Apparent molar volumes and apparent molar heat capacities of aqueous phenol and sodium phenolate at temperatures from 278.15 to 393.15 K and at the pressure 0.35 MPa
Résumé
Apparent molar volumes Vφ and apparent molar heat capacities Cp,φ have been determined for aqueous solutions of phenol (C6H5OH) and its sodium salt (C6H5ONa) at temperatures T from 278.15 to 393.15 K, at the pressure 0.35 MPa, and at molalities m from 0.025 to 0.50 mol·kg−1. We used a vibrating tube densimeter (DMA 512P, Anton PAAR, Austria) to determine the densities and volumetric properties, and a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corporation, American Fork, UT, USA) to obtain the heat capacities. Infinite dilution partial molar volumes V20 and heat capacities C0p,2 were obtained over the range of temperatures by extrapolation to m=0 mol·kg−1 on the fitted surfaces (Vφ,T,m) and (Cp,φ,T,m). Our results were combined with values of Vφ and Cp,φ from the literature for NaCl(aq), HCl(aq), and NaOH(aq) to obtain (ΔrVm,T,m) and (ΔrCp,m,T,m) for the proton dissociation reaction of C6H5OH(aq). Surfaces representing (ΔrHm,T,m), (pQa,T,m), and (ΔrSm,T,m) where created by integration of our (ΔrCp,m,T,m) surface using values for (ΔrHm,m) and (pQa,m) at T=298.15 K from the literature as integration constants.