Measurement and Modelling of Water Activity, Density, Sound Velocity, Refractive Index and Viscosity of the Na2MoO4 + Poly(ethylene Glycol) + H2O System in the Temperature Range from 313.15 to 333.15 K

Thermodynamic and physical properties of water activity, density, sound velocity, refractive index and viscosity of unsaturated solutions of Na2MoO4 + PEG 4000 + H2O system and the constituent binary systems at 313.15, 323.15 and 333.15 K were studied. The concentration range of the solutions was from 0.02 to 0.17 mass fraction of Na2MoO4 and from 0.05 to 0.30 mass fraction of poly(ethylene glycol) with an average molar mass of 4000 g/mol. Water activities were correlated with the modified Pitzer model and physical properties were correlated by the Othmer's rule, obtaining in all cases a good agreement between the experimental and correlated data. Water activity predictions for the Na2MoO4 + PEG 2000 + H2O and Na2MoO4 + PEG 4000 + H2O systems were performed with the modified Pitzer and extended UNIQUAC models, respectively, showing that both thermodynamic models can operate independently of the molar mass of the polymer used. (C) 2020 Elsevier B.V. All rights reserved.