34.5 mL of phosphorus vapour weights 0.0625g at `546^@C` and 0.1 bar pressure . What is the molar mass of phosphorus?

Explanation

Mole of phophorus vapour (n) `=(pV)/(RT)`
`=(1 ba r times34.05times10^-3L)/(0.0831ba r Lk^-1mol^-1times819.15k)`
`=5.0 times 10^-4`
Let molar mass of phosphorus be M `gmol^-1`
`therefore ` Mole of phosphorus vapour =`0.0625/M`
Now, `0.0625/M=5.0 times 10^-4` (or)
`M=0.0625/(5.0 times 10^-4) =125 gmol^-1`