The cryoscopic constant for acetic acid is 3.6 K kg/mol. A solution of 1g of a hydrocarbon in 100 g of acetic acid freeze at `16.14^(@)"C"` instead of the usual `16.60^(@)"C"`. The hydrocarbon contains 92.3% carbon. What is the molecular formula?

Answer

`C_(6)H_(6)`

Explanation

Hydrocrabon-B ,acetic acid-A
`"m"_("B")=(1000"K"_("f")"w"_("B"))/("w"_("A")xxDelta"T"_("f"))`
`=(1000xx3.6xx1)/(100xx(16.60-16.14))`
`"m"_("B")=78 "gm"`
let molecular formula of Hydrocarbon`="C"_("x")"H"_("y")`
`12"x"+"y"=78`
`implies(12"x")/(78)xx100=92`
`implies" x"=(92xx78)/(12xx100)`
`"x=6(App)"`
`"y=6"`
`therefore"Molecular formula of compound"-"C"_(6)"H"_(6)`