The Process of Titration in Vinegar Acid Reaction

As vinegar is a common household ingredient to use in food and everyday life, I predicted that there would be around 5% ethanoic acid composition in vinegar. My hypothesis was not as strongly supported as it could have been, as the final percentage of ethanoic acid calculated in the experiment was a 2% higher. The higher the ethanoic acid in the vinegar, the more harmful it is to consume. For this reason, I concluded that there must have been several factors that resulted in the increased percentage. These will be discussed in the evaluation. Although my hypothesis was not strongly supported, it is known that Vinegar is produced by the oxidation of ethanol and table vinegar typically contains between 4 and 8 % v/v acetic acid (ethanoic acid). Meaning that my findings were very accurate in comparison to already known scientific studies. The bar graph constructed from my results shows a constant trend in the usage of sodium hydroxide in each trial. The volume of sodium hydroxide used is consistently around 30cm³, which presents how my trial each support one another. There were no major irregularities, which lead to the error bars calculated being very small. The standard error calculated for the results as a whole was around 0.1, which is hardly effective on the graph.

In regards to the method used for the experiment, phenolphthalein was the indicator used to observe neutralisation. Phenolphthalein is chosen because it changes color in a pH range between 8.3 – 10. It will show up as pink in basic solutions and clear in acidic solutions. Indicators such as methyl orange, change colour at around a pH of 4, far from where the equivalence point will occur. For weak acid-strong base reactions such as this experiment, phenolphthalein changes from colourless to pink as it was added to an acidic solution and neutralised by an alkaline solution.

However, due to the fact that ethanoic acid and sodium hydroxide have a proportional relationship, as seen from the ratio of 1:1, I expected roughly 25cm³ of sodium hydroxide to neutralise 25cm³ of 1/10 diluted vinegar. It is expected for 1 molecule of sodium hydroxide (NaOH) to react with 1 molecule of vinegar (HC2H3O2) to produce 1 molecule of salt, sodium acetate (NaC2H3O2), and 1 molecule of water (H2O).Therefore, the number of moles of base needed to react with all of the acid present is the same as the number of moles of acid present in the solution.

However, with my results obtained, I calculated an average of 29.7cm³ of sodium hydroxide needed to neutralise 25cm³ of vinegar. If the average was close to 25cm³ as suggested scientifically, than the calculation of ethanoic acid present in the diluted vinegar would have been lower and more valid. I have also discovered from this experiment that titration links to the outside world too and in most people's everyday lives. It can be used for medical purposes, for example, pharmacists use titration to achieve a desired mix of compound drugs. Doctors can use titration to find the correct amount of different medicines in an intravenous drip. Titration is also used to monitor blood glucose levels in patients who have diabetes, as well as in pregnancy tests and other ways of testing a patient's urine sample.

Furthermore, titration can be used in the food industry. It can be used to define oils, fats, and similar substances. Certain titration procedures are used to test free fatty acid content, unsaturated fatty acids and monitor and trace amounts of water. Titration can also be used to find the estimated chain length of fatty acids in a fat. Further uses of titration in the food industry include tests for the amount of salt or sugar, and the concentration of vitamin C or E, in a product. Titration is also used in wine and cheese production to test the product's readiness for human consumption.

Additionally, it can be used for science and education. Titration can be carried out in biology labs, where it is used to determine the concentration of chemicals to anesthetize test animals (give an anesthetic to the animal to make the animal endure the loss of consciousness.) Anesthetics are mixed and tested until the required compound appropriate to a given animal is successfully found. I also understood how helpful titration is in our own chemistry lessons. This is because titration is often used as a test of a student’s practical ability to carry out scientific investigations. It is a common, standard procedure, which requires adherence to instructions and proper use and handling of given substances, and titration’s easily measurable results can quickly show whether or not the experimental method was followed accordingly.

In conclusion, by doing this experiment I was able to determine the unknown volume of 0.1M sodium hydroxide (NaOH) needed to neutralize 25cm³ of 1/10 diluted vinegar. I found that approximately 29.7cm³ of sodium hydroxide is needed to neutralize the 25cm³ of vinegar. Most importantly, I was able to determine the percentage of ethanoic acid present in vinegar through calculations using known and unknown values. The percentage of ethanoic acid present is 1/10 diluted vinegar is roughly 7.1%. All objectives were met and so was the aim of the experiment.