Thermodynamic Van’t Hoff Equation in Aqueous Dissociation of Benzoic Acid at Ordinary Temperature Range

In this chapter, authors reported on the use of the thermodynamic Van't Hoff equation in the investigation of the dissociation process of solute benzoic acid into water solvent at ordinary temperatures ranging from 288 K to 318 K. At this temperature range, the value of dissociation constant (Kc) of that acid is being to found as -4.169, -4.045, -3.993, -3.885, -3.848 and -3.788, for given concentrations of NaCl (sodium chloride) volume as its six ionic strength of 0.00, 0.05, 0.10, 0.30, 0.40 and 0.50 M, respectively, which are titrimetrically analyzed with 0.05 M basic NaOH (sodium hydroxide) solution. A digital pH-meter is also used to determine the pH of each solution. The pH value of benzoic acid in water at that temperature range is inversely related to NaCl concentrations, according to this observation. A value of benzoic acid with its ionic strength (I) is shown against the equilibrium dissociation constant (Kc) at a temperature of 298 K, demonstrating that the dissociation of acid into water increases as the ionic strength increases. However, the graph for extending the temperature range to the thermodynamic dissociation constant (Ka) has revealed that the dissociation does not necessarily rise as the temperature increases.