The vapour pressure of `CS_(2)` at `50^(@)C` is `854 "torr"` and a solution of `2.0 g` sulphur in `100 g` of `CS_(2)` has vapour pressure `848.9 "torr"`. If the formula of sulphur molecule is `S_(n)`, then calculate the value of `n`. (at mass of `S = 32`).

Answer

`S_(8)`

Explanation

`(p^(@)-p_(s))/(p^(@))=(n_(2))/(n_(1))=(w_(2)//M_(2))/(w_(1)//M_(1)) " "therefore" "(854-848.9)/(854)=(2//M_(2))/(100//76)" "("Molecular mass of CS"_(2)=12+2xx32=76u)`
`"or "(5.1)/(854)=(2)/(M_(2))xx(76)/(100)" or "M_(2)=254.5u`
If formula of sulphur molecules is `S_(x)`, molecular mass `=x xx 32.` Hence, `32x=254.5 or x = 8.`