Solutions Question 130
Question: The vapour pressure of a solvent decreased by $ 10mm $ of mercury, when a non-volatile solute was added to the solvent. The mole fraction of the solute in the solution is 0.2. What should be the mole fraction of the solvent, if decrease in the vapour pressure is to be $ 20,mm $ of mercury [CBSE PMT 1998]
Options:
A) 0.8
B) 0.6
C) 0.4
D) 0.2
Show Answer
Answer:
Correct Answer: B
Solution:
\ $ P^{0}-P_{s}=P^{0}\times \text{mole },fraction,\text{ solute} $
$ 10=P^{0}\times 0.2 $ ; $ 20=P^{0}\times n $
Þ $ n=0.4 $ \ $ N=0.6 $ .
