Solutions and Colligative Properties - Result Question 28
27. The vapour pressure of pure benzene is $639.70$ $ mm$ of $Hg$ and the vapour pressure of solution of a solute in benzene at the same temperature is $631.9 $ $mm$ of $Hg$. Calculate the molality of the solution.
(1981, 3M)
Show Answer
Answer:
Correct Answer: 27. $(0.158)$
Solution:
According to Raoult’s law :
$ p=p _0 \chi _1 \Rightarrow 631.9=639.7 \quad \chi _1 $
$\Rightarrow \chi _1 =0.9878 \Rightarrow \chi _2=0.0122 $
$\Rightarrow \text { Molality } =\frac{0.0122}{0.9878 \times 78} \times 1000=0.158 $
BETA
