The inhibition of gas hydrate (clathrate hydrate) formation plays an important role in petroleum industries. A way to prevent this problem is injecting chemical inhibitors to the transportation pipelines. Two typical kinds of chemical inhibitors are thermodynamic and kinetic inhibitors. The main goal of the current work is to provide a thermodynamic model without using any adjustable parameters for prediction of the dissociation conditions of hydrate for pure and mixed gases including several thermodynamic inhibitors of ethylene glycol (EG), methanol (MeOH), potassium chloride (KCl), calcium chloride (CaCl2), and sodium chloride (NaCl). For this purpose, application of the extended UNIQUAC activity coefficient model along with the van der Waals-Platteuw solid solution theory has been proposed. A comprehensive literature survey has been performed to provide a complete set of experimental data, and 1455 data points have been provided. Comparing the current model results with the experimental data reported in literature, the average absolute deviations (AAD) is 0.50 K which shows the accuracy of the results of the model developed in the current study.