Chemical Engineering - Stoichiometry - Discussion

Discussion Forum : Stoichiometry - Section 6 (Q.No. 20)
20.
The vapor pressure of the solvent decreased by 10 mm Hg, 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 the decrease in vapor pressure of the solvent is required to be 20 mm Hg. ?
0.2
0.1
0.4
0.6
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
2 comments Page 1 of 1.

TANMAY SHAH said:   2 years ago
Please anybody explain the answer with calculation.

Ramsajan said:   2 years ago
According to Roults law, the partial pr(Pa) is directly proportional to the mole fraction in the liquid phase at equilibrium Pa=pa°Xa.
Here pa° => vapour pressure of that component at the same temp.
Then Xa=1/pa°
xa2 = pa°1/pa°2*xa ==> 10/20 *0.8.
then ans will be 0.4. right?

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