Second Virial Coefficients and Intermolecular Force Constants of the Ethane–Hydrogen Sulfide System

Abstract

Second virial coefficient data of ethane, hydrogen sulfide, and four mixtures of the two components at approximately equally spaced concentrations and at temperatures between 50 and 125°C were used for determining interaction second virial coefficients, evaluating the intermolecular force constants, and calculating the system second virial coefficients from the Lennard-Jones (6–12) and Stockmayer potentials. From second virial coefficient data between 25 and 200°C, the ethane force constants for the Lennard-Jones (6–12) potential were determined as ε / k = 219°K and σ = 4.59 Å, and the hydrogen sulfide force constants for the Stockmayer potential as ε / k = 194.5°K, σ = 5.15 Å, and t* = 0.1. Using the respective intermolecular potentials and force constants, it was found that the calculated second virial coefficients of ethane and hydrogen sulfide agreed with experimental data within 1% for the former and 2.5 to 4% for the latter. Because of the polarity of hydrogen sulfide, interaction second virial coefficients were calculated from the Lennard-Jones (6–12) potential using force constants obtained from modified mixing rules to account for the dipole–induced dipole interactions. The calculated interaction second virial coefficients differed from experimentally determined values by an average absolute deviation of 1.9% in the temperature range between 50 and 125°C. Experimental and calculated mixture second virial coefficients in the same region agreed within 2%.