2022 IB Diploma Extended Essays

results whilst having a more significant change of colour at its endpoint. Finally, for the pH data logger method, I used the pH of 8.2 as the endpoint after researching it and confirming it through trials where I did the titration with the pH logger and with indicators to consistently compare the pH and the colour of the wine throughout (Ferguson, n.d.). 1.3 Identification and Exploration of the Investigation Titratable Acidity (TA) Titratable acidity (TA) is the number of protons from all acids, except carbonic acids (H 2 CO 3 , H 2 0 and CO 2 ), that can be recovered from a solution that can neutralise with a strong base (disassociated protons- will be further explained later). As wine has a wide range of acids, tartaric acid will be referred to when determining the TA since it is the primary acid in wine (Petrović, 2007) . The titration methods used in this investigation will result in a volume of NaOH, which was found to neutralise the 20ml sample of the wine entirely. The volume will then be substituted into equation 1 (Bylikin, et al., 2014) to find the moles of NaOH used. Equation 1: = As mentioned previously, the ratio between NaOH and tartaric acid is 1:2. Therefore, the number of moles of tartaric acid is half of NaOH. The mass of tartaric acid can then be calculated using equation 2 (Bylikin, et al., 2014). Equation 2: = × By dividing the mass of tartaric acid by the volume of the wine sample, the amount of tartaric acid per ml can be defined (equation 3). However, the equation below can be expanded into equation 4 to calculate the TA in one step. Equation 3: = Equation 4: = (0.5× × ) Total Acidity Total Acidity is the sum of both dissociated and undissociated protons (hydrogen ions) from the organic acid anions (lactic, citric, acetic, sulphurous acids etc.) in the solution, wine. Dissociated means that the protons would split from their atom to form an ion with the water in its solution (Bylikin, et al., 2014). As Total Acidity includes protons that would and wouldn’t split, it’s value will always be higher than the TA. Therefore, to calculate the accuracy of the four methods, the total acidity will be calculated and considered as the theoretical value in the adapted percentage accuracy seen in equation 5 (Boulton, 1980). To calculate the theoretical total acidity, the pH of the wine can be used to find the concentration of hydrogen ions, as seen in the equation below. Equation 5: = 2×10 −