Sorption of CO, CH4, and N-2 in zeolite-X exchanged with different alkali metal ions was studied by volumetric measurements and Grand Canonical Monte Carlo simulation. CO and CH4 sorption is observed to show higher sorption capacity than N-2 in all cation exchanged zeolite samples. The adsorption capacity of CO in alkali metal exchanged zeolites is observed to decrease on moving from LiX to CsX, whereas for the methane adsorption capacity varies in reverse order. The isosteric heat of sorption data show stronger interactions of CO and N-2 molecules with alkali metal ion exchanged zeolites. The isosteric heat of CH4 show nearly same value (21-24 kJ/mol) for all alkali metal ion exchanged zeolites. Simulation of the CO and N-2 sorption in alkali metal zeolite -X clearly shows that the adsorbed CO and N-2 molecules are located in proximity to the extra-framework cations in the super cage. Simulated data of adsorption isotherms and heats of adsorption of CO, N-2, and CH4 in alkali metal ion exchanged zeolite-X agree reasonably well with the experimental results.