부산대학교 도서관

Titrimetric methods were used to estimate the molar solubility and apparent acid dissociation constant (Kc) of salicylic acid in water. This was done with varied ionic strength values ranging from 0.00 to 0.75 mol·L−1 and over a temperature range of 15 to 60 °C. The thermodynamic dissociation constant (as pKa) of salicylic acid was found to be 2.985 at 25 °C. Within the measured temperature range, there was no consistent association between the pKa of salicylic acid and the temperature. The pKa values exhibited an inverse relationship with temperatures between 15 and 40 °C, while they showed a direct relationship with temperatures between 40 and 60 °C. Through the use of the Van’t Hoff plot, the standard thermodynamic quantities (∆H°, ∆S°, and ∆G°) for the dissociation process of salicylic acid in water were calculated. For temperatures between 15 and 30 °C, these values were determined as 3.346 kJ·mol−1, − 19.99 JK−1·mol−1, and 9.306 kJ·mol−1 respectively. For the temperature range of 45 to 60 °C, the values were calculated as − 1.499 kJ·mol−1, − 27.06 kJ·K−1·mol−1, and 6.564 kJ·mol−1. The heat of solution (∆Hsol°) was computed using the Van’t Hoff Isochore plot across the temperature range of 15 to 60 °C, resulting in a value of 15.03 kJ·mol−1.