2022 IB Diploma Extended Essays

1.4 Hypothesis If the TA of white wine is experimentally determined through various titration methods against 0.1M NaOH, then the titration method using the pH data logger should result in the most accurate TA value. In theory, all methods should obtain correct results, but this investigation aims to determine the accuracy of these results. The pH of the solution is measured every second through the pH sensor. Therefore, the endpoint can be digitally detected, and the titration can stop as soon as it reaches a pH of 8.2. The TA calculated should be closer to the Total acidity than the TA found through the other methods. In addition, the other titration methods require the human eye to detect if the solution has changed colour visually. Because of this, the titration could be stopped too late, and the solution would have excess base. Therefore, the titration with the pH sensor should have the most accurate result. 2. Design 2.1 Variables Variable How and why, it was manipulated Independent Method used to find the TA of white wine 2/3 methods were used: titration with

bromothymol blue, titration with phenolphthalein and potentiometric titration The titration resulted in the volume of NaOH the fully neutralised the wine. With the volume, equation 4 can be solved and thus the TA is found. The experiment was performed in standard lab conditions. All trials were done in the same room, staying away from any windows, and the air conditioner was turned off. Why: The temperature of the environment can affect the 6 trials were done for each method Why: To have a fair test between each method. The wine was collected from bottles from the same manufacturer, year it was made and type (white wine). 20ml of the wine was measured using a 20ml volumetric pipette. Why: White wine was used as it is more acidic than red wine which will produce a more extensive titration curve thus resulting in a more accurate experiment. By keeping the

Dependent

The TA found from each method

Controlled

Surrounding conditions

Number of trials

Volume, concentration, type and make of the wine