Abstract
A flow mixing calorimeter has been used to measure the excess molar enthalpy H m E of gaseous (water + hydrogen sulphide) at the mole fraction y=0.5, at standard atmospheric pressure, and over the temperature range 383.15 K to 483.15 K. Information about the strength of the (water + hydrogen sulphide) interaction was obtained by analysing the measurements using a quasi-chemical association model. The second virial coefficient B 11 of water was written B 11= B ns 11− RTK 11. The non-specific interaction B ns 11 between water molecules was calculated from the Stockmayer potential with parameters appropriate to a (water + non-polar fluid) interaction, and the specific (hydrogen bonding) forces were described by the association model in terms of an equilibrium constant K 11(298.15 K)=0.36 MPa −1 and an enthalpy of formation of ΔH 11=−(16.2±2) kJ· mol −1 for the (water + water) hydrogen bond. The second virial cross coefficient was written B 12= B 12 ns−( RTK 12)/2, and from the temperature dependence of ln K 12 the enthalpy of formation of the (water + hydrogen sulphide) interaction was found to be ΔH 12=−(12.0±2) kJ· mol −1 , and K 12(298.15 K)=0.1 MPa −1 . Values of the second virial cross coefficient are fitted by the equation B 12/(cm 3·mol −1)=56−53,100·(K/ T)−2.814·exp{1180·(K/ T)}.
Published Version
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