`34.05 mL` of phosphorus vapours weighs `0.0625 g` at `546^(@)C` and `0.1` bar pressure. What is the molar mass of phossphorus ?

Explanation

`P=0.1 "bar"`
`V=34.05 mL=0.0336 L`
`R=0.0821 L atm K^(-1) mol^(-1)`
`T=273+546=819 K`
`PV=nRT`
`n=(PV)/(RT)=(0.1xx0.3405)/(0.0821xx819)=0.00005 mol^(-1)`
Molar mass of phosphorus is
`(0.0625 g)/(0.0005 mol^(-1))=125 g`