An evacuated glass vessel weighs `50.0 g` when empty, `148.0 g` when filled with a liquid of density `0.98 g mL^(-1)`, and `50.5 g` when filled with an ideal gas at `760 mm Hg` at `300 K`. Determine the molar mass of the gas.

Explanation

Weight of liquid `=148 -50 =98 g`
Volume of liquid ` =(8)/(0.98) = mL ` = volume of vessel
Thus, a vessel of `100mL` contains ideal gas at `760 mm` of Hg at `300K`
Weight of gas ` =50.5 - 50 =0.5 g`
Using `PV =nRT`
`(760)/(760) xx (100)/(1000) = (0.5)/(m) xx 0.0821 xx 300`
`:.` Molecular weight of gas `(m) =123` .