Hydrogen can be produced from water electrolysis. However for the design and control of this process, there is a need for an accurate model for the description of thermodynamic properties of electrolyte solutions such as activity coefficient. The Pitzer model has been applied in this work to correlate the mean ionic activity coefficient of a large number of aqueous electrolytes at 298.15 K using experimental data from literature. The model parameters of all the systems studied have been evaluated by minimizing the objective function using a computer code in FORTRAN language. The results show that this model can correlate the experimental data accurately. Moreover, the comparison of the average standard deviations of the fit obtained from this model and those obtained from the electrolyte NRTL, the TCPC, the electrolyte Wilson, the modified Wilson and the NRF-Wilson models indicate that the model applied in this work produces better accuracy. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.