Question

The vapour pressure of a dilute aqueous solution of glucose is $750$ mm of $Hg$ at $373$ K. The mole fraction of solute is:

• A. $\frac{1}{10}$
• B. $\frac{1}{7.6}$
• C. $\frac{1}{35}$
• D. $\frac{1}{76}$

Answer 1

The correct option is D $\frac{1}{76}$

$P$ of solution $=750mm$

$P_0$ of solution $=760mm$ ( atmospheric pressure )

$\therefore$ Change in pressure, ie, $\Delta P=P_0-P$

$=(760-750)mm$ of $Hg$

$=10mm$ of $Hg$

And we know,

Hole fraction of solute $=\frac{\Delta P}{P_0}=\frac{10}{760}$

$=\frac{1}{76}$