Apparent Molar Volume and Surface Tension of Dilute Aqueous Solutions of Carboxylic Acids

Density and surface tension of dilute aqueous solutions of propanoic, butanoic, pentanoic, and hexanoic acids have been measured at temperatures of (293.15, 298.15, 303.15, and 308.15) K. From experimental data apparent molar volumes and excess molar volumes were determined as a function of composition at each temperature. The limiting values of the partial volumes at infinite dilution of the acids in aqueous solution were determined at each temperature and the results were used to evaluate group contributions of the methylene and carboxylic groups. The surface tension measurements were used to evaluate the limiting experimental slopes of surface tension with respect to mole fraction. The influence of temperature on the behavior of volumetric and surface properties is discussed in terms of solute hydration and the balance between hydrophobic and hydrophilic interactions between the acids and water.