On dissolving 3.24 g of sulphur in 40 g of benzene, boliling point of the solution was highter then that of benzene by 0.81 K. The molal elevation constant `(K_(b))` for benzeneis 2.53 K kg `mol^(-1)`. `"What is the molecular formula of sulphur "("Atomic mass of" S=32 g mol^(-1))?`

Explanation

Calculation of molecular mas of sulphur `(S_(n))`
`M_(B)=(K_(b)xxW_(b))/(DeltaT_(b)xxW_(A))`
Mass of sulphur `(W_(b))=3.24g`
`" Mass of benzene"(W_(A))=40g=0.04 kg`
Molal elevetion constant `(K_(b))=2.53 K kg mol^(-1)`
Elevation in boiling point `(Delta T_(b))=0.81 K`
`M_(B)=((2.53 K kg mol^(-1))xx(3.24 g))/((0.81 K)xx(0.04 kg))=253g mol^(-1)`
Calcultion of molecular formula of sulphur.
Gram atomic mass of sulphur =32 g `mol^(-1)`
In `S_(n),nxx(32g mol^(-1))=253 g mol^(-1)`
`n=((253 g mol^(-1)))/((32g mol^(-1)))=7.9~~8`
Molecular formula of sulphur is `S_(8)`.