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Determination Of An Unknown Concentration Of Vinegar Essay

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An investigation was conducted to determine an unknown concentration of ethanoic acid in various types of vinegar. Vinegar is a liquid that consists of around 4-8% ethanoic acid (CH3OOH), water and other trace chemicals (Wikipedia, 2018). The vinegars used in this experiment were wine, white wine and apple cider and they have 6%, 5% and 4% ethanoic acid concentrations respectively (University of Sydney, n.d). Vinegar is produced by the fermentation of ethanol by acetic acid bacteria. An acid is considered strong if they completely ionise in water to produce hydrogen ions and have a low pH, an example of a strong acid is hydrochloric acid (HCl). Weak acids, however, do not fully ionise and instead form an equilibrium mixture. Ethanoic acid …show more content…

Sodium hydroxide (NaOH) is an example of a strong base and is what was used in this experiment. A weak base does not fully ionise and in aqueous solutions, reacts incompletely with water to yield hydroxide ions (lumenlearning, n.d).
The solution with the unknown concentration but known volume (vinegar) is called an analyte and a solution with a known concentration (sodium hydroxide) is called the titrant. In titration, the titrant is added to the analyte to achieve the equivalence point and determine the concentration of the analyte. In this experiment, the ethanoic acid was combined with sodium hydroxide to produce a neutralisation reaction. This can be seen in equation 2.
Equation 2: Neutralisation reaction between vinegar and sodium hydroxide
CH3COOH(aq) + NaOH(aq)==> CH3COONa(aq) + …show more content…

It occurs when enough base is added for a neutralisation reaction to occur. The equivalence point between a weak acid and a strong base is pH 8.72. It must be attained precisely to produce accurate results. This is done by slowly adding the titrant to the analyte. The end point of the experiment refers to the point at which the indicator changes colour because of an indicator. The indicator phenolphthalein has a pH range of 8.2 to 10.0 and is used to determine the endpoint as it shows when enough of the base has been added to fully react with the acid. It remains colourless in an acid and when neutral, however, when the solution becomes basic, it turns pink. When it turns a pale pink, the endpoint has been reached and the amount of base can be determined, and the concentration of acid can be found. However, if the solution is overly titrated, it will turn a bright pink. This means that the results are no longer precise nor accurate. When the endpoint has been reached, the amount of base used can be determined, and thus the concentration of the acid can be found using

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