Recommended Activity Coefficients and Equivalent Conductivities of Aqueous Hydrochloric Acid in the Concentration Range 5 x 10(-6)-10(-1) M and Temperature Range 5-55 degrees C Based on the DH-SiS and DHO-SiS Theoretical Treatments

摘要

Thermodynamic properties of aqueous HCl are of great importance in science, technology, and engineering. Ample experimental data exist on the activity and conductivity of the acid, and empirical expressions are offered as interpolation equations for computing those data at the desired concentration and temperature. The DH-SiS theory (Fraenkel Mot. Phys. 2010, 108, 1435), extending the Debye-Hiickel theory by considering the smaller-ion shell (SiS) around the chosen ion, has afforded successful fit to activity coefficients of aqueous and nonaqueous HCl solutions (Fraenkel J. Phys. Chem. B 2011, 115, 557, 14634). Here, I analyze equivalent conductivities of the acid by the DHO-SiS theory (Fraenkel Phys. Chem. Chem. Phys. 2018, 20, 29896) that incorporates the SiS concept into the Debye-Hiickel-Onsager theory. The interrelation of DHO -SiS and DH-SiS allows computation of activity from conductivity and vice versa. Thus, I propose recommended values of activity coefficients, equivalent conductivities, and pH of HCl(aq) within the concentration and temperature ranges of the paper's title. These theoretical values accurately reproduce the corresponding experimental values, but they stem from analytic mathematical equations with no adjustable parameters, instead of from empirical or semiempirical expressions containing adjustable parameters and/or coefficients of no clear physical meaning.