The normal freezing point of nitrobenzene `(C_(6)H_(5)NO_(2))` is `278.82K`. `A 0.25` molal solution of a certain solute in nitrobenzene causes a freezing point depression of `2` degrees. Calculate the value of `K_(f)` for nitrobenzene.

Explanation

Given Normal freezing point of nitrobenzene `(C_(6)H_(5)NO_(2))=278.82K`
molality of solution `=0.25m`
Freezing point depression `=2` degrees
Asked Cryoscopic constant `=?`
Formulae: `DeltaT_(f)=K_(f)xxm`
Explanation: `DeltaT_(f)=` Freezing point depression
`K_(f)=` cryoscopic constant
`m=` molality of solution
Substitution `&` Calculation
`2=K_(f)xx0.25`
`K_(f)=(2)/(0.25)=8K kg "mol"^(-1)`