`3.24 g` of sulphur dissolved in `400g` benzene, boiling point of the solution was higher than that of benzene by `0.081 K`. `K_(b)` for benzene is `2.53 K kg mol^(-1)`. If molecular formula of sulphur is `S_(n)`. Then find the value of `n`. (at.wt.of `S =32`).

Explanation

Let us first calculate the molar mass of sulphur ,
`M_(B) = (k_(b) xx 1000 xx w_(B))/(Delta T_(b) xx w_(A))`
`k_(b) = 2.53 Kg mol^(-1) , w_(B) = 3.24 g, w_(A) = 40 g , Delta T_(b) = 0.81 K`
`M_(B) = (2.53 xx 1000 xx 3.24)/(0.81 xx 40) = 253`
Let the molecular formula of sulphur = `S_(x)`
Atmoic mass of sulphur ` = 32`
Molecular mass ` = 32 xx x`
` 32 = 253`
` or " " x = 7.91 = 8`
`therefore ` Molecular formula of sulphur ` = S_(8)`