Question

The normal
Freezing point nitrobenzene is
278.82 K 4. 0.25 molal-solution of
certain
solute in nitrobenzene causes
OF freezing point depression of 2degree C.
calculate value of Kf
for nitrobenzene.
​

Answer 1

Given

0.25 molal solution of certain solute depresses the freezing point of nitrobenzene by 2° C.

To Find

The cryoscopic constant $K_f$

Formula

Depression in freezing point :- $\Delta T_f\:=\:K_f\:\times\:m$ where, m is molality .

Calculations

We have,

$\Delta T_f\:=\:2\\ \\m\:=\:0.25\\ \\ \textsf{using the formula} \\ \\ => \: \Delta T_f\:=\:K_f\:\times\:m \\ \\ => \: 2\:=\:K_f\:\times\:0.25 \\ \\ => \: K_f\:= \: \dfrac{\cancel{2}\:8}{\cancel{0.25}} \\ \\ \\ => \: K_f\:=\:8$

$\boxed{\boxed{\green{\textsf{The value of cryscopic constant is 8 units.}}}}$