The water activities of sodium molybdate in aqueous solutions at T = (303.15, 313.15, 323.15 and 333.15) K were determined, using vapor pressure osmometry. The range of salt concentration was from 0.06 to 2.2 mol kg(-1). The results show that sodium molybdate has a significant effect on the water activity. Values of the vapor pressure, osmotic and activity coefficient of the solutions were determined from the activity data. Finally, the studied system was modeled with the Pitzer model which allowed correlating the properties of these aqueous solutions obtaining a good agreement between the experimental data and the correlated values. (C) 2018 Elsevier B.V. All rights reserved.