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The vapour pressure of solvent is 20 tor...

The vapour pressure of solvent is 20 torr, while that of its dilute solution is 17 torr , the mole-fraction of the solvent is

A

0.6

B

0.4

C

0.85

D

0.7

Text Solution

Verified by Experts

The correct Answer is:
C
Vapour pressure of solvent `"p"^(@)=20"torr"` and vapour pressure of solution `"p"_(s)=17"torr".`
Therefore,`("P"^(@)-"P"_(s))/"P"^(@)="mole fraction of solute"`
Or `(20-17)/20=0.15="mole fraction of solute"`
Mole fraction of solvent`=1-0.15=0.85`
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