2022 IB Diploma Extended Essays

Graph 1: Comparison of the Titratable Acidity found through Titration with Phenolphthalein Indicator, Bromothymol Blue, Back Titration with bromothymol Blue and Titration with a pH Logger

Titratable Acidity found from Different Titrations vs. the theoretical Total Acidity

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05 Titratable Acidity (moldm -3 )

method 1: Phenolphthalein Pink method 2: Bromothymol Blue method 3: Back Titration with Bromothymol Blue method 4: Titration with pH Data Logger Theoretical Total Acidity

3.3 Analysis In response to the research question, ‘How do various titration methods compare to Total Acidity value when titrating tartaric acid against NaOH to determine the TA of the wine’, the investigation proved that titration with pH logger was the most accurate in determining the TA of the white wine. As seen in Graph 1, most of the methods resulted in a TA value that was much lower than the theoretical Total Acidity value. Total Acidity value. This trend is supported as Total Acidity is the sum of dissociated and undissociated protons. As TA measures the protons that can be recovered, it is unable to account for both dissociated and undissociated protons. Therefore, the TA values should be lower than the Total Acidity. The graph along with processed data table 2, shows that Method 2 is the least accurate whilst method 4 has the highest percentage accuracy of 83.4%. This means that the titration with the pH sensor was able to measure the most protons in the wine, making the method the most precise. Furthermore, the rest of the methods’ accuracy are 10% lower; Method 1 has a percentage accuracy of 65.9% and method 3 is 70.5% accurate. A reason for methods 1,2 and 3 having significant difference with the accuracy of method 4, was that the endpoint was decided through seeing the wine’s colour change. This proves that determining the wine’s endpoint numerically was more efficient. The uncertainty of the methods is not significant to the results of the experiment. All uncertainties lie between 7 ×10−4 and 1.00×10−3 mol −3 thus only making a minuscule difference to the TA values. The overall small uncertainties prove the investigation’s reliability as the trials’ results maintained consistent, reducing the error within each titration method.