An evacuated glass vessel weighs 50.0 g when empty. It weighs 148.0 g when filled with a liquid of density 0.98g(mL)− and 50.5 g when filled with an ideal gas at 760 mm Hg at 300 K. Determine the molecular weight of the gas.

wt. of empty vessel = 50 gwt. of empty vessel+ wt. of liquid= 148 g ∴ wt. of liquid = 148 g- 50 g = 98 g.Density of liquid 0.98g(mL)−.∴ Volume of vessel= Volume of liquid = wt.  density =98g0.98g(mL)−                                                             =100mLwt. of ideal gas + wt. of empty vessel  = 50.5 g ∴ wt. of ideal gas = 50.5 - 50 = 0.5 g;PV=WMRTM=0.5g×0.0821LatmK−mol−×300K1atm×0.1L=123.15gmol−