34.05 mL of phosphorus vapour weigh 0.0625 g at `546^(@)C` and 1.0 bar pressure. What is the molecular mass of phosphorus? How many atoms are there in one molecule of phosphorus?

Answer

4

Explanation

Molecular mass of phosphorus, `M=(wRT)/(pV)`
`w=0.625g`,
`V=34.05mL=34.05xx10^(-3)L, p=1.0" bar"`
`T=273+546=819K, R="0.08314 L bar K"^(-1)"mol"^(-1)`
`M=(0.0625xx0.08314xx819)/(1xx34.05xx10^(-3))=124.9.`
Since atomic mass of phosphorus is 31,
No. of atoms of phosphorus in one molecule
`=(124.0)/(31)=4.`