An evacuated glass vessel weighs 40 . 0 g when empty, 135 . 0 g when filled with a liquid of density 0 . 95 g mL - 1 and 40 . 5 g when filled with an ideal gas at 0 . 82 atm at 250 K . The molar mass of the gas in gmol - 1 is : (Given : R = 0 . 082 L atmK - 1 mol - 1 )

Step-by-step solution

Weight of gas = 40 . 5 - 40 = 0 . 5   g Mass of liquid = 135 . 5 - 40 = 95   g . Volume of glass vessel = 95 . 0   g 0 . 95   g / ml = 100 ml . ∴   PV = W M RT 0 . 82   atm 100 × 10 - 3 = 0 . 5 M 0 . 082 250 M = 125   g / mol