acid. MaVa / MbVb = 1 This means we can write this as MaVa = MbVb Ma = 0.4 Va = 2.0 Mb = x Vb = 10 0.4 X 2.0 = 10x 0.8 = 10x 0.08 = x We then multiply this answer by 10 as the vinegars were diluted 10 times. This means that the amount of Ethanoic acid in the Dilute malt, according to our first test. 10(0.4 X 2.1) ...read more.

Conclusion

Cider, as an alcoholic drink contains roughly 3 % - 4 % alcohol. This is fairly low which explains why cider is at the bottom of the table. Red wine contains about 9% alcohol but can contain up to around 15%. This will explain why red wine is at the top of the table. White wine is normally slightly lower in alcoholic content than red wine. This is also reflected in the table. Experimental error In all experiments there are a number of experimental errors which could cause inaccurate results. One of the biggest mistakes could have been the reading of the amount of NaOH used. In the case above we can't tell where to take the reading from. The top of the reading is clearly at 1.05 but the bottom of the reading is nearer to 1.1. As a standard we always took the reading from the top of the curve. This could have happened at many points during the experiment. These points include * measuring out the 10 cm3 of vinegar. * Taking the reading form the burette. The NaOH was added in drops until the indicator changed colour. When we added the NaOH at the start we added it as a constant stream. When we were reaching the end of the titration we added it by drops. If the drops were added to quickly and the acid and the base hadn't reacted then it was possible that we added too much of the base. ?? ?? ?? ?? ...read more.

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