Question

Vapour pressure of dilute aqueous solution of glucose is $750\, mm$ of mercury at $373\, K$. The mole fraction of solute is

• A. $ \frac{1}{76} $
• B. $ \frac{1}{7.6} $
• C. $ \frac{1}{38} $
• D. $ \frac{1}{10} $

Answer 1

Answer: (A)

At $373\, K \left(100^{\circ} C \right)$ V.P.
of water, $p ^{\circ}=760\, mm\,Hg , p_{s}=750\, mm\,Hg$
$\frac{p^{\circ}-p_{s}}{p^{\circ}}=x_{B}$
$\frac{760 -750}{760}=x_{B}$
$x_{B}=\frac{1}{76}$